The Investigation of the Susceptibility of Various Candida Species to Two Different Triazoles by Microdilution Method

Objective: In recent years, there has been an increasing trend in the isolation of candida species that cause opportunistic and nosocomial infections and are resistant to antifungals; thus, the identification of candida strains at species-level and the use of antifungal susceptibility tests have become obligatory. The aim of this study was investigate the susceptibilities of fluconazole and voriconazole isolated from blood cultures.

Materials and Methods: Strains included in the study were identified to the species level by using germ tube test, microscopic evaluation of the growing type on cornmeal-Tween80 medium, and colonial morphology on CHROM agar. Moreover, the API 20C AUX identification kits were also used for the identification. Of the strains tested, 30 (34.1%) were C. albicans; 26 (29.5%) were C.tropicalis; 15 (17.1%) were C.parapsilosis; 8 (9.1%) were C.glabrata; 5 (5.7%) were C.kefyr, and 4 (4.5%) were C. krusei. Two standard candida species (C. krusei ATCC 6258, C. parapsilosis ATCC 22019) were also included in the study. The susceptibilities of the identified species to fluconazole and voriconazole and MIC ranges with MIC 50/90 values were determined for each agent. Microdilution technique which was recommended by Clinical Laboratory Standards Institute M27- A2 was used for this purpose.

Results: Eight candida strains were dose-dependent susceptible (MIC value 16-32μg/ml); 5 candida strains were resistant (MIC value≥64μg/ml) to fluconazole. Of dose-dependent susceptible strains, 3 were C.albicans: 3 were C.tropicalis; 2 were C.glabrata. Of the resistant strains, one was C.albicans and 4 were C.krusei. MIC ranges for fluconazole were 0.125-64 μg/ml and for voriconazole, 0.125-1 μg/ml for all the candida strains. MIC values were ≤1 μg/ml for voriconazole in all the studied strains. Low MIC values detected for voriconazole were also dose dependent susceptible and resistant to fluconazole.

Conclusion: Considering the MIC values, it can be said that voriconazole may also be effective for candida strains and may also be an alternative for the fluconazole resistant strains.