Differences in response in vivo to amphotericin B among Candida albicans strains

A group of ten Candida albicans strains previously determined to be resistant or susceptible to topical amphotericin B in vivo and in vitro were exposed to treatment with different concentrations of the drug in a quantitative model of candidal keratitis in Dutch-belted rabbits. After 5 days of topical treatment with amphotericin B eye drops in concentrations of 0.3%, 0.03%, or 0.003%, quantitative isolate recovery in treated animals was compared with that of untreated controls. A dose response was observed for all five susceptible strains. The two strains that were most sensitive to amphotericin B in vitro also were the most susceptible in vivo. At each dose level there was a two- to eightfold reduction in isolate recovery among highly susceptible strains compared with less susceptible strains (P less than 0.05). The five resistant strains remained so even when the 0.3% concentration was used. Among strains of C. albicans susceptible to amphotericin B, there appeared to be a variation in degree of susceptibility in vivo that correlated with the minimum inhibitory concentration.