Germ tube formation and proteinase activity of Candida albicans in relation to virulence for mice.

Standard strains and clinically isolated strains of Candida albicans were tested for their virulence for mice. Lethal effects of yeast forms of clinical isolates were stronger than those of germ tube-forming cells in all except one strain. The germ tube of C. albicans JCM1542 killed mice earlier than the yeast form. Proteinase activity of the clinically isolated strains from patients with dental caries and xerostomia was negatively correlated with median survival time (MST) of mice which were injected with 1 x 10(6) yeast form cells. The yeast forms of the standard strains had a weak lethal effect on mice compared with their proteinase activity and the yeast forms of the clinical isolates from patients with acute pseudomembranous candidiasis and denture stomatitis had a highly lethal effect with relatively low proteinase activity. These results indicate that the virulence of C. albicans in partially due to proteinase activity.