Use of a mouse model to evaluate clinical and environmental isolates of Sporothrix spp. from the largest U.S. epidemic of sporotrichosis

Abstract

Five clinical and 69 environmental isolates from the largest U.S. epidemic of sporotrichosis were evaluated in NYLAR male mice following intravenous injection of 5 x 106 to 2 x 108 conidia per mouse. The clinical isolates and eight environmental isolates produced 100% mortality in groups of three mice each between 12 and 24 days after injection. These virulent isolates grew at 37°C, were dematiaceous by virtue of melanin (melanized) ion permissive media (e.g., potato dextrose agar), produced ovoid conidia borne sympodially on lateral conidiophores and pleurogenously about the main hyphal axis, and were identified as Sporothrix schenckii. Two melanized environmental isolates that grew at 35°C but not at 37°C were not virulent and had subtle morphological differences from S. schenckii. The remaining environmental isolates were not melanized, were not virulent, and were not S. schenckii; five were identified as Ophiostoma stenoceras and the remainder were identified as Sporothrix spp. Quantitative organ cultures revealed that clinical isolates grew exponentially in livers and testes, in contrast to an isolate of O. stenoceras that was eliminated from liver, lung, and spleen but that persisted in the testes throughout the 14-day sample period. This model helped to confirm the identification of S. schenckii isolates obtained from the environment.