Prevalence and susceptibility profiles of oral yeast species isolated from a healthy adult Thai cohort.

Objective: As the emerging resistance of Candida species to common antifungals is a major global concern, we assessed the antifungal susceptibility of oral yeast isolates from a healthy, Thai adult cohort, and correlated the yeast prevalence with oral disease indices.

Methods: Oral rinse samples collected from 100 Thai adults were concentrated and cultured on CHROMagar Candida. The yeasts were then isolated, identified and finally speciated using Matrix Assisted Laser Desorption ionization-time of flight mass spectrometry. Their antifungal sensitivity against fluconazole, itraconazole, voriconazole, and amphotericin B were investigated using standard Etest strips. The decayed, missing, filled teeth (DMFT) and the periodontal health were recorded and correlated with mycological data.

Results: The overall oral yeast prevalence was 25%. C. albicans was the commonest species isolated, followed by C. tropicalis and C. dubliniensis. Non-albicans-Candida was noted in approximately one-third, and included C. lusitaniae and C. nivariensis; Trichosporon asahii, was also detected in one subject. A majority of C. albicans isolates, (> 54%), exhibited resistance to fluconazole and voriconazole, while approximately a quarter (27%) were resistant to itraconazole. The vast majority (92%) however, were susceptible to amphotericin B. Those with oral yeasts had a significantly higher DMFT score (p < 0.05).

Conclusion: The resistance of a majority of Candida spp. to common azoles, described here for the first time in a Thai cohort, is disconcerting, and appear to confirm the creeping emergence of antifungal resistance globally. An incidental finding was the positive correlation between oral yeast carriage and DMFT score in Thai subjects.