tuberculosis

(TB), contagious, wasting disease caused by any of several mycobacteria. The most common form of the disease is tuberculosis of the lungs (pulmonary consumption, or phthisis), but the intestines, bones and joints, the skin, and the genitourinary, lymphatic, and nervous systems may also be affected.

There are three major types of tubercle bacilli that affect humans. The human type (Mycobacterium tuberculosis), first identified in 1882 by Robert KochKoch, Robert
, 1843–1910, German bacteriologist. He studied at Göttingen under Jacob Henle. As a country practitioner in Wollstein, Posen (now Wolsztyn, Poland), he devoted much time to microscopic studies of bacteria, for which he devised not only a method of
..... Click the link for more information. , is spread by people themselves. It is the most common one. The bovine type (M. bovis) is spread by infected cattle but is no longer a threat in areas where pasteurization of milk and the health of cattle are strictly supervised. The avian type (M. avis) is carried by infected birds but can occur in humans. The tubercle bacillus can live for a considerable period of time in air or dust. The most common means of acquiring the disease is by inhalation of respiratory droplets.

Course of the Disease

Tuberculosis of the lungs usually results in no or minimal symptoms in its early stages. In most persons the primary infection is contained by the body's immune system, and the lesion, called a tubercle, becomes calcified. In many the infection is permanently arrested. In others the disease may break out again and become active years later, usually when the body's immune defenses are low. Untreated, the infection can progress until large areas of the lung and other organs are destroyed. Symptoms of the disease include cough, sputum, bleeding from the lungs, fever, night sweats, loss of weight, and weakness.

Incidence

The incidence of tuberculosis of the lungs, the "white plague" that formerly affected millions of people, declined in the United States from the 1950s until 1984; sanatoriums were closed and routine screening was abandoned. Then, between 1984 and 1992, the incidence increased by 20%, chiefly because of immigration from countries where it is common and because of AIDSAIDS
or acquired immunodeficiency syndrome,
fatal disease caused by a rapidly mutating retrovirus that attacks the immune system and leaves the victim vulnerable to infections, malignancies, and neurological disorders. It was first recognized as a disease in 1981.
..... Click the link for more information. , which leaves people particularly vulnerable to the disease. Renewed efforts at control and advances in treatment have been rewarded with incidence declines since 1993.

Worldwide the outlook has been far less encouraging. In 1993 the World Health Organization (WHO) declared TB a global health emergency. Approximately one third of the world's population is infected; an estimated 1.3 million died in 2012, making tuberculosis one of the most deadly infectious diseases. The vast majority of new cases occur in sub-Saharan Africa. Spread of TB is especially rapid in areas with poor public health services and crowded living conditions. In homeless shelters and prisons, crowded conditions and inadequate treatment often go together. Areas where living conditions are disrupted by wars, famine, and natural disasters also are heavily affected.

Especially alarming has been the spread of drug-resistant strains of TB. By the late 1990s scientific experts and international health officials warned that drug-resistant strains were spreading faster than had been anticipated. Bacteria can survive and become drug resistant in patients whose treatment is not properly monitored and seen to completion. Multidrug resistant (MDR) TB strains are resistant to two or more of the commonly prescribed first-line drugs, while extensively drug resistant (XDR) strains are also resistant to three or classes of the more toxic second-line drugs. Some believe that unless major new treatment strategies are initiated in source countries, drug-resistant TB will eventually become epidemic even in areas with good control programs, such as Europe and America. In 2011, WHO estimated that there were more than 80,000 cases, many of them undiagnosed, of drug-resistant TB in Europe.

Diagnosis and Treatment

Diagnosis is made by a tuberculin skin test. It can be confirmed by X raysX ray,
invisible, highly penetrating electromagnetic radiation of much shorter wavelength (higher frequency) than visible light. The wavelength range for X rays is from about 10⁻⁸ m to about 10⁻¹¹
..... Click the link for more information. of the chest and sputum examination. Ideally, treatment begins after a skin test signals exposure but before active disease has developed. The treatment of choice for prevention and for active cases is the antimicrobial drug isoniazidisoniazid
, drug used to treat tuberculosis. Also known as isonicotinic acid hydrazide, isoniazid is the most effective antituberculosis drug currently available. The drug inhibits or kills the tubercle bacilli that cause the disease.
..... Click the link for more information. (INH), available since 1956. In infected individuals it now is usually used in combination with other antituberculosis drugs such as rifampin, pyrazinamide, and ethambutol. Bedaquiline is used to treat multidrug resistant and extensively drug resistant TB.

Tuberculosis drugs have to be taken regularly, typically for 6 to 12 months. Many patients abandon their treatment when they feel better; similarly, preventive treatment is often abandoned because of the inconvenience. Such noncompliance is believed to be the main reason for the upsurge in drug-resistant strains of the TB bacilli, many of which are resistant to more than one drug. Drug-resistant TB is difficult to treat and has a much higher death rate; extensively resistant TB is especially worrisome because it can be essentially untreatable.

The combination drug rifater (rifampin, isoniazid, and pyrazinamide) has simplified drug administration. Directly observed treatment, where health-care workers watch patients take each dose of medicine, has proved effective in eliminating the problem of noncompliance in the United States, but monitoring has been less effective in many other parts of the world.

Prevention of Tuberculosis

Preventive measures include strict standards for ventilation, air filtration, and isolation methods in hospitals, medical and dental offices, nursing homes, and prisons. If someone is believed to have been in contact with another person who has TB, preventive antibiotic treatment may have to be given. Infected persons need to be identified as soon as possible so that they can be isolated from others and treated.

An antituberculosis vaccine, bacille Calmette-Guérin, or BCG vaccine, was developed in France in 1908. Although there is conflicting evidence as to its efficacy (it appears to be effective in 50% of those vaccinated), it is given to over 80% of the world's children, mostly in countries where TB is common; it is not generally given in the United States. Federal health officials in the United States have stated (1999) that a new vaccine is essential to TB prevention. It is hoped that the determination of the complete DNA (genome) sequence of Mycobacterium tuberculosis, achieved in 1998, will hasten the development of an effective vaccine.

Bibliography

See R. Dubos, The White Plague (1955); S. A. Waksman, The Conquest of Tuberculosis (1964); K. Lougheed, Catching Breath: The Making and Unmaking of Tuberculosis (2017).

Tuberculosis

An infectious disease caused by the bacillus Mycobacterium tuberculosis. It is primarily an infection of the lungs, but any organ system is susceptible, so its manifestations may be varied. Effective therapy and methods of control and prevention of tuberculosis have been developed, but the disease remains a major cause of mortality and morbidity throughout the world. The treatment of tuberculosis has been complicated by the emergence of drug-resistant organisms, including multiple-drug-resistant tuberculosis, especially in those with HIV infection. See Acquired immune deficiency syndrome (AIDS)

Mycobacterium tuberculosis is transmitted by airborne droplet nuclei produced when an individual with active disease coughs, speaks, or sneezes. When inhaled, the droplet nuclei reach the alveoli of the lung. In susceptible individuals the organisms may then multiply and spread through lymphatics to the lymph nodes, and through the bloodstream to other sites such as the lung apices, bone marrow, kidneys, and meninges.

The development of acquired immunity in 2 to 10 weeks results in a halt to bacterial multiplication. Lesions heal and the individual remains asymptomatic. Such an individual is said to have tuberculous infection without disease, and will show a positive tuberculin test. The risk of developing active disease with clinical symptoms and positive cultures for the tubercle bacillus diminishes with time and may never occur, but is a lifelong risk. Only 5% of individuals with tuberculous infection progress to active disease. Progression occurs mainly in the first 2 years after infection; household contacts and the newly infected are thus at risk.

Many of the symptoms of tuberculosis, whether pulmonary disease or extrapulmonary disease, are nonspecific. Fatigue or tiredness, weight loss, fever, and loss of appetite may be present for months. A fever of unknown origin may be the sole indication of tuberculosis, or an individual may have an acute influenzalike illness. Erythema nodosum, a skin lesion, is occasionally associated with the disease.

The lung is the most common location for a focus of infection to flare into active disease with the acceleration of the growth of organisms. There may be complaints of cough, which can produce sputum containing mucus, pus- and, rarely, blood. Listening to the lungs may disclose rales or crackles and signs of pleural effusion (the escape of fluid into the lungs) or consolidation if present. In many, especially those with small infiltration, the physical examination of the chest reveals no abnormalities.

Miliary tuberculosis is a variant that results from the blood-borne dissemination of a great number of organisms resulting in the simultaneous seeding of many organ systems. The meninges, liver, bone marrow, spleen, and genitourinary system are usually involved. The term miliary refers to the lung lesions being the size of millet seeds (about 0.08 in. or 2 mm). These lung lesions are present bilaterally. Symptoms are variable.

Extrapulmonary tuberculosis is much less common than pulmonary disease. However, in individuals with AIDS, extrapulmonary tuberculosis predominates, particularly with lymph node involvement. Fluid in the lungs and lung lesions are other common manifestations of tuberculosis in AIDS. The lung is the portal of entry, and an extrapulmonary focus, seeded at the time of infection, breaks down with disease occurring.

Development of renal tuberculosis can result in symptoms of burning on urination, and blood and white cells in the urine; or the individual may be asymptomatic. The symptoms of tuberculous meningitis are nonspecific, with acute or chronic fever, headache, irritability, and malaise.

A tuberculous pleural effusion can occur without obvious lung involvement. Fever and chest pain upon breathing are common symptoms.

Bone and joint involvement results in pain and fever at the joint site. The most common complaint is a chronic arthritis usually localized to one joint. Osteomyelitis is also usually present.

Pericardial inflammation with fluid accumulation or constriction of the heart chambers secondary to pericardial scarring are two other forms of extrapulmonary disease.

The principal methods of diagnosis for pulmonary tuberculosis are the tuberculin skin test (an intracutaneous injection of purified protein derivative tuberculin is performed, and the injection site examined for reactivity), sputum smear and culture, and the chest x-ray. Culture and biopsy are important in making the diagnosis in extrapulmonary disease.

A combination of two or more drugs is used in the initial therapy of tuberculous disease. Drug combinations are used to lessen the chance of drug-resistant organisms surviving. The preferred treatment regimen for both pulmonary and extrapulmonary tuberculosis is a 6-month regimen of the antibiotics isoniazid, rifampin, and pyrazinamide given for 2 months, followed by isoniazid and rifampin for 4 months. Because of the problem of drug-resistant cases, ethambutol can be included in the initial regimen until the results of drug susceptibility studies are known. Once treatment is started, improvement occurs in almost all individuals. Any treatment failure or individual relapse is usually due to drug-resistant organisms. See Drug resistance

The community control of tuberculosis depends on the reporting of all new suspected cases so case contacts can be evaluated and treated appropriately as indicated. Individual compliance with medication is essential. Furthermore, measures to enhance compliance, such as directly observed therapy, may be necessary. See Mycobacterial diseases

Tuberculosis

an infectious disease of animals and man that tends to be chronic and that causes inflammatory changes, often in the form of small tubercles located mainly in the lungs and lymph nodes.

