GENETIC DIVERSITY IN CLINICAL ISOLATES OF THE DIMORPHIC FUNGUS BLASTOMYCES-DERMATITIDIS DETECTED BY A PCR-BASED RANDOM AMPLIFIED POLYMORPHIC DNA ASSAY

Blastomyces dermatitidis is a dimorphic fungus causing localized or sy stemic infection in areas where the organism is endemic in the central and southeastern United States, In this study, 19 independent isolate s of B. dermatitidis from Little Rock, Ark., were grouped into three c lasses based on restriction fragment length polymorphism patterns in m itochondrial DNA with a heterologous probe from Histoplasma capsulatum . One large class of 15 isolates and two smaller classes (classes 2 an d 3), each consisting of two isolates, were observed in Bg/II digests. Strain-specific arrays of PCR-amplified DNA products were obtained wi th arbitrarily selected primers (18 to 29 nucleotides long; G+C conten ts, 33 to 56%). In the large class 1 group, 13 isolates could be diffe rentiated by the random amplified polymorphic DNA (RAPD) method with v arious primers, The two remaining class 1 isolates were obtained from the same patient and produced identical RAPD arrays, Dissimilar RAPD p atterns were obtained from the smaller class 2 group but not from the class 3 isolates, Significant genetic diversity in clinical isolates o f B. dermatitidis was observed; this may underscore a similar environm ental diversification, Further application of the typing techniques ma y provide significant insight into the epidemiology of blastomycosis a nd aid in the assessment of specific virulence phenotypes.