The fate of individual organisms during clearance of experimental cutaneous Candida albicans infections in mice.

Abstract

A mouse model of acute cutaneous Candida albicans infections was used to study the manner in which these infections are cleared. Results of histological examination were correlated with determinations of the viability by acridine orange staining of superficial C. albicans pseudohyphae retrieved from the surface of the infected skin. The number of organisms retrieved from the skin surface was highest on the third and fourth day after inoculation, a finding which appeared to relate to a loss of Candida foci observed histologically to occur after the second day. Viability was high (approximately 80%) for at least 1-2 days after the organisms were seen histologically to have become associated with neutrophils and extruded from the stratum Malpighi into the stratum corneum; however, at later time points (fourth and fifth day after inoculation), the viability of the retrieved organisms did decline. Pseudohyphae germinated in vitro and applied to the skin of mice were found to be non-viable when retrieved 24 h later. These data suggest that the microbicidal processes of neutrophils may not be required for resolution of these infections. They are most consistent with clearance through an epidermal proliferative response which relocates the infecting organisms to a very superficial site, from which they can be either lost in a viable state, or subjected to killing by other factors at the skin surface.