Comparison of Isolates of Sporothrix schenckii Obtained from Fixed Cutaneous Lesions with Isolates from Other Types of Lesions

Thirty-four clinical isolates of Sporothrix schenckii were studied for their temperature sensitivity and morphology in vitro. Four selected isolates were also studied for their morphology and growth rate in vivo. Conidia from 26 clinical isolates obtained from lymphocutaneous or extracutaneous lesions formed colonies at both 35 C and 37 C in vitro within five days. Conidia from eight isolates obtained from fixed cutaneous lesions (nonlymphangitic) formed colonies at 35 C but failed to do so at 37 C during a two-week incubation period. Studies of the growth rate at 25 C and morphology in vitro did not show any clear differences between the two groups of isolates. When the isolates that grew at 37 C were injected into mice by the intraperitoneal route, the organisms multiplied well in the internal organs but multiplied even better in the testes. Mice developed skin lesions on paws and tails within 72 days after injection. When the isolates that did not grow at 37 C were injected into mice by the same route, the organisms did not multiply in the internal organs but grew well in the testes. These mice did not develop any skin lesions during the 72day observation period. Epidermal or intradermal inoculation of conidia into guinea pigs showed that the isolates capable of growth at 37 C produced skin lesions with a lower concentration of conidia than the isolates not growing at 37 C. Of four additional isolates from natural sources, three grew at 37 C in vitro.