Different virulence levels of the species of Sporothrix in a murine model

A comparative study on the experimental pathogenicity of five species of Sporothrix of clinical interest, Sporothrix albicans, Sporothrix brasiliensis, Sporothrix globosa, Sporothrix mexicana, and Sporothrix schenckii sensu stricto, was performed using an immunocompetent murine model. Two strains of each species and two levels of inoculum for each strain (2 × 107 and 2 × 104 conidia/animal) were tested by intravenous inoculation of mice (ten per group). Mortality was caused by the low inoculum of one strain of S. brasiliensis only, and the high inocula of S. brasiliensis and S. schenckii strains. Other inocula and other species tested did not kill any of the experimental animals. Tissue burden studies showed fungal spread to kidneys, lungs, spleen, brain, and testicles. S. brasiliensis was recovered extensively from all of the studied organs, and S. schenckii and S. globosa were recovered in lower amounts. Histopathological studies revealed differences in the lesions, which ranged from local inflammation with a low number of fungal cells at the injection site in mice infected with S. globosa, to massive infiltration of fungal cells in organs of those infected with S. brasiliensis. Our findings showed that S. brasiliensis and S. schenckii were the most virulent species, and suggest that lesional mechanisms could be species-specific.