Abstract
A proteinase-deficient mutant of C. albicans, M12, was produced by nitrosoguanidine mutagenesis of a proteinase-producing strain, ATCC 28366. The mutant was phenotypically identical to its parent in nearly all biochemical and morphological characteristics except proteinase production. The mutant was considerably less lethal than the parent when inoculated i.v. into mice and lower counts of C. albicans were recovered from the organs of mice infected with the mutant. Both strains were phagocytosed and killed to a similar extent by human and murine polymorphonuclear leukocytes when the yeasts were grown in a medium that did not induce proteinase production. In a proteinase-inducing medium, ATCC 28366 was phagocytosed and killed less well than M12. Evidently, proteinase secretion by C. albicans is 1 factor determining the virulence of the species, but that other virulence factors are also involved in the pathogenesis of systemic candidosis.