天津医科大学内科学课件 Tuberculosis.pptVIP

Tuberculosis This Disease This disease, which a few years ago was considered to be almost under control in Western Europe and North America, has once again become a serious world-wide problem because of AIDS. However, in developed countries there is still a tendency for tuberculosis to be overlooked, the diagnosis being made late or only at autopsy. General Considerations Mycobacterium tuberculosis is still an important pathogen. Approximately one-third of the world’s population is infected with M tuberculosis, according to World Health Organization estimates, resulting in 2.9 million annual deaths. In the United States, tuberculosis is on the rise, after several decades of steady decline. Those at greatest risk of acquiring tuberculosis Children, adolescents and young adults Contacts of patients with smear-positive pulmonary disease Immunocompromised individuals (e.g. AIDS patients and those on immunosuppressive therapy and corticosteroids) Those in close contact with many potential patients (e.g. health workers) Underprivileged people living in overcrowded conditions Pre-existing conditions-diabetes mellitus, gastric surgery, silicosis, alcoholism Aetiology Several types of mycobacteria are responsible for disease in humans, as shown in the next. Mycobacterium tuberculosis-cause of most infections Mycobacterium bovis-endemic in cattle, spread to humans by milk Mycobacterium kansasii Mycobacterium xenopi Mycobacterium malmoense MAIS complex-Mycobacteriurn avium, Mycobacterium intracellulare, Mycobacterium scrofulaceum Entry of the tubercle bacillus into the body or the alimentary or respiratory tract is not necessarily followed by a clinical illness, the development of which is dependent upon several other factors. Epidemiology In the United States, tuberculosis had been on the decline until 1985, when the number of cases began to increase. One lesson learned from the resurgence of tuberculosis and multidrug-resistant tuberculosis is the importance of t