Problems in the laboratory assessment of antifungal activity.

The end points of tube dilution tests for minimal inhibitory concentrations of miconazole and flucytosine against Candida albicans were difficult to evaluate because partial inhibition was noted over a wide range of antifungal concentrations. This problem was not encountered with amphotericin B. Partial inhibition of Candida arose because of reductions in yeast growth rate and of cell yield. Different sizes of yeast inocula were differentially inhibited by the same concentration of antifungal agent. An in vitro apparatus was described in which miconazole formulated as commercial creams, pessaries and medicated tampons for intravaginal application could be assessed for its inhibitory action in vitro.