Susceptibility of Candida albicans to flucytosine when tested in different formulations of yeast nitrogen base broth

The influence of various formulations of yeast nitrogen base broth and temperature on the flucytosine sensitivity of Candida albicans was examined. Each of 15 isolates was tested concurrently in yeast nitrogen base from two different suppliers, with or without supplemental dextrose and L-asparagine, and with incubation at either 30°C or 37°C. Observed differences were related to media source, media supplementation, and temperature of incubation. For all three variables, higher endpoint results were associated with greater rates of yeast growth as reflected by turbidity after 24 hr of incubation. Despite these differences, their magnitudes were sufficiently small so that variations in yeast nitrogen base formulation appear not to be an important source of imprecision in susceptibility testing of yeasts.