Susceptibility and MIC determination versus caspofungin in Candida albicans and Candida tropicalis multiresistant isolates [Determinación de sensibilidad y CMI de caspofungina en cepas multirresistentes de Candida albicans y Candida tropicalis mediante la técnica de microdilución]

Abstract

Background. The strains of the genus Candida have currently acquired importance as pathogens in nosocomial infections because of their ability to generate resistance. Echinocandins are a group of antifungals of recent use, but the automated equipment still does not observe the determination of minimum inhibitory concentration (MIC) for these drugs. Material and method. We isolated 10 strains of the genus Candida resistant to fluconazole from pediatric patients. They were subcultivated, and standardized to perform the test against caspofungin by microdilution technique in 96-well plates, with a RPMI medium with L-glutamine and a pH indicator buffered with MOPS (based on the document NCCLS M27-A2). MIC was defined as the lowest concentration in which there is no growth after 24, 48, and 72 hours of incubation at 35°C and 37°C. Results. After 48 hours of the assay at 35°C. MIC was 0.615 μg/ml for C. albicans and C. tropicalis. There is no resistance to caspofungin in any of the samples. Conclusion. We identified the better conditions for the determination of sensibility and MIC of C. albicans and C. tropicalis through the technical of microdilution for caspofungin. Discussion. Caspofungin has been used as an alternative for the treatment of disseminated fungemias with strains of the genus Candida with resistance to usual treatment. Commonly this type of fungemia is treated with amphotericin B, which presents a range of adverse effects, that echinocandins do not have and exhibit favorable pharmacokinetic properties, depending on the dose.