Tuberculosis of man is the concern of the medical discipline known as phthisiology. Descriptions of tuberculosis symptoms are found in ancient Egyptian papyri and Indian manuscripts, in the works of Hippocrates and other physicians, and in the writings of ancient priests and classical poets. Traces of tuberculosis have been found in Egyptian mummies dating from 3000 to 2000 B.C.. Avicenna (tenth-llth centuries A.D.) noted the extensive occurrence of the disease.

In 17th- and 18th-century London, mortality from tuberculosis reached 700 to 870 per 100,000 inhabitants annually. The rates were comparable in Hamburg, Stockholm, and other large European cities, where tuberculosis accounted for approximately 20 to 40 percent of all deaths. In prerevolutionary Russia, mortality from tuberculosis in Moscow and St. Petersburg was 467 and 607 per 100,000 inhabitants, respectively (1881). Factory workers were particularly susceptible to “the cellar-dweller disease, ” as tuberculosis was called. The mortality from tuberculosis among St. Petersburg workers from 1910 to 1916 was three to five times higher than among the city’s more well-to-do population. A sharp increase in the incidence and mortality rates of tuberculosis occurred everywhere during socioeconomic crises and wars.

The incidence of tuberculosis, as well as its morbidity and mortality, have declined in the economically developed countries owing to improved living conditions and sanitation and the use of effective measures of prevention and treatment. However, the extent of the decline varies from country to country and among different age, sex, and social groups within the same country. For example, the incidence of tuberculosis per 100,000 population in 1969–70 was 60.3 in the German Democratic Republic (GDR), 71.9 in France, 81.5 in the Federal Republic of Germany (FRG), and 199.0 in Japan. The mortality per 100,000 population in 1970 was 5.4 in the GDR, 8.2 in France, 15.3 in Japan, 36 in Hong Kong, and 82 in the Philippines.

In the USA, the incidence and mortality rates of tuberculosis among Negroes, Indians, Puerto Ricans, and other nonwhite groups are three to four times higher than among whites. Among whites, the rates are highest for unskilled laborers and low-salaried employees. In France, the mortality from tuberculosis is three to five times higher among miners, sailors, and fishermen than among persons engaged in the professions, highly paid government employees, and industrial managers. In Paris, the risk of contracting tuberculosis is 25 times higher for immigrant workers from Portugal and Yugoslavia than for native Parisians, and 30 to 50 times higher for Africans (1969–70). Incidence and mortality are high among New Zealand aborigines and among Australian aborigines relocated to regions in the northern and western parts of the country, where living conditions are unfavorable.

No statistics on the incidence and mortality rates for tuberculosis existed in many developing countries of Africa, Asia, and Latin America by the mid-1970’s. Medical examinations of the inhabitants of some areas of these countries have been conducted by personnel of the World Health Organization (WHO) since 1951. The results of these examinations have revealed a high incidence of all forms of tuberculosis, including severe and progressive forms. In India alone, according to approximate calculations, 7 to 10 million persons have bacillary pulmonary tuberculosis. According to WHO estimates, tuberculosis holds third or fourth place among the main causes of death in many developing countries, as compared to eighth or ninth place in economically developed countries.

In the USSR, all the indexes of tuberculosis, especially among children and adolescents, have declined sharply owing to the higher standard of living and the implementation of measures of prevention and treatment on a nationwide scale. In 1972, the incidence and mortality rates of tuberculosis in the USSR had declined by a factor of two as compared to the 1960 levels. Disability from the disease had declined by a factor of almost five. The USSR exhibits a pattern typical of economically developed countries: the sharpest decline in the indexes of tuberculosis was observed in children, adolescents, and young adults, and more among females than among males. The age differences result from the use of the antituberculosis vaccine BCG, of preventive drugs, and of other preventive measures among children and adolescents. The sex differences are caused by the lower incidence among women of such harmful habits as alcohol abuse and smoking.

Mechanisms of infection and pathogenesis. Long before the Common Era, it was believed that tuberculosis was an infectious disease, but it was not until 1865 that the French physician J. A. Villemin proved that it is caused by an infectious agent. In 1882, R. Koch discovered the causative agent, the tubercle bacillus—a sometimes granular bacillus in the shape of a straight or slightly bent rod 1.5–3 micrometers long. The bacillus occurs in filtrable and atypical forms. L-shaped forms have been isolated; these have partly or completely lost their cell wall but are capable of reproducing and, under favorable conditions, of reverting to the classical tubercle bacillus.

All forms of the bacillus are tuberculosis mycobacteria and occur in human, bovine, and avian varieties. The human variety, Mycobacterium tuberculosis var. hominis, infects mainly man. The bovine variety, M. tuberculosis var. bovis, is pathogenic for man as well, but more commonly infects animals. The avian variety, M. avium, infects mainly poultry. In cases of pulmonary tuberculosis in which the causative agent can be isolated, the human variety of the bacillus is found in the sputum and other excretions in 90 to 95 percent of the cases; the bovine variety is found in the remaining 5 to 10 percent of the cases. The bovine variety is somewhat more common in nonpulmonary tuberculosis. The frequency of infection in man by the bovine or avian variety depends on the extent of the infection among domestic animals and poultry, and on the prevailing sanitary conditions.

Tuberculosis is transmitted mainly by airborne droplets of sputum and saliva containing mycobacteria; the droplets are discharged when an infected person coughs, sneezes, or laughs. The bacteria are disseminated with these droplets to a distance of 0.5–1.5 m, remaining in the air about 30 to 60 minutes, and enter the lungs of nearby persons. Droplets of sputum may also remain on the clothing and underwear of an infected person, or on the floor, furniture, rugs, and walls. The droplets dry up, but the mycobacteria they contain are highly resistant to environmental factors and remain viable for a long time. When infected clothing is shaken, the surrounding air may become contaminated with minute particles of dried sputum if the room is not thoroughly cleaned.

Mycobacteria may also enter the body when a person drinks raw infected milk or eats incompletely cooked meat, as well as through a scratch on the skin, for example, when a dairymaid milks a cow with an infected udder. Important factors in all modes of infection are the duration of contact with the source of infection, and the number of bacilli entering the body—that is, the extent of the infection. If the contact is brief, tuberculosis is less likely to develop; it occurs far more often after prolonged, close contact with an infected person who discharges mycobacte-ria-containing sputum without following rules of personal hygiene. Drug-resistant mycobacteria develop in the body of an infected person after incorrect and irregular treatment with modern antituberculotic agents, and these mycobacteria may infect individuals who come in contact with him.

Tuberculosis results only rarely from infection. The great majority of infected persons do not develop the disease, owing to the activity of the body’s defense mechanisms. The body’s innate resistance to tuberculosis is reinforced by specific immunity acquired after vaccination with BCG or after recovery from a mild case of the disease. Factors favoring the development of tuberculosis include extensive and repeated infection, as well as low resistance caused by insufficient high-quality animal proteins and vitamins, in particular, vitamin C. Other contributing factors are unfavorable working conditions and occupational hazards, especially the inhaling of dust containing large amounts of suicide and fluorine. A person is more susceptible if he has had, or is presently suffering from, diabetes mellitus, chronic bronchitis, or alcoholism. Age is also an important factor: young children, who have insufficiently developed immunity mechanisms, are particularly susceptible, as are adolescents, whose nervous and endocrine systems are unstable during puberty. Also susceptible are the middle-aged and the elderly, who often suffer from functional impairment of various organs.

Tuberculosis is marked by the formation of single or multiple small tubercles or of larger foci and inflammatory areas, both at the site where the mycobacteria penetrate and in the organs and tissues to which the mycobacteria are conveyed by the blood and lymph or during inhalation. Under the influence of bacterial toxins, these tissue elements undergo caseous degeneration, and, owing to the influence of the enzymes formed by leukocytes, the tissue elements partially or completely liquefy. If the body’s resistance is adequate, the tubercles or foci are sometimes resorbed. A connective-tissue capsule that is separate from the surrounding tissue generally forms around the tubercles or foci, which may scar over completely and be deposited in caseous masses of calcium salts, sometimes with ossification of the focus. Under unfavorable conditions, caverns may form.

The mycobacteria pass from the cavern in the lungs through the bronchi to other areas of the lung tissue; if sputum is swallowed, they may be conveyed to the intestine. The mycobacteria may also penetrate the mucous membrane of the larynx and pharynx, where they help form new foci. Both the mycobacteria and other bacilli such as streptococci and staphylococci multiply in the cavern, aggravating the patient’s condition. Similar changes take place in other organs where mycobacteria find conditions favorable for reproduction and cause tuberculosis of the pleura, lymph nodes, eyes, bones, kidneys, and meninges. Generalized forms of the disease with simultaneous or successive involvement of many systems of the body are rare.

Tuberculosis is also marked by the rapid development of connective tissue in the lungs, liver, spleen, myocardium, and kidneys. Consequently, many patients die not of the underlying disease but of its complications or of concurrent diseases. However, even widespread and cavernous tuberculosis is curable if treated promptly and correctly. The tubercles, foci, and caverns in the lungs and other organs then undergo scarring, and the exúdate in the pleura, abdominal cavity, and meninges is resorbed.

Symptoms. The symptoms of tuberculosis are varied. Some appear soon after infection; this is the case with primary tuberculosis, whose course depends on the extent of the infection and of the individual’s resistance, and on age and living conditions. In children, the changes in the internal organs are sometimes so slight that they cannot be detected even by a thorough examination. The infection (tuberculosis intoxication) is manifested only by a positive skin reaction to tuberculin, followed by such symptoms as elevated body temperature, night sweats, insomnia, loss of appetite, fatigability, tearfulness, and irritability. This form of tuberculosis has become increasingly rare, and is now uncommon among adolescents and adults.

Symptoms of bronchadenitis, or involvement of the endotho-racic lymph nodes, generally occur after primary infection. The course of bronchadenitis is relatively benign since the foci formed in the lymph nodes are generally small. More severe forms of bronchadenitis develop in young children and are accompanied by a dry, hacking cough and sometimes by labored breathing. In primary infection, individual (and occasionally multiple) small tubercles or relatively large foci form in the lungs at the site where the mycobacteria entered, chiefly from the endothoracic lymph nodes. A primary tuberculosis complex is diagnosed from the presence of a single focus in a lung and the involvement of the endothoracic lymph nodes. The infection may spread from the lungs and lymph nodes to the pleura, resulting in tuberculous pleurisy, which is often the first clinical manifestation of tuberculosis.

