SACCHAROMYCES-CEREVISIAE VIRULENCE PHENOTYPE AS DETERMINED WITH CD-1 MICE IS ASSOCIATED WITH THE ABILITY TO GROW AT 42-DEGREES-C AND FORM PSEUDOHYPHAE

Isolate origin was not a firm predictor of virulence phenotype, since the virulence phenotypes of clinical and nonclinical isolates ranged f rom virulent to avirulent and from intermediate to avirulent, respecti vely. Therefore, it,vas important to determine if there was any associ ation between putative virulence traits and virulence that might help explain the variation in virulence phenotypes. S. cerevisiae isolates spanning a range of virulence phenotypes in experimental infections we re examined for putative virulence traits: the ability to grow at supr aoptimal temperatures (42, 39, and 37 degrees C), gelatin liquefaction , casein utilization, and pseudohyphal formation. Gelatin liquefaction appeared to be unrelated to pseudohyphal formation on casein or to vi rulence. Significant differences in the ability to grow at 39 and 42 d egrees C were observed when the virulent and intermediate classes were compared with the avirulent class. Less extreme but still significant differences in pseudohyphal formation were observed when the virulent and intermediate classes were compared with the avirulent class. Ther efore, two virulence traits, similar to those identified in other path ogenic fungi, the ability to grow at elevated temperatures and pseudoh yphal formation, have been identified in S. cerevisiae.