[Atypical mycobacteria (MOTT): incidence and significance]

Statistics on the number, species and diagnosis of mycobacteria isolated from human specimens in 1981 at the Institute of medical microbiology of the University of Zurich are presented. 83% of the strains obtained from patients were classifiable as typical mycobacteria whereas 17% proved to be MOTT (mycobacteria other than tubercle bacilli). The clinical significance of the isolated species was assessed according to the criteria of Yamamoto et al. (Amer. Rev. resp. Dis. 96, 773-778 [1967]) and Wolinsky (Amer. Rev. resp. Dis. 119, 107-159 [1979]). Only in one out of 40 patients from whom MOTT (M. avium) was isolated could a causal connection be assumed between the isolate and the patient's disease. All microscopic determinations of specimens containing MOTT yielded negative results except that described above (in which 3 smears out of 6 were positive). Several Swiss laboratories have recently reported a significant increase in MOTT isolates.