Normal, Diabetic, and Neutropenic Mice

Opportunistic infections caused by Candida tropicalis have been noted with increasing frequency in compromised patients. The pathogenicity of three isolates of C. tropicalis was studied in normal CD-1 mice, streptozotocin-induced diabetic mice, and cyclophosphamide-induced neutropenic mice. Lethal dose 50% endpoints and quantitative distribution of yeast cells in spleen, liver, and kidneys of mice infected intravenously were determined. The virulence of one yeast isolate was greater than that of the other two. The order of susceptibility to mortality and degree of organ colonization was neutropenic > diabetic > normal. Renal lesions resembling those associated with infection by C. albicans appeared by day 5 postinfection in diabetic and neutropenic mice. Greater numbers of C. tropicalis yeast cells were isolated from homogenates of the affected kidneys, suggesting that the kidney is a target organ for this fungus. This study demonstrates the increased susceptibility of compromised mice to C. tropicalis as compared with normal mice and verifies the ability of these yeasts to cause opportunistic disease.