Etiological Agents of North and South American Blastomycosis. ∗

Abstract

A granulomatous fungus infection simulating scrofuloderma was described by Gilchrist in 1894. Since the fungus was seen in the diseased tissues as a budding, yeast-like organism, associated with a skin infection, it was called Blastomyces dermatitidis 1 and the disease blastomycosis. A number of different species of Blastomyces 2 and a number of variously named fungi 3 since reported from cases of North American blastomycosis have been shown to be either slight variations of Gilchrist's organism or to be Coccidioides immitis, 4 5 the causative agent of San Joaquin Valley Fever or coccidioidal granuloma.

South American investigators have described a granulomatous fungus infection as pseudococcidioidal granuloma 6 caused by a fungus first confused with Coccidioides immitis, 7 8 later named Paracoccidioides brasiliensis. 9 Moore, 10 however, showed that Paracoccidioides reproduced in the tissues by multiple-budding, thus indicating its relationship to Blastomyces, but retained the name Paracoccidioides and placed it in his family Coccidioideaceae in equal rank with Coccidioides and Rhinosporidium.

Although the stages in the life cycle of Blastomyces dermatitidis and Paracoccidioides brasiliensis have been studied by numerous investigators, 1 – 11 and Paracoccidioides has been compared with Coccidioides, 8 – 10 12 no detailed comparative study of the various forms of B. dermatitidis and P. brasiliensis has been made. In order to establish the identity of the South American fungus the present study was undertaken.

Seven strains‡ of Blastomyces, isolated from lesions of North American blastomycosis, and 6 strains‡ of Paracoccidioides, isolated from lesions of the South American disease, were compared as to their appearance in tissue, and their growth and microscopic appearance on various artificial culture media both at room and at incubator temperature. Blastomyces dermatitidis was seen in the tissues as single-budding, thick-walled, yeast-like organisms. When diseased tissue or pus from blastomycotic lesions was placed on Sabouraud's glucose agar, after varying periods of time at room temperature, the fungus developed into a cottony-mold-like growth.