Mycobacteria may also enter the cervical, axillary, subman-dibular, and inguinal lymph nodes, which then enlarge and become tender and immobile. The skin over the lymph nodes gradually becomes thin and inflamed. As the disease progresses, the lymph nodes liquefy, and the pus formed in them flows to the surface; over a lengthy period of time it is discharged through fistulas that scar over after healing. If the mycobacteria settle mainly in the lymph nodes of the abdominal cavity, the inflammation involves not only these nodes but the peritoneum (tuberculous peritonitis), the omentum, and the intestine. Symptoms include severe spasmodic abdominal pain, diarrhea alternating with constipation, distension of the intestine, poor appetite, and loss of weight. The infection may reach the bones and joints, causing symptoms of intoxication as well as local manifestations. Tuberculosis of the joints is marked by limited mobility and pain during movement. If the spine is affected, symptoms of spondylitis are also present.

In tuberculosis of the kidneys and bladder, urination is frequent and painful, and there are dull pains in the lumbus. If meningitis occurs, symptoms include severe persistent headaches, vomiting unrelated to food intake, convulsions, and unconsciousness. Timely treatment can prevent death, which was once inevitable, and result in a complete cure.

Tuberculosis of the skin is marked by the formation of tubercles and nodules, or of fairly large nodes and indurations in the subcutaneous tissue. These often appear on the extremities, face, chest, and buttocks, and sometimes ulcerate. Lupus vulgaris is a rare disfiguring form of tuberculosis. When tuberculosis affects the eyes, the symptoms are reddening and edema of the mucous membrane, and the formation of phlyctenae. Symptoms of tuberculosis of the vascular membrane of the eye are the formation of tubercles, photophobia, loss of visual acuity, and sometimes blindness.

The commonest form of tuberculosis is pulmonary tuberculosis, which results chiefly from reinfection of former foci and scars in the lungs and lymph nodes where the infection is dormant. When the body’s resistance is low, the mycobacteria begin to multiply rapidly and to release toxins, causing active tuberculosis. Pulmonary tuberculosis may also be caused by repeated infection, especially after close, prolonged contact with an infected person. Such secondary pulmonary tuberculosis generally begins with the formation of individual small foci, mainly in the upper lobes of the lungs (focal tuberculosis), or with fairly large inflammatory foci differing in shape and size (infiltrative tuberculosis). Disseminated tuberculosis, or acute miliary tuberculosis, in which the foci are disseminated throughout the lungs, is less common.

In pulmonary tuberculosis, symptoms are sometimes slow to manifest themselves, but most patients experience a lowered sense of well-being, night sweats, elevated body temperature, and loss of appetite and of capacity for work. The disease is often accompanied by a dry cough, and occasionally by the discharge of mucopurulent sputum that often contains mycobacteria. The symptoms are more pronounced when lung tissue decomposes and a cavern forms. This occurs in acute tuberculosis and in acute fibroid tuberculosis, in which there may be pulmonary hemorrhage or the expectoration of blood or of blood-stained sputum (hemoptysis). Mycobacteria are generally found in the sputum. The disease may be manifested by dry pleurisy or by pleurisy accompanied by an accumulation of exúdate in the pleural cavity.

Pulmonary tuberculosis is diagnosed mainly by photo-fluorography, a type of roentgenography that is used for testing large numbers of people. Photofluorography can detect tuberculosis when the disease is latent or when it resembles influenza, chronic bronchitis, or chronic pneumonia.

Pulmonary tuberculosis affects persons of all ages, particularly the elderly, and even persons over 90 years of age. Generally, however, the disease begins in youth or middle age and progresses slowly, sometimes for ten to 20 years or more, mainly because of delayed and inadequate treatment. Acute and severe forms that involve the larynx, intestine, and other organs are becoming increasingly rare, owing to a number of factors: improved living conditions, early detection, and highly effective methods of prevention and treatment.

Treatment. The use of isoniazid, streptomycin, and other anti-tuberculotics is an important element in the treatment of tuberculosis. By acting on the enzymes, proteins, and other biochemical constituents of mycobacteria, these drugs suppress the metabolism’and reproduction of the causative agent and decrease the amount of toxins discharged. Two or three antituberculotics are generally taken simultaneously for nine to 18 months or more, depending on the patient’s ability to tolerate the drugs and on the mycobacteria’s resistance to the drugs. The daily dose is often taken at one time; later, the drugs are taken two or three times a week. Vitamins B₁, B₆, and C, desensitizing agents, and cortico-steroid hormones are used to prevent or eliminate allergic, toxic, or metabolic side effects or their combinations.

Chemotherapy is combined with other methods of treatment to restore the body’s normal physiological state and increase its resistance to infection. It is imperative for the patient to stay in a sanatorium and make use of natural therapeutic factors. Of great importance are proper diet, rest or physical conditioning, and hardening, that is, development of the body’s resistance. A stay in a climatic health resort, for example, in the southern Crimea, is prescribed for some patients. Tuberculin is sometimes administered together with tuberculostatics. Artificial pneumothorax and other types of collapse therapy, widely used before antibacterial agents were known, are occasionally used.

When the patient cannot be cured by antituberculotics and other agents, the affected parts of the lungs are removed surgically. Surgery is also performed for tuberculosis of the bones, kidneys, and appendages of the sex organs. Chemotherapy is used in operative cases and is continued for a long time after the operation. Early treatment cures the great majority of patients with pulmonary tuberculosis. When the prescribed regimen is followed and tuberculostatics are taken regularly for 12 to 15 months, the discharge of bacteria ceases in 90 to 98 percent of the patients in whom pulmonary tuberculosis is detected at an early stage; caverns in the lungs heal in 80 to 90 percent of such patients. Many children, adolescents, and adults now recover from tuberculosis of the bones and kidneys and from meningitis. Consequently, mortality from tuberculosis has greatly declined.

Prevention. Tuberculosis is prevented by state-supported and community programs, including the construction of apartment buildings and public facilities, improved sanitation at places of work, environmental protection, and the raising of the population’s economic and cultural level. Resistance to tuberculosis is increased by such measures as physical culture, hardening, hiking, sports, and proper hygienic conditions for children in nurseries, children’s homes, and schools. To prevent infection within a family, family members with the disease should have separate rooms or live in separate apartments.

Other means of preventing tuberculosis include raising the educational level and increasing the observance of proper sanitation among the population, teaching patients to observe the rules of personal hygiene, hospitalizing infected persons, and removing infected persons from work in children’s institutions and enterprises involving contact with food. Veterinary measures include the disinfection of milk and other food products, and the isolation and slaughter of diseased cattle.

Vaccination with BCG is used for the specific prevention of tuberculosis. In the USSR, all newborns are vaccinated, and all persons are revaccinated up to the age of 30. A positive reaction to the Mantoux test indicates immunity, which lasts for three to five years and then gradually declines. If tuberculosis does not develop during this time, vaccination is repeated. Vaccination with BCG prevents the disease in almost 80 percent of cases and mitigates its course in the remaining-20 percent. Isoniazid, sometimes combined with para-aminosalicyclic acid, is administered daily, generally for a two- to three-month period twice a year, to children, adolescents, and adults in close contact with patients who discharge mycobacteria. These drugs are also administered to other high-risk individuals, including those exhibiting a positive reaction to the tuberculin test, a pronounced reaction to the Mantoux test, or nonactive tuberculous changes in the lungs.

The timely detection of tuberculosis is an important preventive measure. It is achieved by administering the tuberculin test to young children, as well as by testing children over 12 years of age by means of photofluorography at least once every two years, and yearly in Moscow and some other cities. All urban and rural dwellers should be examined regularly in this way. More frequent examinations (yearly or twice yearly) are advisable for hospital and clinical personnel, workers in children’s institutions, students and school personnel, transport workers, barbers and hairdressers, persons who handle food, industrial workers exposed to dust and harmful gases, and persons who come in contact with tuberculosis patients. Persons who have recovered from tuberculosis, but who have traces of latent forms of tuberculosis in their lungs, should be examined at least once a year.

Special working arrangements for individuals and groups help prevent exacerbations of tuberculosis and maintain the work capacity of affected persons. If patients cannot return to their former jobs and need to be requalified, they are taught new skills with the aid of all types of therapy in workshops organized in clinics and sanatoriums in many cities of the USSR. Special work sanatoriums also exist for agricultural workers. Some tuberculosis sanatoriums in the GDR, Poland, Hungary, Italy, the FRG, and other countries have been converted to work rehabilitation centers for pulmonary tuberculosis patients.

Efforts to control tuberculosis in the USSR involve the cooperation of public health, educational, and welfare agencies, trade unions, large industrial enterprises and kolkhozes, public health committees of councils of workers’ deputies, the Red Cross, and the Red Crescent. The most important control functions are carried out by specialized medical institutions and their clinics, and such subdivisions as hospitals, preventoria, and rehabilitation workshops. As of 1972, the USSR had more than 5,500 tuberculosis sanatoriums and divisions or consulting rooms in polyclinics, as well as 261,000 hospital beds. More than 23,500 specialists in tuberculosis and other diseases were employed in these medical facilities. Medical care of patients of all ages and with all forms of tuberculosis is free in the USSR.

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Lotte, A., and S. Perdrizet. “Morbidité par tuberculose en France et dans d’autres pays Européens, ” Bulletin de l’Institut national de la santé et de la recherche médicale, l’INSERM, 1971, vol. 26, no. 2, pp. 601–742.
Edwards, L., F. Acquaviva, and T. Livescay. “Identification of Tuberculosis Infected.” American Review of Respiratory Diseases, 1973, vol. 108, no. 6, pp. 1334–39.A. E. RABUKHINInanimals. More than 55 species of domestic and wild mammals and about 25 species of birds are susceptible to tuberculosis. Cattle, swine, and chickens are most susceptible; goats, dogs, ducks, and geese less susceptible; and horses, sheep, and cats least susceptible of all. The bovine variety of tuberculosis bacteria is pathogenetic for all mammals and to a lesser extent for birds. The human variety causes tuberculosis in horses, dogs, swine, cats, sheep, birds, and cattle. The avian variety affects birds, swine, horses, dogs, and sometimes cattle. Tuberculosis of animals is widespread in many countries, especially in Western Europe, where it causes substantial economic losses to livestock raising.
The source of the causative agent is infected animals that discharge bacteria together with feces, sputum, or milk, and occasionally with urine or sperm. The disease is transmitted in feed, water, manure, and litter and by grooming implements that have been contaminated by infected excretions. The causative agent survives for a long time in barnyards, poultry yards, ranges, pastures, and watering places. The animals become infected by inhaling the causative agent with airborne droplets or ingesting it with food, generally when they are confined in stalls or pens in congested conditions, improperly fed, and overworked.
Tuberculosis in animals is chronic but may be acute in young animals after extensive infection. The symptoms are highly varied and appear several months or even years after infection. In cattle, the symptoms of pulmonary tuberculosis include a cough and elevated body temperature; the symptoms in intestinal tuberculosis are diarrhea and the presence of mucus, pus, and blood in the feces. Involvement of the uterus and ovaries results in miscarriages and sterility. The lymph nodes typically become enlarged. As the disease develops, the animals lose their appetite and become emaciated; their eyes become sunken and their hair luster-less. Affected animals tire easily and become stooped.
Tuberculosis in swine is generally asymptomatic; if pronounced, the lymph nodes enlarge, a cough develops, and the animals become emaciated. Hens infected with tuberculosis are listless, become rapidly emaciated, and cease laying eggs. Tuberculosis in dogs affects the lungs, intestine, bones, and joints.
Tuberculosis in animals is diagnosed by means of clinical, pathological, allergy, and laboratory tests. Application of the tuberculin test is of major importance. The treatment of tuberculosis in animals is economically unjustified. The disease is prevented and controlled by protecting disease-free farms against the causative agent, examining animals regularly in order to detect the disease promptly, slaughtering diseased animals and segregating unaffected young animals, carrying out coordinated sanitary measures to eradicate the causative agent, and protecting humans from infection. The animals on all farms are examined and given the tuberculin test yearly in order to detect those with the disease. Farms on which tuberculosis is found are placed under quarantine. The diseased animals are slaughtered, and the remaining animals examined by means of the tuberculin test. The farms are then stocked with animals from disease-free farms. Milk from animals with a positive tuberculin reaction is disinfected by boiling and used on the same farm. Eggs from infected flocks are used mainly in the baking industry.

