Microdilution in vitro Antifungal Susceptibility Patterns of Candida Species, From Mild Cutaneous to Bloodstream Infections

BACKGROUND: Candida species, as opportunistic organisms, can cause various clinical manifestations, ranging from mild cutaneous infections to systemic candidiasis in otherwise healthy individuals. Remarkably, the incidence and mortality rates of candidemia have significantly increased worldwide, even after advances in medical interventions and the development of novel antifungal drugs. OBJECTIVES: Given the possible resistance to antifungal agents, susceptibility testing can be useful in defining the activity spectrum of antifungals and determining the appropriate treatment regime. MATERIALS AND METHODS: The in vitro susceptibilities of molecularly identified Candida strains (n = 150) belonging to seven species recovered from clinical specimens, including vaginal, cutaneous, sputum, bronchoalveolar lavage (BAL), and blood samples, were determined for six antifungal drugs (amphotericin B, fluconazole, itraconazole, voriconazole, posaconazole, and caspofungin), based on the clinical and laboratory standards institute’s M27-A3 and M27-S4 documents. RESULTS: Candida albicans was the most frequently isolated species (44.66%), followed by non-albicans Candida, including C. glabrata (20%), C. parapsilosis (13.33%), C. krusei (8%), C. tropicalis (7.3%), C. dubliniensis (4%), and C. africana (3.33%). Posaconazole had the lowest geometric mean minimum inhibitory concentration (MIC) (0.0122 µg/ml), followed by amphotericin B (0.0217 µg/mL), voriconazole (0.1022 µg/mL), itraconazole (0.1612 µg/mL), caspofungin (0.2525 µg/mL), and fluconazole (0.4874 µg/mL) against all isolated Candida species. Candida africana and C. parapsilosis were significantly more susceptible to fluconazole, compared to C. albicans and other Candida species (P < 0.001). However, their clinical effectiveness in the treatment of Candida infections remains to be determined. CONCLUSIONS: These findings highlight the importance of precise and correct species identification of clinical yeast isolates via molecular approaches, and of monitoring the antifungal susceptibility of Candida species recovered from clinical sources. Laboratories should consider routine MIC testing of C. glabrata isolates collected from sterile sites. Surveillance studies of Candida species and new analyses of antifungal treatment outcomes will allow more informed determinations of the value of these drugs in the antifungal armamentarium.