Survival in experimental Candida albicans infections depends on inoculum growth conditions as well as animal host

Evidence is presented that the growth medium used to prepare a Candida albi cans challenge inoculum is a significant factor determining the ability of a fungus strain to gain an initial invasive hold immediately after injectio n into an animal host, and thus determining gross strain lethality. Three C . albicans strains, one known to be attenuated in virulence, were grown in two broth media and injected intravenously at different doses into female N MRI mice and male albino guinea pigs. For each fungus strain and challenge dose, survival was longer from inocula grown in a diluted, buffered peptone -based broth than from inocula grown in Sabouraud glucose broth. When anima ls were challenged intravenously with yeast doses adjusted to give the same mean survival time regardless of strain or growth medium, the progression of fungus tissue burdens (c.f.u. g(-1)) in kidneys, lungs, liver, spleen an d brain samples was broadly similar for all three C. albicans strains but d iffered between the two animal hosts. The morphological form of C. albicans recovered from infected tissues differed at the level of both the fungus s train and the host tissue. Use of survival-standardized inocula provides a means of distinguishing differences in progression of experimental dissemin ated Candida infections that are related to the infecting strain from those related to the animal host.