REFERENCE

Rotov, V. I., P. I. Kokurichev, and P. E. Savchenko. Tuberkulezsel’skokhoziaistvennykh zhivotnykh. Kiev, 1973.

Tuberculosis

any of several bacterial plant diseases characterized by the formation of rough protuberances, or tubercles, on the affected organs. Cavities filled with bacteria develop inside the tubercles; the bacteria are the causative agents of the disease. Tuberculosis attacks the sugar beet, olive, oleander, and ash.

The causative agent of the disease in sugar beets is Xantho-monas beticola. The growths form on the edible roots. The disease occurs in many countries where the sugar beet is a major crop. Usually only a few plants are affected, and, therefore, economic losses are minor. Control measures include proper crop rotation and destruction of diseased roots during harvesting.

In the olive the disease is caused by Pseudomonas savastanoi and is manifested by the formation of walnut-sized swellings on the branches, leaves, and roots. Diseased branches do not grow or bear fruit; sometimes the trees die. Epiphytotics are especially harmful in plant nurseries. The disease is spread by wind and rain, as well as by the olive fruit fly. It occurs mainly in Greece, Italy, and France. In the USSR the disease is an object of external quarantine. Control measures include obtaining healthy planting and grafting material and pruning and destroying diseased branches.

Tuberculosis of the oleander is caused by Pseudomonas savastanoi v. nerii. Galls form on the branches, leaves, and inflorescences. The disease is known in Italy, Spain, France, southern Africa, Australia, the USA, the USSR, and other countries. The causative agent of the disease in ash is Pseudomonas savastanoi v. fraxini. The knots develop on trunks and branches. The disease is observed in France, Italy, the Federal Republic of Germany, the German Democratic Republic, Great Britain, Australia, and the USSR. Control measures for tuberculosis of oleander and ash are the same as for tuberculosis of olive.

REFERENCES

Bakterial’nye bolezni rastenii, 2nd ed. Moscow, 1960.
Slovar’-spravochnik fitopatologa, 2nd ed. Edited by P. N. Golovin. Leningrad, 1967.
Zhuravlev, I. I., and D. V. Sokolov. Lesnaiafitopatologiia. Moscow, 1969.

N. P. IASHNOVA

tuberculosis

[tə‚bər·kyə′lō·səs] (medicine) A chronic infectious disease of humans and animals primarily involving the lungs caused by the tubercle bacillus, Mycobacterium tuberculosis, or by M. bovis. Also known as consumption; phthisis.

tuberculosis

a communicable disease caused by infection with the tubercle bacillus, most frequently affecting the lungs (pulmonary tuberculosis)

tuberculosis

Tuberculosis

Definition

Tuberculosis (TB) is a potentially fatal contagious disease that can affect almost any part of the body but is mainly an infection of the lungs. It is caused by a bacterial microorganism, the tubercle bacillus or Mycobacterium tuberculosis. Although TB can be treated, cured, and can be prevented if persons at risk take certain drugs, scientists have never come close to wiping it out. Few diseases have caused so much distressing illness for centuries and claimed so many lives.

Description

Overview

Tuberculosis was popularly known as consumption for a long time. Scientists know it as an infection caused by M. tuberculosis. In 1882, the microbiologist Robert Koch discovered the tubercle bacillus, at a time when one of every seven deaths in Europe was caused by TB. Because antibiotics were unknown, the only means of controlling the spread of infection was to isolate patients in private sanitoria or hospitals limited to patients with TB—a practice that continues to this day in many countries. The net effect of this pattern of treatment was to separate the study of tuberculosis from mainstream medicine. Entire organizations were set up to study not only the disease as it affected individual patients, but its impact on the society as a whole. At the turn of the twentieth century more than 80% of the population in the United States were infected before age 20, and tuberculosis was the single most common cause of death. By 1938 there were more than 700 TB hospitals in this country.Tuberculosis spread much more widely in Europe when the industrial revolution began in the late nineteenth century. The disease became widespread somewhat later in the United States, because the movement of the population to large cities made overcrowded housing so common. When streptomycin, the first antibiotic effective against M. tuberculosis, was discovered in the early 1940s, the infection began to come under control. Although other more effective anti-tuberculosis drugs were developed in the following decades, the number of cases of TB in the United States began to rise again in the mid-1980s. This upsurge was in part again a result of overcrowding and unsanitary conditions in the poor areas of large cities, prisons, and homeless shelters. Infected visitors and immigrants to the United Stateshave also contributed to the resurgence of TB. An additional factor is the AIDS epidemic. AIDS patients are much more likely to develop tuberculosis because of their weakened immune systems. There still are an estimated 8-10 million new cases of TB each year worldwide, causing roughly 3 million deaths.

High-risk populations

THE ELDERLY. Tuberculosis is more common in elderly persons. More than one-fourth of the nearly 23,000 cases of TB reported in the United States in 1995 developed in people above age 65. Many elderly patients developed the infection some years ago when the disease was more widespread. There are additional reasons for the vulnerability of older people: those living in nursing homes and similar facilities are in close contact with others who may be infected. The aging process itself may weaken the body's immune system, which is then less able to ward off the tubercle bacillus. Finally, bacteria that have lain dormant for some time in elderly persons may be reactivated and cause illness.RACIAL AND ETHNIC GROUPS. TB also is more common in blacks, who are more likely to live under conditions that promote infection. At the beginning of the new millennium, two-thirds of all cases of TB in the United States affect African Americans, Hispanics, Asians, and persons from the Pacific Islands. Another one-fourth of cases affect persons born outside the United States. As of 2002, the risk of TB is still increasing in all these groups.As of late 2002, TB is a major health problem in certain specific immigrant communities, such as the Vietnamese in southern California. One team of public health experts in North Carolina maintains that treatment for tuberculosis is the most pressing health care need of recent immigrants to the United States. In some cases, the vulnerability of immigrants to tuberculosis is increased by occupational exposure, as a recent outbreak of TB among Mexican poultry farm workers in Delaware indicates. Other public health experts are recommending tuberculosis screening at the primary care level of all new immigrants and refugees.LIFESTYLE FACTORS. The high risk of TB in AIDS patients extends to those infected by human immunodeficiency virus (HIV) who have not yet developed clinical signs of AIDS. Alcoholics and intravenous drug abusers are also at increased risk of contracting tuberculosis. Until the economic and social factors that influence the spread of tubercular infection are remedied, there is no real possibility of completely eliminating the disease.

Causes and symptoms

Transmission

Tuberculosis spreads by droplet infection. This type of transmission means that when a TB patient exhales, coughs, or sneezes, tiny droplets of fluid containing tubercle bacilli are released into the air. This mist, or aerosol as it is often called, can be taken into the nasal passages and lungs of a susceptible person nearby. Tuberculosis is not, however, highly contagious compared to some other infectious diseases. Only about one in three close contacts of a TB patient, and fewer than 15% of more remote contacts, are likely to become infected. As a rule, close, frequent, or prolonged contact is needed to spread the disease. Of course, if a severely infected patient emits huge numbers of bacilli, the chance of transmitting infection is much greater. Unlike many other infections, TB is not passed on by contact with a patient's clothing, bed linens, or dishes and cooking utensils. The most important exception is pregnancy. The fetus of an infected mother may contract TB by inhaling or swallowing the bacilli in the amniotic fluid.

Progression

Once inhaled, tubercle bacilli may reach the small breathing sacs in the lungs (the alveoli), where they are taken up by cells called macrophages. The bacilli multiply within these cells and then spread through the lymph vessels to nearby lymph nodes. Sometimes the bacilli move through blood vessels to distant organs. At this point they may either remain alive but inactive (quiescent), or they may cause active disease. Actual tissue damage is not caused directly by the tubercle bacillus, but by the reaction of the person's tissues to its presence. In a matter of weeks the host develops an immune response to the bacillus. Cells attack the bacilli, permit the initial damage to heal, and prevent future disease permanently.Infection does not always mean disease; in fact, it usually does not. At least nine of ten patients who harbor M. tuberculosis do not develop symptoms or physical evidence of active disease, and their x-rays remain negative. They are not contagious; however, they do form a pool of infected patients who may get sick at a later date and then pass on TB to others. It is thought that more than 90% of cases of active tuberculosis come from this pool. In the United States this group numbers 10-15 million persons. Whether or not a particular infected person will become ill is impossible to predict with certainty. An estimated 5% of infected persons get sick within 12-24 months of being infected. Another 5% heal initially but, after years or decades, develop active tuberculosis either in the lungs or elsewhere in the body. This form of the disease is called reactivation TB, or post-primary disease. On rare occasions a previously infected person gets sick again after a later exposure to the tubercle bacillus.

Pulmonary tuberculosis

Pulmonary tuberculosis is TB that affects the lungs. Its initial symptoms are easily confused with those of other diseases. An infected person may at first feel vaguely unwell or develop a cough blamed on smoking or a cold. A small amount of greenish or yellow sputum may be coughed up when the person gets up in the morning. In time, more sputum is produced that is streaked with blood. Persons with pulmonary TB do not run a high fever, but they often have a low-grade one. They may wake up in the night drenched with cold sweat when the fever breaks. The patient often loses interest in food and may lose weight. Chest pain is sometimes present. If the infection allows air to escape from the lungs into the chest cavity (pneumothorax) or if fluid collects in the pleural space (pleural effusion), the patient may have difficulty breathing. If a young adult develops a pleural effusion, the chance of tubercular infection being the cause is very high. The TB bacilli may travel from the lungs to lymph nodes in the sides and back of the neck. Infection in these areas can break through the skin and discharge pus. Before the development of effective antibiotics, many patients became chronically ill with increasingly severe lung symptoms. They lost a great deal of weight and developed a wasted appearance. This outcome is uncommon today—at least where modern treatment methods are available.

