Infection and disease due to the environmental mycobacteria

Saprophytic mycobacteria are widely distributed in the environment and contact between them and man is unavoidable. Immunologically effective contact is responsible for cross-reactivity to tuberculin and there is increasing evidence that it also profoundly affects the nature of subsequent responses to BCG vaccination and to infection by the tubercle and leprosy bacilli. Some environmental mycobacteria occasionally cause overt disease. Two species, Mycobacterium ulcerans and M. marinum, cause characteristic named diseases: Buruli ulcer and swimming pool granuloma respectively. Other species cause pulmonary and non-pulmonary lesions that resemble those of tuberculosis. Disease often, but not always, occurs in individuals with predisposing factors such as damaged lungs or immunosuppressive disorders including AIDS. Diagnosis rests on the isolation and identification of the causative species and treatment is based on antituberculous therapy for extended periods or combinations of various other drugs. In contrast to tuberculosis, the incidence of these diseases appears to be on the increase in the Western world and they merit serious consideration.