Distribution of the two mating types among Histoplasma capsulatum isolates obtained from an urban histoplasmosis outbreak.

The mating type distribution among the 28 Histoplasma capsulatum isolates obtained from the histoplasmosis outbreaks which occurred in Indianapolis in 1978-1979 and 1980-1981 was studied. The overall ratio of + and - types was 1:2.5. The isolates from disseminated patients showed a 1(+):1(-) ratio while the isolates from non-disseminated pulmonary cases showed a 1(+):4(-) ratio. The frequency of the + type in these outbreaks was three times higher than that of the previous study. This was due to an unusually high prevalence of the + type among the patients with disseminated histoplasmosis.