Extrapulmonary tuberculosis

Although the lungs are the major site of damage caused by tuberculosis, many other organs and tissues in the body may be affected. The usual progression is for the disease to spread from the lungs to locations outside the lungs (extrapulmonary sites). In some cases, however, the first sign of disease appears outside the lungs. The many tissues or organs that tuberculosis may affect include:

Bones. TB is particularly likely to attack the spine and the ends of the long bones. Children are especially prone to spinal tuberculosis. If not treated, the spinal segments (vertebrae) may collapse and cause paralysis in one or both legs.

Kidneys. Along with the bones, the kidneys are probably the commonest site of extrapulmonary TB. There may, however, be few symptoms even though part of a kidney is destroyed. TB may spread to the bladder. In men, it may spread to the prostate gland and nearby structures.
Female reproductive organs. The ovaries in women may be infected; TB can spread from them to the peritoneum, which is the membrane lining the abdominal cavity.
Abdominal cavity. Tuberculous peritonitis may cause pain ranging from the vague discomfort of stomach cramps to intense pain that may mimic the symptoms of appendicitis.
Joints. Tubercular infection of joints causes a form of arthritis that most often affects the hips and knees. The wrist, hand, and elbow joints also may become painful and inflamed.
Meninges. The meninges are tissues that cover the brain and the spinal cord. Infection of the meninges by the TB bacillus causes tuberculous meningitis, a condition that is most common in young children but is especially dangerous in the elderly. Patients develop headaches, become drowsy, and eventually comatose. Permanent brain damage is the rule unless prompt treatment is given. Some patients with tuberculous meningitis develop a tumor-like brain mass called a tuberculoma that can cause stroke-like symptoms.
Skin, intestines, adrenal glands, and blood vessels. All these parts of the body can be infected by M. tuberculosis. Infection of the wall of the body's main artery (the aorta), can cause it to rupture with catastrophic results. Tuberculous pericarditis occurs when the membrane surrounding the heart (the pericardium) is infected and fills up with fluid that interferes with the heart's ability to pump blood.
Miliary tuberculosis. Miliary TB is a life-threatening condition that occurs when large numbers of tubercle bacilli spread throughout the body. Huge numbers of tiny tubercular lesions develop that cause marked weakness and weight loss, severe anemia, and gradual wasting of the body.

Diseases similar to tuberculosis

There are many forms of mycobacteria other than M. tuberculosis, the tubercle bacillus. Some cause infections that may closely resemble tuberculosis, but they usually do so only when an infected person's immune system is defective. People who are HIV-positive are a prime example. The most common mycobacteria that infect AIDS patients are a group known as Mycobacterium avium complex (MAC). People infected by MAC are not contagious, but they may develop a serious lung infection that is highly resistant to antibiotics. MAC infections typically start with the patient coughing up mucus. The infection progresses slowly, but eventually blood is brought up and the patient has trouble breathing. In AIDS patients, MAC disease can spread throughout the body, with anemia, diarrhea, and stomach pain as common features. Often these patients die unless their immune system can be strengthened. Other mycobacteria grow in swimming pools and may cause skin infection. Some of them infect wounds and artificial body parts such as a breast implant or mechanical heart valve.

Diagnosis

The diagnosis of TB is made on the basis of laboratory test results. The standard test for tuberculosis—which is the so-called tuberculin skin test—detects the presence of infection, not of active TB. Tuberculin is an extract prepared from cultures of M. tuberculosis. It contains substances belonging to the bacillus (antigens) to which an infected person has been sensitized. When tuberculin is injected into the skin of an infected person, the area around the injection becomes hard, swollen, and red within one to three days. Today skin tests utilize a substance called purified protein derivative (PPD) that has a standard chemical composition and is therefore is a good measure of the presence of tubercular infection. The PPD test is also called the Mantoux test. The Mantoux PPD skin test is not, however, 100% accurate; it can produce false positive as well as false negative results. What these terms mean is that some people who have a skin reaction are not infected (false positive) and that some who do not react are in fact infected (false negative). The PPD test is, however, useful as a screener. Anyone who has suspicious findings on a chest x ray, or any condition that makes TB more likely should have a PPD test. In addition, those in close contact with a TB patient and persons who come from a country where TB is common also should be tested, as should all healthcare personnel and those living in crowded conditions or institutions.Because the symptoms of TB cover a wide range of severity and affected body parts, diagnosis on the basis of external symptoms is not always possible. Often, the first indication of TB is an abnormal chest x-ray or other test result rather than physical discomfort. On a chest x ray, evidence of the disease appears as numerous white, irregular areas against a dark background, or as enlarged lymph nodes. The upper parts of the lungs are most often affected. A PPD test is always done to show whether the patient has been infected by the tubercle bacillus. To verify the test results, the physician obtains a sample of sputum or a tissue sample (biopsy) for culture. Three to five sputum samples should be taken early in the morning. If necessary, sputum for culture can be produced by spraying salt solution into the windpipe. Culturing M. tuberculosis is useful for diagnosis because the bacillus has certain distinctive characteristics. Unlike many other types of bacteria, mycobacteria can retain certain dyes even when exposed to acid. This so-called acid-fast property is characteristic of the tubercle bacillus.Body fluids other than sputum can be used for culture. If TB has invaded the brain or spinal cord, culturing a sample of spinal fluid will make the diagnosis. If TB of the kidneys is suspected because of pus or blood in the urine, culture of the urine may reveal tubercular infection. Infection of the ovaries in women can be detected by placing a tube having a light on its end (a laparoscope) into the area. Samples also may be taken from the liver or bone marrow to detect the tubercle bacillus.One important new advance in the diagnosis of TB is the use of molecular techniques to speed the diagnostic process as well as improve its accuracy. As of late 2005, four molecular techniques are increasingly used in laboratories around the world. They include polymerase chain reaction to detect mycobacterial DNA in patient specimens; nucleic acid probes to identify mycobacteria in culture; restriction fragment length polymorphism analysis to compare different strains of TB for epidemiological studies; and genetic-based susceptibility testing to identify drugresistant strains of mycobacteria.

Treatment

Supportive care

In the past, treatment of TB was primarily supportive. Patients were kept in isolation, encouraged to rest, and fed well. If these measures failed the lung was collapsed surgically so that it could "rest" and heal. Today surgical procedures still are used when necessary, but contemporary medicine relies on drug therapy as the mainstay of home care. Given an effective combination of drugs, patients with TB can be treated at home as well as in a sanitorium. Treatment at home does not pose the risk of infecting other household members.

Drug therapy

Most patients with TB can recover if given appropriate medication for a sufficient length of time. Three principles govern modern drug treatment of TB:

Lowering the number of bacilli as quickly as possible. This measure minimizes the risk of transmitting the disease. When sputum cultures become negative, this has been achieved. Conversely, if the sputum remains positive afterfive to six months, treatment has failed.
Preventing the development of drug resistance. For this reason, at least two different drugs and sometimes three are always given at first. If drug resistance is suspected, at least two different drugs should be tried.
Long-term treatment to prevent relapse.

Five drugs are most commonly used today to treat tuberculosis: isoniazid (INH, Laniazid, Nydrazid); rifampin (Rifadin, Rimactane); pyrazinamide (Tebrazid); streptomycin; and ethambutol (Myambutol). The first three drugs may be given in the same capsule to minimize the number of pills in the dosage. As of 1998, many patients are given INH and rifampin together for six months, with pyrazinamide added for the first two months. Hospitalization is rarely necessary because many patients are no longer infectious after about two weeks of combination treatment. Follow-up involves monitoring of side effects and monthly sputum tests. Of the five medications, INH is the most frequently used drug for both treatment and prevention.

Surgery

Surgical treatment of TB may be used if medications are ineffective. There are three surgical treatments for pulmonary TB: pneumothorax, in which air is introduced into the chest to collapse the lung; thoracoplasty, in which one or more ribs are removed; and removal of a diseased lung, in whole or in part. It is possible for patients to survive with one healthy lung. Spinal TB may result in a severe deformity that can be corrected surgically.

Prognosis

The prognosis for recovery from TB is good for most patients, if the disease is diagnosed early and given prompt treatment with appropriate medications on a long-term regimen. According to a 2002 Johns Hopkins study, most patients in the United States who die of TB are older—average age 62—and suffer from such underlying diseases as diabetes and kidney failure.Modern surgical methods have a good outcome in most cases in which they are needed. Miliary tuberculosis is still fatal in many cases but is rarely seen today in developed countries. Even in cases in which the bacillus proves resistant to all of the commonly used medications for TB, other seldom-used drugs may be tried because the tubercle bacilli have not yet developed resistance to them.

Prevention

General measures

General measures such as avoidance of overcrowded and unsanitary conditions are also necessary aspects of prevention. Hospital emergency rooms and similar locations can be treated with ultraviolet light, which has an antibacterial effect.

Vaccination

Vaccination is one major preventive measure against TB. A vaccine called BCG (Bacillus Calmette-Guérin, named after its French developers) is made from a weakened mycobacterium that infects cattle. Vaccination with BCG does not prevent infection by M. tuberculosis but it does strengthen the immune system of first-time TB patients. As a result, serious complications are less likely to develop. BCG is used more widely in developing countries than in the United States. The effectiveness of vaccination is still being studied; it is not clear whether the vaccine's effectiveness depends on the population in which it is used or on variations in its formulation.

Prophylactic use of isoniazid

INH can be given for the prevention as well as the treatment of TB. INH is effective when given daily over a period of six to 12 months to people in high-risk categories. INH appears to be most beneficial to persons under the age of 25. Because INH carries the risk of side-effects (liver inflammation, nerve damage, changes in mood and behavior), it is important to give it only to persons at special risk.High-risk groups for whom isoniazid prevention may be justified include:

close contacts of TB patients, including health care workers
newly infected patients whose skin test has turned positive in the past two years
anyone who is HIV-positive with a positive PPD skin test; Isoniazid may be given even if the PPD results are negative if there is a risk of exposure to active tuberculosis
intravenous drug users, even if they are negative for HIV
persons with positive PPD results and evidence of old disease on the chest x-ray who have never been treated for TB
patients who have an illness or are taking a drug that can suppress the immune system
persons with positive PPD results who have had intestinal surgery; have diabetes or chronic kidney failure; have any type of cancer; or are more than 10% below their ideal body weight

people from countries with high rates of TB who have positive PPD results
people from low-income groups with positive skin test results
persons with a positive PPD reaction who belong to high-risk ethnic groups (African Americans, Hispanics, Native Americans, Asians, and Pacific Islanders)

Resources

Books

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Infectious Diseases Caused by Mycobacteria." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.Pelletier, Kenneth R., MD. The Best Alternative Medicine, Part II, "CAM Therapies for Specific Conditions: Tuberculosis." New York: Simon & Schuster, 2002.

