Phenotypic characterization and ecological features of Coccidioides spp. from Northeast Brazil

This study extends phenotypic and ecological knowledge of Coccidioides spp., by describing its recovery from soils of Ceará State (Northeast Brazil) and analyzing the in vitro features of the growth of its vegetative phase. Following a human coccidioidomycosis case, Coccidioides spp. strains were isolated from 3 of 14 soil samples collected in an armadillo's burrow. Mycological analysis showed colonies with glabrous, velvety or cottony texture and an increasing quantity of arthroconidia. The overall growth rates of the strains were slower in 8% NaCl medium, maximum growth rate was obtained at 30 degrees C, and their pH tolerance ranged from 4.0 to 11.0. Several carbohydrates and polyalcohol sources could be efficiently metabolized by Coccidioides spp. strains in the mycelial form. Total absence of growth was observed in media supplemented with either L-aspartic acid or L-histidine. Whereas intense growth was found when strains were incubated with any other aminoacid sources studied. Coccidioides spp. strains did not grow in the presence of Tween 60 and Tween 80, but exhibited intense growth in Tween 20. Nicotinic acid and the toxic compounds caffeic acid and phenol could not be metabolized by any strain. All of the strains were positive for urease production and displayed intense growth in media containing cycloheximide concentrations ranging from 0.01 and 0.05%, but did not grow at 0.1 and 0.2%. The present findings confirm the importance of armadillos burrows in the ecology of Coccidioides spp. in Northeast Brazil and indicate that the fungus is a very physiologically versatile organism.