Comparison of fluconazole minimum inhibitory concentrations in three different formulations of RPMI-1640.

This study aimed to compare the susceptibilities of fluconazole, obtained in two laboratories, using three RPMI-1640 formulations (manufacturers') and inhibition standards (80%). A total of 39 selected Candida species (in vitro susceptible and resistant) and Cryptococcus neoformans isolates were tested in each medium by broth macro- and microdilution procedures following the National Committee for Clinical Laboratory Standards proposed reference method (M27-P). Macrodilution minimum inhibitory concentrations (MIC80%) were the lowest drug concentrations with turbidity (growth) less than or equal to that of the specific 80% inhibition standards (1:5 growth control). Microdilution MIC-2 were the lowest drug concentrations in which there was prominent decrease in growth. In general, the three formulations of RPMI-1640 medium provided similar MICs for most of the yeasts tested in both laboratories and by each test.