Periodicals

"Changing Patterns of New Tuberculosis Infections." Infectious Disease Alert August 15, 2002: 171-172."'Drug of Dreams' Preps for First Large-Scale Trail: Study to Begin this Year; Moxifloxacin to Debut Soon in Study 27." TB Monitor July 2002: 73.Efferen, Linda S. "Tuberculosis: Practical Solutions to Meet the Challenge." Journal of Respiratory Diseases November 1999: 772.Fielder, J. F., C. P. Chaulk, M. Dalvi, et al. "A High Tuberculosis Case-Fatality Rate in a Setting of Effective Tuberculosis Control: Implications for Acceptable Treatment Success Rates." International Journal of Tuberculosis and Lung Disease 6 (December 2002): 1114-1117."Guidelines Roll Out Two New Variations: Experts give Both a Thumbs Up." TB Monitor August 2002: 85.Houston, H. R., N. Harada, and T. Makinodan. "Development of a Culturally Sensitive Educational Intervention Program to Reduce the High Incidence of Tuberculosis Among Foreign-Born Vietnamese." Ethnic Health 7 (November 2002): 255-265.Kim, D. Y., R. Ridzon, B. Giles, and T. Mireles. "Pseudo-Outbreak of Tuberculosis in Poultry Plant Workers, Sussex County, Delaware." Journal of Occupational and Environmental Medicine 44 (December 2002): 1169-1172.Moua, M., F. A. Guerra, J. D. Moore, and R. O. Valdiserri. "Immigrant Health: Legal Tools/Legal Barriers." Journal of Law and Medical Ethics 30, Supplement 3 (Fall 2002): 189-196."New Drugs Sought for Top Killer of Young Women Worldwide." Women's Health Weekly July 25, 2002: 20."Poor Patient Compliance Key to Drug Resistance in Tuberculosis." Pulse July 1, 2002: 18.Stauffer, W. M., D. Kamat, and P. F. Walker. "Screening of International Immigrants, Refugees, and Adoptees." Primary Care 29 (December 2002): 879-905.Su, W. J. "Recent Advances in the Molecular Diagnosis of Tuberculosis." Journal of Microbiology, Immunology, and Infection 35 (December 2002): 209-214.

Organizations

American Lung Association. 1740 Broadway, New York, NY 10019. (800) 586-4872. http://www.lungusa.org.National Heart, Lung, and Blood Institute (NHLBI). P. O. Box 30105, Bethesda, MD 20824-0105. (301) 592-8573. www.nhlbi.nih.gov.

Other

New York State Department of Health. "Communicable Disease Fact Sheet."

tuberculosis

[too-ber´ku-lo´sis] an infectious, inflammatory, reportable disease that is chronic in nature and usually affects the lungs (pulmonary tuberculosis), although it may occur in almost any part of the body. The causative agent is Mycobacterium tuberculosis (also known as the tubercle bacillus). Formerly, the only other species of Mycobacterium thought to be pathogenic to humans were M. bovis and M. avium. It is now known that other species can produce diseases similar to true tuberculosis, including M. intracellulare, M. kansasii, M. simiae, and M. szulgai.
The most common mode of transmission of tuberculosis in the United States is inhalation of infected droplet nuclei. In some other parts of the world bovine tuberculosis, which is carried by unpasteurized milk and other dairy products from tuberculous cattle, is more prevalent. A rare mode of transmission is by infected urine, especially for young children using the same toilet facilities. Tuberculosis is also seen as an opportunistic infection in virus" >human immunodeficiency virus (HIV) infection.
The tubercle bacillus is capable of surviving for months in dried sputum that is not exposed to sunlight. Within the body it can lie dormant for decades and then become reactivated years after an initial infection. This secondary tuberculosis infection (endogenous reinfection) can occur at any time the patient's resistance is lowered. For this reason, periodic evaluation for evidence of the disease is extremely important for anyone who has had a primary tuberculosis infection. The tubercle bacillus is destroyed by boiling for 5 minutes, by autoclaving, by contact with coal tar preparations, e.g., phenol, and by ultraviolet radiation.Primary and Secondary Tuberculosis. The first or primary infection with tuberculosis bacilli usually presents no symptoms. In about 99 per cent of those who are infected, the disease remains quiescent after the development of a hypersensitivity to the tuberculin microorganism and is no longer clinically significant.

The primary infection usually involves the middle or lower lung area. The primary lesion consists of a small area of exudation in the lung parenchyma (Ghon focus) which quickly becomes caseous (cheeselike) and spreads to the bronchopulmonary lymph nodes, where it gains access to the blood stream. Thus the stage is set for the development of a chronic pulmonary and extrapulmonary tuberculosis at a later time. In most instances, however, a secondary reinfection from inside the body (endogenous) or outside the body (exogenous) does not occur because of the subsequent development of tuberculin hypersensitivity and cellular immunity. The presence of antigen concentrations at the initial site of infection brings about necrosis and eventually fibrosis and calcification of the tissues, which arrests the infection and renders the disease inactive. If, however, the infection is not controlled, the patient develops the symptoms of progressive primary tuberculosis.
Secondary tuberculosis develops as a result of either endogenous or exogenous reinfection by the tubercle bacillus. This is the most common form of clinical tuberculosis. In the United States development of secondary tuberculosis is almost always the result of an endogenous reinfection, which occurs when the primary lesion becomes active. This most frequently happens in debilitated persons who have lowered resistance to disease.
Resistance to tuberculosis depends on the general health and living conditions of the individual. Poor health, crowded and unsanitary housing, malnutrition, and other illnesses can lower the body's defenses. A second factor that can lead to activation of the disease is frequent exposure to the bacilli or exposure to such numbers that even a healthy person cannot escape infection.Tuberculin Testing. The most commonly used test is the mantoux test, which consists of an intradermal injection of a purified protein derivative of tuberculin. An indurated area (wheal) of 8 to 10 mm in diameter 48 to 72 hours after injection is considered positive. Induration must be present; a reddened area is not indicative of a positive reaction. If the test is positive for tuberculin sensitivity, further studies, including x-rays, are indicated before a definite diagnosis of tuberculosis is established. False negative results can occur with acute viral infections and some neoplastic diseases, e.g., Hodgkin's disease.Culture of M. tuberculosis from sputum or some other body fluid is the only way to positively confirm tuberculosis.Symptoms. A child or young person with active tuberculosis usually suffers from one or more of the following symptoms: loss of energy, poor appetite, loss of weight, and fever. Even though these symptoms may have causes other than tuberculosis, they must be regarded as warning signals. In adults, listlessness and vague pains in the chest may go unnoticed, since they are often not severe enough to attract attention. Unfortunately, the symptoms that most people associate with tuberculosis (cough, expectoration of purulent sputum, fever, night sweats, and hemorrhage from the lungs) do not appear in the early, most easily curable stage of the disease; often their appearance is delayed until a year or more after the initial exposure to the bacilli.

Chronic pulmonary tuberculosis is often accompanied by pleurisy. Pleurisy with effusion often is the first symptom of tuberculosis. In certain cases, complications are possible and each has its characteristic symptoms. At a fairly late stage, the tuberculosis bacillus may cause ulcers or inflammation around the larynx (tuberculous laryngitis). Less often, tuberculous ulcers form on the tongue or tonsils. Sometimes intestinal infections develop; they are probably caused by swallowed bacteria-contaminated sputum. A most serious complication is the sudden collapse of a lung, the indication that a deep tuberculous cavity in the lung has perforated, or opened into the pleural cavity, allowing air and infected material to flow into it.
When a fairly large and previously walled-off lesion, or infected area, suddenly discharges its contents into the bronchial tree, the result is the infection of a large part of the lung, an acute and dangerous complication which causes tuberculous pneumonia.
Tuberculosis bacilli can spread to other parts of the body by way of the blood, producing miliary tuberculosis. When a large number of bacilli suddenly enter the circulatory system, they are carried to all areas of the body and may lodge in any organ. Minute tubercles form in the tissues of the organs affected; these lesions are about the size of a pinhead or millet seed (hence the name miliary). Unless promptly treated, and occasionally even then, the tiny lesions spread, join, and produce larger areas of infection.
Tuberculous pneumonia can begin in this way, as can tuberculosis of any other organ. Miliary infections involving the meninges produce a particularly serious disease; indeed, until the development of antibiotics, this condition nearly always proved fatal.
Practically all parts and organs of the body can be secondarily invaded by tubercle bacilli, a common type being involvement of the kidneys, which often spreads to the bladder and genitalia. Bone involvement, particularly of the spine (pott's disease), was once common, especially among children.
Lupus vulgaris, or tuberculosis of the skin, is characterized by brown nodules on the corium; another form of tuberculosis of the skin is tuberculosis indurativa, a chronic disease in which indurated nodules form on the skin. When the adrenal glands are affected by tuberculosis, a rare occurrence, the condition can cause addison's disease.Treatment and Care. Most persons with tuberculosis are cared for at home under the supervision of a public health nurse who periodically visits the patient and family. Hospitalization may be required for those patients who experience complications or who are noncompliant with chemotherapy. The importance of compliance with the entire course of chemotherapy should be stressed. Failure to complete chemotherapy is a major factor in the appearance of drug resistant tuberculosis.

Masks may be necessary for those having intimate contact with a patient who is just beginning chemotherapy, and in caring for patients who cannot or will not take precautions against spreading the infection. Usually, two to four weeks after medications are begun restrictions are removed regarding activities and contacts. Handwashing is essential to prevention of cross-infection. Fomites are not considered important in the transmission of tuberculosis and so no special precautions are required for eating utensils and other inanimate articles in the patient's room. Screening of family members and other contacts should be done. Standard precautions are used for patients with extrapulmonary tuberculosis and those who have a positive skin test even without evidence of disease. Institutionalized patients with pulmonary or laryngeal disease should be kept on airborne precautions. The Centers for Disease Control and Prevention has published "Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health Care Facilities." The document can be read on their web site at http://www.cdc.gov.Drugs. Isoniazid remains the major antituberculous agent. It is usually administered in combination with rifampin. Ethambutol is added if the patient comes from an area of high resistance. In isoniazid-resistant cases, rifampin is substituted as a companion drug for ethambutol. Other medications are used if resistant organisms have developed.Prevention. The incidence of tuberculosis is rising, and the development of resistant organisms is also rising. It must be stressed that medications must be taken as ordered. The best precautions are (1) maintenance of good health, (2) avoidance of unnecessary exposure to tuberculosis organisms, and (3) detection of the disease in its earliest stages.

