[Persistence of mycobacteria in the host: epidemiology, immunopathology and prophylaxis].

Tuberculosis continues to be one of the major causes of morbidity and mortality in the developed and developing countries. There are more than 5000 cases of active open tuberculous lung disease in Germany. Worldwide approximately 10 million persons get tuberculous infections each year. Other not yet infected people in the community are endangered by this disease, especially those with immunodeficiency e.g. AIDS-patients or tumor patients. M. tuberculosis with its unique glycolipid cell wall is fairly resistant against the immune system. Only specialized activated macrophages are able to inhibit its growth. The bacteria may persist for years in the living body, probably in granulomas. A positive tuberculin-reaction indicates an infection and persistance of mycobacteria but does not prove a disease. Approximately 1.5 billion people are tuberculin positive worldwide. Any weakening of the immune system can unleash M. tuberculosis to cause reactivation and active tuberculous disease. The main diagnostic tools since the time of Robert Koch are microscopy and culture. Neither immunoserology nor polymerase chain reaction are of significant diagnostic value until now. It is possible to cure each new tuberculosis case by adequate and continuous therapy. Resistance of M. tuberculosis against the "classical" antituberculotic agents mainly arises from non-compliance of treated patients. Multiresistant strains make tuberculosis incurable. In Germany, in contrast to some regions in Africa, Asia or in the United States of America, resistance against one of the antituberculotic drugs is still relatively low (5-10%). BCG-vaccination is recommended for high risk-groups only. Preventive chemotherapy is indicated for persons with conversion of tuberculin-reaction from negative to positive. The main infectious danger results from individuals with undiscovered active tuberculous lung disease via airborne droplet transmission. Therefore the most important task is to discover these persons in time by always considering the disease, when the corresponding symptoms are being observed. Because of the mentioned problems new efforts should be done to investigate the pathogenesis of the disease and its therapy with alternative drugs.