Pathogenicity of Trichosporon asahii in a murine model of disseminated trichosporonosis

Abstract

Background: In recent years, superficial and deep mycoses caused by trichosporon were occasionally reported. In 2001, we reported the first case of disseminated trichosporonosis caused by Trichosporon asahii (T. asahii) in China. In this study, the pathogenicity of T. asahii was investigated in a murine model of disseminated trichosporonosis.

Methods: Seventy-five mice were randomly divided into 7 groups. Each group was inoculated with T. asahii, through intradermal, gastrointestinal tract or intravenous injection. The mice in the experimental groups were given an intraperitoneal injection of cyclophosphamide (CY) to induce granulocytopenia. Mice in the therapeutic group were given both liposomal amphotericin B and fluconazole. The main viscera of the mice were examined by means of tissue culture and pathologic sections.

Results: In the two intravenous inoculation groups, T. asahii was isolated from at least one organ in 10 of the 12 granulocytopenic mice and 2 of the 14 immunocompetent mice. Two of the 7 mice in the granulocytopenia group presented with lesions in the inoculation position, but none of the 30 mice in the granulocytopenia and the control group which were inoculated intradermally or through the gastrointestinal tract had viscera infection. In the therapeutic group, the ratio of consequently dead mice, the number of involved viscera, and the incidence of systemic infection were significantly less than the untreated group. Acute purulent inflammation and granulomatous inflammation were the main pathological changes in the course of the infection. Arthrospores and filaments were found in the focus.

Conclusions: T. asahii is an opportunistic pathogen that causes cutaneous and visceral infections in immunologically impaired hosts. An immunocompetent host was to be infected by the invading T. asahii. Several organs, namely the liver, lungs, kidneys, spleen and heart, were predisposed. The therapy of combining liposomal amphotericin B with fluconazole can prevent the host from an infection and inhibit the diffusion of the infection.