Blastomycosis-epidemiology and biology of its etiologic agent Ajellomyces dermatitidis.

Abstract

From this review of previous publications and unpublished data it was concluded that there was little evidence that blastomycosis is contagious. Yet in spite of some reports thatB. dermatitidis has been isolated from soil no claim has been made that the ecologic niche in nature has been found. The logical assumption that soil is the natural habitat of the pathogen has been made less certain by demonstrations that this fungus, unlikeHistoplasma capsulatum, soon disappears from natural soils into which it is introduced. Furthermore,B. dermatitidis is lysed by microorganisms obtained from such soils. Therefore it was considered to be questionable how much epidemiologic significance is to be applied to chance contaminations of soil by animals with blastomycosis. Only one species ofAjellomyces dermatitidis, the heterothallic, perfect stage ofB. dermatitidis, may exist in the United States of America. Evidence for this was obtained through pairing cultures isolated in that country since ascospores were produced when an isolate from a dog was paired with an isolate from a person and fertile cleistothecia were produced by pairing isolates from widely distributed geographic regions. Individual pairings of 6 African isolates with testorB. dermatitidis strains from the U.S.A. resulted in each case in production of ascocarps. However, unquestioned ascospore production has not been obtained, although a few spherical cells having the dimensions of ascospores have been found in some cleistothecia. On this, and the other evidence so far obtained, it was concluded that the African isolates are closely related to the American isolates and could belong to the same species.