Experimental hematogenous candidiasis caused by Candida krusei and Candida albicans: species differences in pathogenicity.

Hematogenous infections caused by Candida krusei have been noted with increasing frequency, particularly in cancer patients receiving prophylaxis with antifungal triazoles. Progress in understanding the pathogenesis of this emerging infection has been limited by the lack of an animal model. We developed a CF1 mouse intravenous inoculation model of candidiasis to evaluate the pathogenicity of C. krusei in normal and immunosuppressed mice and to compare it with that of Candida albicans. Several inocula (10(6) to 10(8) CFU per animal) of two clinical strains of C. krusei and three American Type Culture Collection strains of C. albicans were tested. Groups of 20 mice each were injected with a single intravenous dose of one inoculum. Animals randomized to receive C. krusei were immunosuppressed by intraperitoneal injection of cyclophosphamide or the combination of cyclophosphamide plus cortisone acetate or they did not receive immunosuppressive agents (normal mice). One hundred percent mortality was observed in normal mice injected with 10(6) CFU of C. albicans per mouse compared with no mortality in normal mice that received 10(8) CFU of C. krusei per mouse (P < 0.01). Resistance to C. krusei infection was markedly lowered by immunosuppression, particularly by the combination of cyclophosphamide plus cortisone acetate, with a significantly shorter survival and a higher organ fungal burden in immunosuppressed than in normal animals (P < 0.01). Tissue infection was documented by culture and histopathologic findings in all examined organs.