Tuberculosis. The Ghon complex, typical of pulmonary tuberculosis, consists of a parenchymal focus and hilar lymph node lesions. The detailed section of the diagram shows typical features of tuberculous granuloma: central caseous necrosis surrounded by epithelioid cells, multinucleated giant cells, and lymphocytes. From Damjanov, 2000.avian tuberculosis a form affecting various birds, due to Mycobacterium avium, which may be communicated to humans and other animals. Individuals with impaired immunity have particular susceptibility to this infection.bovine tuberculosis an infection of cattle caused by Mycobacterium bovis, transmissible to humans and other animals.hematogenous tuberculosis that carried through the blood stream from the primary site of infection to other organs.miliary tuberculosis an acute form of tuberculosis in which minute tubercles are formed in a number of organs of the body, owing to dissemination of the bacilli throughout the body by the bloodstream.open tuberculosis 1. that in which there are lesions from which tubercle bacilli are being discharged out of the body.2. tuberculosis of the lungs with cavitation.pulmonary tuberculosis infection of the lungs by Mycobacterium tuberculosis; the first infection is usually quiescent, and it may develop later into tuberculous pneumonia and other conditions. See tuberculosis.renal tuberculosis disease of the kidney due to Mycobacterium tuberculosis, usually from bacillemia in cases of tuberculosis" >pulmonary tuberculosis. Pathological changes include granulomatous inflammation and caseous necrosis of kidney tissue. Called also nephrotuberculosis.tuberculosis verruco´sa cu´tis (warty tuberculosis) a condition usually resulting from external inoculation of the tubercle bacilli into the skin, with wartlike papules that coalesce to form patches with a reddened inflammatory border.

tu·ber·cu·lo·sis (TB),

(tū-ber'kyū-lō'sis), A specific disease caused by infection with Mycobacterium tuberculosis, the tubercle bacillus, which can affect almost any tissue or organ of the body, the most common site of the disease being the lungs. Primary TB is typically a mild or asymptomatic local pulmonary infection. Regional lymph nodes may become involved, but in otherwise healthy people generalized disease does not immediately develop. A cell-mediated immune response arrests the spread of organisms and walls off the zone of infection. Infected tissues and lymph nodes may eventually calcify. The tuberculin skin test result becomes positive within a few weeks and remains positive throughout life. Organisms in a primary lesion remain viable and can become reactivated months or years later to initiate secondary TB. Progression to the secondary stage eventually occurs in 10-15% of people who have had primary TB; in one half of these, progression occurs within 2 years. The risk of reactivation is increased by diabetes mellitus, malnutrition, HIV infection, silicosis, and various systemic or malignant conditions, as well as in patients with alcoholism, IV drug abusers, nursing home residents, and those receiving adrenocortical steroid or immunosuppressive therapy. Secondary or reactivation TB usually results in a chronic, spreading lung infection, most often involving the upper lobes. Minute granulomas (tubercles), just visible to the naked eye, develop in involved lung tissue, each consisting of a zone of caseation necrosis surrounded by chronic inflammatory cells (epithelioid histiocytes and giant cells). These lesions, which give the disease its name, are also found in other tissues (lymph nodes, bowel, kidney, skin) to which the disease may spread. Rarely, reactivation results in widespread dissemination of tubercles throughout the body (miliary TB). The symptoms of active pulmonary TB are fatigue, anorexia, weight loss, low-grade fever, night sweats, chronic cough, and hemoptysis. Local symptoms depend on the parts affected. Active pulmonary TB is relentlessly chronic and, if untreated, leads to progressive destruction of lung tissue. Cavities form in the lungs, and erosion into pulmonary blood vessels can result in life-threatening hemorrhage. Gradual deterioration of nutritional status and general health culminates in death due to wasting, infection, or multiple organ failure. Variant syndromes (tuberculous lymphadenitis in children, severe systemic disease in persons with AIDS) are caused by organisms of the Mycobacterium avium-intracellulare complex (MAIC). The diagnosis of TB is based on tuberculin skin testing (negative in 20% of people with active TB), imaging studies (computed tomography is more sensitive than standard chest radiography in detecting pleural effusion, miliary disease, and cavitation), and the finding of the causative organism in sputum or tissue specimens by acid-fast or fluorochrome staining, nucleic acid amplificatin, or culture. [tuberculo- + G. -osis, condition]

In 1993 the World Health Organization (WHO) declared TB a global emergency. Fully one third of the world's population is infected with TB. On a global scale, TB ranks first among infectious diseases as a cause of death. Two thirds of all the world's cases are in Asia, but the disease is also endemic in parts of Africa (where the highest incidence rates per capita are found) and eastern Europe. War and social upheaval have played a role in the spread of tuberculosis beyond endemic zones. Prevalence of infection is higher among refugees and immigrants. One third of all people with tuberculosis in the U.S. were born outside this country, and more than 50% of newly diagnosed cases occur in people of foreign birth. From the 1950s, when antibiotics began to be used for the treatment of TB, until the 1980s, the incidence and mortality of the disease declined steadily in the U.S. During the 1980s the incidence began to rise because of many new cases in people with AIDS and because of increasing prevalence of multidrug-resistant strains of M. tuberculosis. Since 1993 the figures have again declined, chiefly because of improvements in TB prevention and control programs in state and local health departments as a result of increased federal funding provided to states. At least one third of people with AIDS contract TB, and TB is the cause of death in one third of people who die of AIDS. Because antibiotic resistance in M. tuberculosis has been a growing problem for years, multidrug regimens, usually including isoniazid, rifampin, and pyrazinamide, are standard. Other drugs, such as ethambutol, streptomycin, kanamycin, and capreomycin, may be added or substituted. The success of treatment is limited not only by the resistance of organisms to several agents but also by the risk of severe toxic effects with all standard agents. Unlike most infections treated with antibiotics, TB requires not merely days or weeks of treatment but rather months and years. Long-term compliance with treatment regimens tends to be poor among mobile, indigent, and uneducated people. According to WHO, the principal reason for the spread of multidrug-resistant strains of M. tuberculosis is ineffectual management of TB control programs, particularly in developing countries. An inappropriate or unfinished course of chemotherapy not only leaves the patient still sick and still contagious, but favors the selection of resistant bacteria. It is estimated that 50 million of the world's cases of TB involve multiply resistant tubercle bacilli. The prevalence of infection due to drug-resistant strains is particularly high in some former Soviet states. Currently WHO urges that TB programs worldwide adopt the practice of directly observed therapy (DOT), in which a health care worker observes each patient swallowing each dose of medicine. In a study performed at several U.S. centers, DOT for TB was found to be cost effective when the cost of relapses and treatment failures was added to the cost of self-administered therapy, even though the raw cost of DOT was higher. U.S. public health authorities have established as a national goal the elimination of TB (defined as an incidence of less than 1 case per 1 million population) by 2010.

tuberculosis

(to͝o-bûr′kyə-lō′sĭs, tyo͝o-)n. Abbr. TB1. An infectious disease of humans and animals caused by the tubercle bacillus and characterized by the formation of tubercles on the lungs and other tissues of the body, often developing long after the initial infection.2. Tuberculosis of the lungs, characterized by the coughing up of mucus and sputum, fever, weight loss, and chest pain.

Medical history Infection by Mycobacterium tuberculosis, the ‘robber of youth’
Substance abuse A popular term for the epidemic of cocaine abuse

tuberculosis

Infectious disease A disease first known to the ancients; there are one million new cases of Mycobacterium tuberculosis/yr worldwide, of which ±10% of those in developing nations eventually die; 'smear'-positive cases in Africa–165/105, are more often clinically inactive than those in Asia where the rate is 110/105 US incidence: 9.3 cases/105–white/Hispanic 5.7/105, black 26.7/105, Asian 49.6/105; the previous trend of ↓ TB in the US reversed itself in the mid-1980s, due to ↑ of M tuberculosis and M avium complex in AIDS; up to 10 million in the US have latent TB–many of whom are poor, aged, malnourished; homeless or IVDAs Clinical Coughing, chest pain, hemoptysis, weight loss, fatigue, malaise, fever, night sweats Diagnosis Ziehl-Neelsen or Kinyoun AFB stains, viewed by LM; auramine-rhodamine stain with fluorescent microscopy; NAP test, nucleic acid probes, PCR Treatment-1º drugs Isoniazid, ethambutol, rifampicin, streptomycin 2º drugs Ethionamide, capreomycin, kanamycin, cycloserine, pyrazinamide, para-aminosalicylic acid. See Latent tuberculosis, MOTT, Mycobacterial infection, Multidrug resistant tuberculosis, Runyon classification. Cf Pseudotuberculosis.

tu·ber·cu·lo·sis

(TB) (tū-bĕr'kyū-lō'sis) A specific disease caused by Mycobacterium tuberculosis, which may affect almost any tissue or organ of the body, with the most common seat of the disease being the lungs; the anatomic lesion is the tubercle, which can undergo caseation necrosis; general symptoms are those of sepsis: hectic fever, sweats, and emaciation; often progressive, with high mortality if not treated. People with compromised immune systems, including those with AIDS, are at increased risk of severe infection. A high incidence also exists among injecting drug abusers. [tuberculo- + G. -osis, condition]

tuberculosis

(too-ber?kyu-lo'sis, tu-) [ tubercle + -osis],

TB

TUBERCULOSIS: anteroposterior x-ray of a patient diagnosed with advanced bilateral pulmonary tuberculosis (SOURCE: Centers for Disease Control and Prevention)

TUBERCULOSIS: Reported tuberculosis cases in the United States, 1982–2010 (adapted from Centers for Disease Control and Prevention)An infectious disease caused by the tubercle bacillus, Mycobacterium tuberculosis, and characterized pathologically by inflammatory infiltration, formation of tubercles, caseation, necrosis, abscesses, fibrosis, and calcification. It most commonly affects the respiratory system, but other parts of the body such as the gastrointestinal and genitourinary tracts, bones, joints, nervous system, lymph nodes, and skin may also become infected. Fish, amphibians, birds, and mammals (esp. cattle) are subject to the disease. Three types of the tubercle bacillus exist: human, bovine, and avian. Humans may become infected by any of the three types, but in the U.S. the human type predominates. Infection usually is acquired from contact with an infected person or an infected cow or through drinking contaminated milk. In the U.S., about 10 to 15 million persons have been infected with tuberculosis. In 2005 about 14,000 active cases were reported. In 2009, 11,545 new cases were reported in the U.S. Worldwide, about 2 billion people harbor the infection; about 9 million have active disease, and an estimated 2 million die from TB each year. The percentage of drug-resistant TB cases varies internationally.

Tuberculosis usually affects the lungs, but the disease may spread to other organs, including the gastrointestinal and genitourinary tracts, bones, joints, nervous system, lymph nodes, and skin. Macrophages surround the bacilli in an attempt to engulf them but cannot, producing granulomas with a soft, cheesy (caseous) core. From this state, lesions may heal by fibrosis and calcification and the disease may exist in an arrested or inactive stage. Depending on the person’s immune status and other factors, the disease may become reactivated as pulmonary TB or disseminated infection. Reactivation or exacerbation of the disease or reinfection gives rise to the chronic progressive form.

