Variation in the lethal response in mice to yeast-like and pseudohyphal forms of Candida albicans.

The lethal response in mice to yeast-like cells of Candida albicans grown for 3, 6, or 9 h in a defined minimal culture medium was more severe than that observed with corresponding pseudohyphal preparations. This differential effect could be only partially correlated with the greater number of viable units in respective yeast-like cultures. No significant differences between yeast-like and pseudohyphal syspensions were detected when turbidity-mass ratios were examined. The injection of physiological saline suspensions containing increasing quantities of yeast-like cells resulted in proportional decreases in mouse survival times. Conversely, when comparable experiments were conducted with pseudohyphal preparations no significant decreases in survival times occurred. The data indicate that these differences in the lethal response cannot be explained solely on the basis of a variation in the number of viable units or cell mass in corresponding yeast-like and pseudohyphal preparations. Factors contributing to this phenomenon may therefore include altered susceptibilities to host defense mechanisms in the early stages of the infectious process as a result of differences between these yeast-like and pseudohyphal inocula.