Some strains, moreover, are resistant to penicillin due to altered penicillin-binding proteins. Dissemination has been associated with strains that have increased ability to survive in human serum. This may be an intrinsic difference related to absent components of the complement system in the host. Blastomycosis is a pyogranulomatous disease caused by the dimorphic fungus Blastomyces dermatididis. Attempts to isolate the organism in its natural habitat have been unsuccessful until recently when the association of this fungus with soil enriched by beaver feces was noted.
Initial infection is through the lungs , usually followed by hematogenous dissemination.
Clinical disease most often involves lungs, skin, bones, and genitourinary tract. In nature or on media at room temperature, Blastomyces dermatididis grows as a mycelial form. In humans or on enriched media at 37oC, the organism grows as a yeast form. Yeast forms have a characteristic thick cell wall that is highly refractile. These cells reproduce by single buds with a broad base between parent and bud.