Screening for anti-fungal resistance in Candida species using chromogenic agar dilution

Abstract

Background: The wide use of azoles for the prevention and treatment of candidiasis is due to the high morbidity and mortality associated with this nosocomial infection. Consequently, drug resistance has emerged among Candida species. The current study aimed to compare between the VITEK-2 and the chromogenic media as regards the identification of Candida species and antifungal susceptibility testing (AFST) using agar dilution of different antifungals with multiple concentrations. Methods: This cross-sectional study was conducted on 160 Candida isolates collected from different specimens submitted to the Central Microbiology Laboratory of Ain Shams University Hospitals from February 2020 to February 2021. The VITEK-2 system and Brilliance Candida agar media were used for identifying the isolates to species level. Then, AFST was performed by the VITEK-2 system and agar dilution method on Brilliance Candida agar media. Fluconazole, Voriconazole and Micafungin dilutions were prepared as per the Clinical and Laboratory Standards Institute (CLSI). Results: Regarding the identification of Candida species, there was an almost perfect agreement (KAPPA= 0.9) between the VITEK-2 and Brilliance Candida agar. C. tropicalis was the most common species, with predominance among urine specimens. AFST using fluconazole showed 88.5% susceptibility, 7.6% susceptible dose dependent (SDD) and 3.8% resistance. While for Voriconazole, 95.0% were susceptible, 4.4% were intermediate, and 0.6% were resistant. Concerning Micafungin, 98.7% and 1.3% were susceptible and resistant, respectively. Conclusion: The chromogenic media proved to be a reliable and cost-effective method for identification of common candida spp. and for identification of mixed candida infections. AFST using agar dilution on chromogenic media showed high accuracy when used with fluconazole.