Dual infection by "+" and "-" mating types of Ajellomyces (Blastomyces) dermatitidis.

A culture of Blastomyces dermatitidis isolated via bronchial washing from a patient with blastomycosis was studied intensively. The primary isolate was shown to have contained both the "+" and "-" mating type determiners of Ajellomyces dermatitidis. This was evidenced by the observations that both a first and a second subculture, when paired with itself produced fertile ascocarps typical of A. dermatitidis. Both these subcultures determined the production of ascospores when paired individually with each of six testers, these testers not producing fertile fruiting bodies when selfed. Isolation by micromanipulation of "+" and "-" ascospores from ascocarps produced by selfing a subculture established the mixed ("+", "-") nature of the clinical isolate and of the infection. The mixed infection was considered to have resulted from inhalation of both the "+" and "-" ascospores or conidia of A. dermatitidis or from the inhalation of one spore that contained both the "+" and "-" mating type determiners.