The incidence of TB declined steadily from the 1950s to about 1990, when the acquired immunodeficiency syndrome (AIDS) epidemic, an increase in the homeless population, an increase in immigrants from endemic areas, and a decrease in public surveillance caused a resurgence of the disease. Populations at greatest risk for TB include patients with human immunodeficiency virus (HIV), Asian and other refugees, the urban homeless, alcoholics and other substance abusers, persons incarcerated in prisons and psychiatric facilities, nursing home residents, patients taking immunosuppressive drugs, and people with chronic respiratory disorders, diabetes mellitus, renal failure, or malnutrition. People from these risk groups should be assessed for TB if they develop pneumonia; all health care workers should be tested annually.

Currently the only vaccine available to prevent tuberculosis is the BCG vaccine. It has somewhat limited effectiveness but is used in regions of the world where TB is endemic. illustration; immunological therapy; tuberculin skin test; vaccine, BCG;

Incubation Period

Approx. 4 to 12 weeks elapse between the time of infection and the time a demonstrable primary lesion or positive tuberculin skin test (TST) occurs.

Symptoms

Pulmonary TB produces chronic cough, sputum, fevers, sweats, and weight loss. TB may also cause neurological disease (meningitis), bone infections, urinary bleeding, and other symptoms if it spreads to other organs. TB is a major cause of infertility around the world.

Diagnosis

Tests used to diagnose latent infection with tuberculosis include a positive tuberculin skin test (TST) or a blood assay. A presumptive diagnosis of active disease is made by finding acid-fast bacilli in stained smears from sputum or other body fluids. The diagnosis is confirmed by isolating M. tuberculosis in cultures or rapid nucleic acid test probes.

Treatment

Regimens for TB have been developed for patients, depending on their HIV status, the prevalence of multidrug resistant disease in the community, drug allergies, and drug interactions. Uncomplicated TB in the non-HIV infected patient is typically treated with a four-drug regimen for 6 months. Regimens evolve: prescribers should consult published guidelines for current standards of care. Commonly used drugs include isoniazid (INH), rifampin (RIF), ethambutol (EMB), pyrazinamide, ciprofloxacin, and rifapentin. Medications are typically given in combinations rather than alone. A long course of therapy may be prescribed for patients co-infected with HIV/AIDS or for patients with drug-resistant bacilli. Multiply drug-resistant TB (MDR-TB) is tuberculosis resistant to either INH or RIF. Extensively drug-resistant TB (XDR-TB) is resistant to INH or RIF, any fluoroquinolone (e.g., ciprofloxacin), and at least one parenteral TB drug. Both MDR-TB and XDR-TB have very high mortality rates. See: multidrug resistant tuberculosis

CAUTION!

All patients with HIV should be tested for TB, and all patients with TB should be tested for HIV, because about one fourth of all patients with one disease will be infected with the other.

Patient care

All patients suspected of or confirmed to have TB should be placed in airborne isolation until they are no longer infectious. Health care professionals and visitors should wear particulate respirators when in the patient’s room. Patients should be taught to cough and sneeze into tissues, and to dispose of secretions in a lined bag taped to the side of the bed or in a covered disposal. The patient should wear a mask when outside the isolation room for any reason. Patients should be observed for complications such as hemoptysis, bone or back pain, and bloody urine. The patient and family or other support persons should be taught about the importance of regular follow-up visits, of following and completing the treatment regimen exactly as prescribed, of adverse effects to be reported, and of signs and symptoms of recurring TB. Persons who have been exposed to an infected patient should receive a TB test; chest x-rays and prophylactic INH also may be prescribed.

avian tuberculosis

A mycobacterial infection of birds caused by species including Mycobacterium avium. or M. genavense.

bovine tuberculosis

Tuberculosis of cattle caused by Mycobacterium bovis.

endogenous tuberculosis

Tuberculosis that reactivates after a previous infection.

exogenous tuberculosis

Tuberculosis originating from a source outside the body.

hematogenous tuberculosis

The spread of tuberculosis from a primary site to another site via the bloodstream.

latent tuberculosis

Infection with tuberculosis without active lung disease. It is detected by tuberculin skin testing.

miliary tuberculosis

Tuberculosis that spreads throughout the body via the bloodstream. It may be fatal.

multidrug resistant tuberculosis

Abbreviation: MDR-TB
Mycobacterium tuberculosis bacilli that are resistant to therapy with at least two standard antitubercular drugs (esp. isoniazid and rifampin, the two drugs that have formed the cornerstone of therapy for tuberculosis). MDR-TB must be treated with at least three antitubercular drugs to which the organism is presumed or proven to be sensitive. About 3% of cases of TB are drug-resistant.

open tuberculosis

Tuberculosis in which the tubercle bacilli are present in bodily secretions that leave the body.

tuberculosis

Infection with the organism Mycobacterium tuberculosis , either in the lungs (pulmonary tuberculosis) or in the LYMPH NODES (tuberculous ADENITIS), the skin (SCROFULA), the bones or in other organs. Pulmonary tuberculosis is usually acquired by aerosol spread from other people, while general (systemic) tuberculosis is transmitted in milk from cows with bovine tuberculosis. Pulmonary tuberculosis causes fever, fatigue, loss of appetite and weight, night sweats and persistent cough often with blood-streaked sputum and may spread to cause tubercular MENINGITIS or generalized (miliary) tuberculosis. Systemic tuberculosis causes areas of local tissue destruction often with SINUSES that discharge pus to the exterior. Tuberculosis is treated with a range of drugs used in various combinations for periods of up to a year. Antituberculous drugs include streptomycin, isoniazid, para-aminosalicylic acid (PAS), rifampicin, ethambutol and pyrazinamide.

tuberculosis

a contagious human disease (the consumption of Victorian times) affecting particularly the lungs, that is caused by the bacterium Mycobacterium tuberculosis. Response to infection is varied amongst individuals, some showing no signs while a few will die of the effects, these variations in host resistance being under genetic control. Tuberculosis is endemic in many parts of the world but, since the introduction of drugs and immunization with vaccines such as BCG, the world death rate has declined dramatically. A typical European mortality rate in 1900 was 190 per 100 000. This dropped to around 10 per 100 000 but is increasing worldwide due to the spread of AIDS.

uveitis

Inflammation of the uvea. All three tissues of the uvea tend to be involved to some extent in the same inflammatory process because of their common blood supply. However, the most severe reaction may affect one tissue more than the others as in iritis, cyclitis or choroiditis or sometimes two tissues, e.g. iridocyclitis. The symptoms also vary depending upon which part of the tract is affected. Acute anterior uveitis is accompanied by pain, photophobia and lacrimation and some loss of vision because of exudation of cells (aqueous flare), protein-rich fluid and fibrin into either the anterior chamber or vitreous body, as well as ciliary injection, adhesion between the iris and lens (posterior synechia), miosis and keratic precipitates. The condition is often associated with ankylosing spondylitis, rheumatoid arthritis, sarcoidosis, syphilis or tuberculosis (usually with granulomatous uveitis). It is the most common form of uveitis. Many cases are HLA-B27 positive. Treatment includes corticosteroids and mydriatics to reduce the risk of posterior synechia and to relieve a spasm of the ciliary muscle. See juvenile idiopathic arthritis; Reiter's disease; Busacca's nodules; Koeppe's nodules; sympathetic ophthalmia; Behçet's syndrome; phthisis bulbi; synchisis scintillans; Vogt-Koyanagi-Harada syndrome; Table I6.
fungal uveitis Uveitis caused by a fungus such as Candida albicans, Cryptococcus neoformans and Histoplasma capsulatum. It is often accompanied by other disorders (e.g. choroiditis, retinitis). It may have spread from other bodily tissues (e.g. skin, mouth, gastrointestinal tract) in patients who are intravenous drug addicts, patients with indwelling venous catheters or patients who are immunosuppressed.
intermediate uveitis A chronic inflammation of the ciliary body (cyclitis) or its pars plana zone (pars planitis) or of the peripheral retina and vitreous (peripheral uveitis). The cause is unknown in most cases but others are associated with systemic conditions such as multiple sclerosis, sarcoidosis or HIV infection. It affects mainly young adults and is bilateral in about 80% of cases. Symptoms are floaters and, sometimes, blurred vision, and there may be anterior chamber cells and flare. Ophthalmoscopic examination may show vitreous condensation and gelatinous exudates ('cotton balls' or 'snowballs'). Snowbanking, i.e. a whitish plaque or exudates involving the pars plana, often the inferior part of it, appears mainly in pars planitis. Intermediate uveitis may be associated with retinal vasculitis (i.e. inflammation of a retinal blood vessel). In a few cases the condition is self-limiting within a few months. However, in most cases the condition lasts several years may lead to complications such as cystoid macular oedema, posterior subcapsular cataract, retinal detachment or cyclitic membrane formation. Treatment includes corticosteroids and in resistant cases immunosuppressive agents.
posterior uveitis A uveitis involving the posterior segment of the eye. Symptoms include floaters and visual loss if the choroiditis involves the macular area. Ophthalmoscopically there is an accumulation of debris in the vitreous and choroidal lesions appear as yellow-white areas of infiltrates surrounded by normal fundus. Retinitis is also present in most cases, as well as retinal vasculitis. Posterior uveitis may be associated with AIDS, Behçet's disease, Lyme disease, histoplasmosis, sarcoidosis, toxoplasmosis, syphilis, tuberculosis, Vogt-Koyanagi-Harada syndrome, sympathetic ophthalmia, etc.
viral uveitis Uveitis caused by a virus. Common viruses are: herpes simplex, which is usually associated with keratitis and may cause anterior uveitis; herpes zoster which may also be associated with keratitis; human T-cell lymphotrophic virus; measles; cytomegalovirus; rubella; human immunodeficiency virus (HIV). See herpes simplex blepharoconjunctivitis; herpes zoster ophthalmicus.

tu·ber·cu·lo·sis

(TB) (tū-bĕr'kyū-lō'sis) A specific disease caused by infection with Mycobacterium tuberculosis, the tubercle bacillus, which can affect almost any tissue or organ of the body; most common site is in the lungs. [tuberculo- + G. -osis, condition]

Patient discussion about tuberculosis

Q. Can a low back pain start from picking up something from the oven? My mother has a low back pain. It started five days ago while she picked up a cake from the oven. the pain is always there, it bugs her while she sleeps and it excruciate while she is doing her regular physical activity.What can it be? should we go to our GP? Is there anything we can do to ease the pain except Tylenol? Just for the record my mom is 69 years old, and she has tuberculosis and a heart disease. A. This is a case where your mom should have an examination by a professional. A chiropractor would be the specialist to deal with back pain and can make any appropriate referrals if necessary.

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Patient discussion about tuberculosis

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