Mycobacterium avium-intracellulare complex serovars isolated in South Africa from humans, swine, and the environment.

From 1968 to 1978 a total of 792 strains of the Mycobacterium avium-intracellulare complex were isolated from various sources in South Africa and serotyped according to Schaefer's seroagglutination test' 569 strains were from healthy rural persons, 171 strains were from lymph node lesions of swine, and 52 environmental strains were from animal feed and bedding, plants, dust, and soil. Serotyping was undertaken to determine the exposure of humans and animals to various serovars, to ascertain the predominance of individual serovars from the various sources, and to pinpoint, if possible, reservoirs of infection. Occurrence of M. avium serovars 1--3 was low in all sources studied: 1% in humans, 4% in the environment, and 14% in swine. The predominant human serovars were 7, 14, 19, 24, and 13, whereas the predominant swine serovars were 8, 4, double type 4/8, and 10. Serovars found in the environment were 9, 10, 13, 14, 16, and 17, with serovars 4 and 8 predominating.. Therefore, in South Africa, as in Australia, humans and animals are continuously exposed to various serovars, particularly serovars 4--24, which can be frequently and regularly isolated from the environment, the possible source of infection.