The changes of antifungal susceptibilities caused by the phenotypic switching of Candida species in 229 patients with vulvovaginal candidiasis

Abstract

Objective: This study was to investigate the changes of antifungal susceptibilities caused by the phenotypic switching in patients with vulvovaginal candidiasis (VVC).

Methods: 229 women were enrolled in this study. The vaginal smears of these patients were collected and gram stained for fungal microscopic observation. The vaginal discharge of them in cotton swabs was cultured in sabouraud's agar with chloramphenicol medium. After fungal culture, fungal identification was analyzed using CHROM agar Candida chromogenic and identification medium. Then, the in vitro antifungal susceptibility testing was carried out using the standardized CLSI M27-A2 broth microdilution method.

Results: 64.63% of Candia species in patients with VVC were Candida albicans and the remainders were non-albicans Candida species. The phenotypic switching was observed in 91.22% of C. albicans infection. In antifungal susceptibility testing, the susceptible rates of C. albicans to voriconazole, fluconazole and itraconazole were significantly higher than that of non-albicans Candida species (P = 0.00, 0.00, 0.00). No matters in patients infected with C. albicans or with non-albicans Candida species, the susceptible rate to fluconazole of the clinical isolates with phenotypic switching was significantly higher than that without phenotypic switching (P = 0.01, 0.01).

Conclusions: In the study, C. albicans was the commonest pathogenic species in patients with VVC, in which the phenotypic switching was easy to occur. The susceptible rates of C. albicans to all antifungal drugs were higher than that of non-albicans Candida species. The susceptible rate to fluconazole was all influenced by the phenotypic switching in C. albicans and non-albicans Candida species.

Keywords: Candida albicans; non-albicans Candida; antifungal susceptibility testing; phenotypic switching; susceptible rate.

Figure 1

The colors of Candida species in CHROMagar Candida chromogenic and identification medium. The color of green and purple represents C. albicans and C. glabrata, respectively; the color of soft pink and blue‐gray represents C. krusei and C. tropicalis, respectively

Figure 2

The colors of two Candida species in CHROMagar Candida chromogenic and identification medium. The color of iron blue and white represents the C. tropicalis and C. parapsilosis, respectively

Figure 3

A, the presence of pseudohyphae under microscopic observation (with phenotypic switching) (Gram staining, 1000×); B, the presence of yeasts without budding under microscopic observation (without phenotypic switching) (Gram staining, 1000×)