Junichi Tokunaga

Germ tube-forming cells of Candida albicans are more susceptible to clotrimazole-induced killing than yeast cells

Yeast and germ tube-forming cells of Candida albicans were compared with respect to their susceptibility to killing induced by the imidazole antifungal clotrimazole. Cultures consisting largely of germ tube-forming cells or exclusively yeast cells were prepared by incubating cells of a germ tube-proficient strain in a proline-containing phosphate buffer at 37 degrees C or 25 degrees C, respectively. When treated with clotrimazole at 37 degrees C, the cultures of germ tube cells lost colony-forming ability much more rapidly than those of yeast cells. However, this difference was diminished in the cells preincubated at 37 degrees C but prevented from forming germ tubes by 5 mM cysteine, a suppressor of germ tube formation. In another C. albicans isolate showing a very poor capacity to form germ tubes at 37 degrees C, such a difference in killing rate was much smaller than that for the germ tube-proficient strain. Furthermore, when an isogenic pair of strains, one proficient and the other deficient in germ tube formation, were compared with each other, germ tube-forming cultures of the former were found to be more sensitive than yeast cell cultures of the latter. It is inferred from these results that the germ tube-forming cell of C. albicans is more sensitive to clotrimazole-induced killing than the yeast cell.