Introduction: We studied the species distribution and antifungal susceptibilities of Candida  isolates causing refractory or recurrent oropharyngeal candidiasis (OPC) in a multicenter study in China (2013–2016).
Methods: Species identification was performed using the Bruker Biotyper (Bruker Daltonics, Germany) matrix-assisted laser desorption/ionization time of flight mass spectrometry system supplemented by internal transcribed spacer sequencing as required. Antifungal susceptibilities were determined by the Clinical and Laboratory Standards Institute document (CLSI) M27-A3 broth microdilution methodology.
Results: A total of 558 non-duplicate Candida  isolates comprising 10 species were obtained from 535 patients. Candida albicans  was the most common species (89.6%), followed by C. glabrata  (5.2%), C. tropicalis  (2.9%), and C. parapsilosis  (0.7%). Azoles were active against C. albicans  with susceptibility rates of 96% and 95.8% for fluconazole and voriconazole, respectively. MIC₅₀ values of C. albicans  to fluconazole, voriconazole, itraconazole, and miconazole were 1, 0.03, 0.25 and 0.12 μg/mL, respectively, higher than those in previous studies of which OPC patients (corresponding MIC₅₀ values of 0.25 , 0.015 , 0.06 , and 0.03 μg/mL). Except for itraconazole, the MIC₅₀ and MIC₉₀ values of 58 non-C. albicans  to other azoles were two to threefold higher than C. albicans . Miconazole, amphotericin B, nystatin, and 5-flucytosine had good in vitro antifungal activity for all isolates.
Conclusion: The study provides valuable data on the species distribution and antifungal susceptibility of oropharyngeal Candida  isolates from geographically diverse areas of China. C. albicans  remains the most common species but with increasing rates of azoles resistance.
Keywords: oral candidiasis, Candida, identification, antifungal susceptibility