Identificación y susceptibilidad antifúngica de candida spp aisladas de micosis invasora: influencia del porcentaje de inhibición del crecimiento para la determinación de CIM / Identification and antifungal susceptibility of candida spp isolated from invasive mycoses: influence of growth inhibition percentage to determine minimal inhibitory concentration

RESUMO

Background: An increase in the frequency of resistant strains to antifungal drugs has been detected in the last decade. Aim: To report the minimal inhibitory concentration (MIC) to amphotericin B, fluconazole, ketoconazole and itraconazole. To compare the MIC obtained with 80 percent and 50 percent of growth inhibition to the azoles. Material and methods: Fifty yeast strains isolated between 1998 and 1999, from 17 adults and 33 children with invasive mycosis were studied. Susceptibility was determined by broth microdilution method with RPMI 1640 plus glucose 2 percent according to the National Committee for Clinical Laboratory Standards (1997). Results: The most frequently isolated strains were C albicans in 27 cases and C parapsilosis in 12. All isolates were susceptible to amphotericin B. According to the MICs obtained with 80 percent of inhibition, 12 strains had MICs considered as resistant to azoles. Five strains were resistant both to fluconazole and itraconazole. Considering MICs obtained with 50 percent of inhibition, only five strains were found resistant to azoles (p <0.05). Using this criterion, only one C glabrata strain was found to be simultaneously resistant to fluconazole and itraconazole. Conclusions: Similar results in the pattern of susceptibility of Candida spp to azoles, to those reported abroad, are obtained when the MIC is calculated using 50 percent inhibition