Molecular identification and antifungal susceptibility testing of Candida species isolated from oral lesions in patients with head and neck cancer undergoing radiotherapy

Background and Purpose: Radiation therapy in patients with head and neck malignancies predisposes them to oral Candida colonization and infection due to damage of oral mucosa and destruction of the salivary gland. This study aimed to determine the prevalence of oropharyngeal candidiasis (OPC) in patients with head and neck cancer (HNC) undergoing radiotherapy (RT), identify the yeasts isolated from them, and determine their antifungal susceptibility.Materials and Methods: This cross-sectional study was conducted from December ۲۰۱۸ to June ۲۰۱۹ at two referral radiotherapy centers in northern Iran. Yeast strains that were isolated from patients with HNC were identified using conventional and molecular methods. The in vitro activities of eight common antifungal drugs against ۵۵ isolates were investigated according to the guidelines of the Clinical and Laboratory Standard Institute (M۲۷-A۳ and M۲۷-S۴) broth microdilution document.Results: Among ۵۹ patients receiving RT, the prevalence of OPC was ۲۱ (۳۵.۵۹%) and ۱۵ (۲۵.۴۲%) patients were diagnosed with colonization. The mean age of the patients was ۵۵.۳۲±۱۳.۳ years (within the range of ۲۷-۸۷ years). In this study, the pseudomembranous form was reported as the most clinical type of OPC. Candida albicans with the frequency of ۶۰% was the most common type of Candida spp. that was observed in this study, although non-albicans Candida spp., such as C. glabrata (۲۷.۲۷%), C. tropicalis (۵.۴۵%), C. parapsilosis (۳.۶۳%), C. krusei (۱.۸۳%), and C. kefyr(۱.۸۳%) were also isolated. Considering the low minimum inhibitory concentration range of amphotericin B, compared to fluconazole, administration of this agent is a more suitable antifungal drug for extensive oral candidiasis in these patients. Among azoles,clotrimazole had low efficacy and several studied isolates (۶۵.۵%) showed resistance.Conclusion: Correct diagnosis as well as determining drug sensitivity and risk factors are the effective steps in reducing the complications related to oral candidiasis in people undergoing RT.

Keywords:

Antifungal susceptibility test , Candida species , head and neck cancer , Oropharyngeal candidiasis , radiotherapy