Characteristics of 17 Paracoccidioides brasiliensis isolates

Abstract

We have studied the physiological and morphological features of 17 isolates of Paracoccidioides brasiliensis in order to define their phenotypes. The isolates were cultured at room temperature on potato dextrose agar (PDA, Difco) slants for mycelial growth and in 1% dextrose brain heart infusion agar (BHIA, Difco) at 37~ for the study of yeast forms. Most mycelial and yeast forms grew well between pH 5.6-9.4. In their response to osmotic pressure the isolates were separated in three groups: intolerant, intermediate and tolerant. They also varied in carbohydrate assimilation tests, which indicated important metabolic variation. No clear differences were observed in phenol oxidase tests, KNO3, starch, casein and arbutin assimilation tests. Only 1 of the isolates, Bt-19, had gelatinase activity. No correlation was observed between the above differences and virulence. Two patterns of growth were observed in the mycelial cultures, glabrous and cottonous, the latter being correlated with increased virulence for ddY mice. Most yeast forms grew as cerebriform colonies, but Pb-HC and Bt-19 colonies had a cobblestone-like surface.

Physiological characters of Sporothrix schenckii isolates - Physiologische Merkmale von Sporothrix schenckii-Isolaten

“…We found a similar result with all those isolates of S. schenckii. In a similar study, with isolates of Paracoccidiodes brasiliensis, Sano et al found that mycelial forms rather than yeast forms could split urea [22]. In the present study, 91.8% of the isolates could tolerate a maximum of 7% salt concentration in their mycelial form whereas 24% of yeast forms tolerated a salt concentration of up to 11%.…”

“…There is no study available to compare the pH and osmotolerance of S. schenckii strains. However, in the report of Sano et al a majority of P. brasiliensis strains grew well between pH 5.6 and 9.4 and but had variable osmotolerance [22].…”

“…These physiological parameters have not been previously evaluated for S. schenckii. In the report of Sano et al P. brasiliensis isolates were found to assimilate KNO 3 but gave variable results in casein hydrolysis and gelatinase activity [22].…”

Characterization and functional analysis of the β-1,3-glucanosyltransferase 3 of the human pathogenic fungusParacoccidioides brasiliensis

“…This leads to a detectable mutant phenotype characterized by reduced growth, roundcell morphologies, sensitivity to CW, increased cell wall permeability and secretion (Popolo & Vai, 1999;Vai et al, 2000). In fact, yeast forms did not grow below pH 3.6; most of the clinical isolate strains require a pH of culture medium above 5.6 and the establishment of yeast infection takes place in host tissues at pH values close to neutrality (Franco, 1986;Sano et al, 1997;Restrepo et al, 2001). Similar results were found for GAS4 of S. cerevisiae, a paralogue of GAS1, encoding a protein specialized to function at a pH value close to neutrality (Ragni et al, 2007a).…”

“…This requirement could reflect both the environmental growth conditions of P. brasiliensis and the pH of the niches colonized by this dimorphic pathogen. In fact, yeast forms did not grow below pH 3.6; most of the clinical isolate strains require a pH of culture medium above 5.6 and the establishment of yeast infection takes place in host tissues at pH values close to neutrality (Franco, 1986;Sano et al, 1997;Restrepo et al, 2001).…”