Etiology of oral candidiasis in patients with oropharyngeal cancer.

e18068 Background: The purpose of this study was to assess the etiology of oral candidiasis in patients with oropharyngeal cancer as potential causative agents of invasive candidiasis and to analyze in vitro activity of isolates of Candida fungi to caspofungin, fluconazole and voriconazole. Methods: Isolates were obtained in a prospective study from the oral mucosa of patients with oropharyngeal cancer in 2020-2021. Identification of Candida fungi was performed using MALDI-TOF MS. Result of activity of isolates to caspofungin, fluconazole and voriconazole after 24 hours of incubation were registered according to CLSI M60-ED2:2020 (Performance Standards for Antifungal Susceptibility Testing of Yeasts). Results: 45 patients aged 30-85 years were examined. 92 isolates of Candida fungi were obtained: C. albicans 31.5% (29) and Candida non albicans 68.5% (63). Candida non albicans included: C.parapsilosis 30.2% (19), C.glabrata 28.6% (18), C.krusei 19.0% (12), C.tropicalis 15.9% (10), C.guilliermondii 6.3% (4). Candida carriage on the oral mucosa was noted in 62.2% of patients in the first days of hospitalization, with a predominance of C. albicans 42.8% compared with 32.1% after chemotherapy (p = 0.003) and 25.0% after antibiotic therapy. The distribution of species varied depending on the age of patients. The table presents comparative activity of caspofungin, fluconazole and voriconazole (susceptible (S), moderately resistant (I), resistant (R)) in % to Candida spp. High sensitivity to caspofungin was noted for both C.аlbicans and Candida non albicans. Voriconazole was characterized by lower sensitivity and natural resistance in C.glabrata which makes it less suitable for empirical therapy, as well as fluconazole. Conclusions: Candida non albicans (68.5%) were predominant in the oral candidiasis etiology in patients with oropharyngeal cancer, which was probably due to the use of azole antimycotics for prevention and empirical therapy. Reduced activity to voriconazole and fluconazole was observed in the dominant isolates, given the natural resistance of C. krusei to fluconazole and C. glabrata to voriconazole. Acquired azole resistance was noted for C. parapsilosis and C. albicans. The pathogen type should be determined in all cases of invasive candidiasis to exclude natural resistance and sensitivity to azoles before starting therapy.[Table: see text]