Antifungal susceptibility profile of yeast isolates from sterile sites at a tertiary hospital in South Africa

Invasive infections caused by yeasts are associated with high mortality and morbidity, and resistance to antifungal agents is increasing. Candida spp. has emerged as the leading cause of systemic nosocomial fungal infections. The aim of this study was to identify yeast isolates from sterile site specimens to species level, and to determine their susceptibility to fuconazole and voriconazole, at the National Health Laboratory, Service Dr George Mukhari Tertiary Laboratory from March to August 2007. Candida isolates were identifed to species level using a germ tube test and/or Api® ID 32C kits. Antifungal susceptibility testing to fuconazole and voriconazole was performed using the disc diffusion method in accordance with the Clinical and Laboratory Standards Institute guidelines. All of the Candida isolates were from the neonatal intensive care unit (NICU), with the exception of two. The distribution of yeast isolates was as follows: C. krusei (41.9%), C. albicans (32.3%), C. inconspicua (5.5%), C. parapsilosis (2%), C. tropicalis (1.5%), C. sake (1.5%), C. lambica (1.5%), and C. valida (0.5%). Cryptococcus neoformans (11%), C. albidus (0.5%), Rhodotorula glutinis (1%), and C. humicola (0.5%) were also isolated. Of the isolated C. albicans, 61% were susceptible to fluconazole. A possible C. krusei outbreak could have occurred in the NICU during the study period. Voriconazole was the most susceptible antifungal agent to various yeast pathogens. The results of this study on azoles susceptibility testing of yeasts show that voriconazole may prove to be a valuable alternative antifungal agent in this tertiary hospital for the treatment of infections caused by yeasts, including Candida spp.