Efficacies of fluconazole, caspofungin, and amphotericin B in Candida glabrata-infected p47phox-/- knockout mice

Abstract

Candida glabrata is the second leading cause of adult candidemia, resulting in high mortality. Amphotericin B is considered the treatment of choice, while the efficacy of fluconazole is controversial and caspofungin efficacy is unknown. To ascertain drug efficacy in vivo, the utility of a murine model of C. glabrata infection was investigated. C. glabrata was found to cause progressive, lethal infection when injected intravenously into C57BL/6 mice with reduced oxidative microbicidal capacity due to knockout of the p47(phox) gene. Spleen and kidney organ CFU counts were determined in groups of mice 2 days after the mice completed 6 days of daily intraperitoneal drug treatment, which began on the day of infection. Daily injections of fluconazole at 80 mg/kg did not reduce spleen or kidney CFU counts after infection with C. glabrata strains having in vitro fluconazole MICs of 2, 32, or 256 microg/ml compared to saline-treated controls. However, this fluconazole regimen reduced spleen CFU counts in mice infected with Candida albicans, an infection that is known to be responsive to fluconazole. Caspofungin at 5 mg/kg and amphotericin B at 5 mg/kg were both effective in reducing fungal burden in spleens and kidneys of C. glabrata-infected mice. Ten mice treated for 6 days with caspofungin at 1 mg/kg survived for 15 days, though all 10 saline-injected mice died or were so ill that they had to be sacrificed by 96 h postinfection. This murine model provided evidence of the efficacy of amphotericin B and caspofungin but not of fluconazole against C. glabrata infection.

FIG. 1.

Survival of mice after inoculation with C. glabrata. Groups of five C57BL/6 (WT) or p47^phox−/− KO mice were inoculated intravenously with either 5.7 × 10⁶ (WT [⧫]; KO [▴]) or 5.7 × 10⁷ (WT [◊]; KO []) viable C. glabrata 40A.

FIG. 2.

Amphotericin B (AMB) treatment. Groups of five C57BL/6 (WT [solid symbols]) mice and five p47^phox−/− (KO [shaded symbols]) mice were injected intravenously with C. glabrata 12175 with inocula of 1.7 × 10⁷ for WT mice and 2.6 × 10⁵ for KO mice. Mice were given intraperitoneal AMB at 5 mg/kg or saline daily for 6 days and sacrificed 2 days later. Significant differences in organ colony counts between treated and control mice (P < 0.02) are indicated by an asterisk. The geometric means and the standard error are shown.

FIG. 3.

Treatment with caspofungin, amphotericin B (AMB), or saline. Groups of seven p47^phox−/− KO mice were injected intravenously with 5 × 10⁵ viable C. glabrata 18434 and intraperitoneally given caspofungin at 5 mg/kg, amphotericin B at 5 mg/kg, or saline daily for 6 days. The spleen (○) and kidney (□) tissue burdens were assessed 2 days later. Significant differences in organ colony counts between caspofungin- or amphotericin B-treated and control mice are indicated by an asterisk (P < 0.002). The geometric means and the standard errors are shown.

FIG. 4.

Survival of groups of 10 p47^phox−/− KO mice after intravenous inoculation with 5 × 10⁷ viable C. glabrata 18434 and treatment with caspofungin at 1 mg/kg () or saline () daily for 6 days.