Experimental murine model of disseminated Pseudallescheria infection

Abstract

Pseudallescheria boydii is found in soil and has a worldwide distribution. This fungus was initially identified as a pathogen targeting a variety of tissues. There are fragmentary data in the literature on the in vitro susceptibility of P. boydii to different antifungal compounds. P. boydii is highly refractory to antifungal treatments. In this study, a murine model of disseminated Pseudallescheria infection was developed to evaluate efficacy of different treatment regimens. A clinical strain of P. boydii was studied in normal and neutropenic outbred ICR mice. Several inocula were tested over a range from 1 × 103 to 5 × 106 cfu. Groups of eight mice were injected with a intravenous dose of one inoculum. Mortality correlated with the dose of the inoculum, and with immunosuppression. Quantitative cultures of various tissues showed initial dissemination of disease in immune competent mice. This was followed by reduction of tissue burden, except in the brain. In contrast, disseminated infection persisted in most organs in immunosuppressed animals (p < 0.0001). This model should be appropriate for in vivo evaluation of antifungal chemotherapy.