CHARACTERISTIC INFECTIVITY OF SPOROTHRIX-SCHENCKII TO MICE DEPENDING ON ROUTES OF INFECTION AND INHERENT FUNGAL PATHOGENICITY

Isolates of Sporothrix schenckii were examined for their infectivity i n BALB/c mice. The mice were injected with yeast forms of S. schenckii isolates differing in clinical source (human cutaneous lesions and pu lmonary lesions), and fungal growth was determined at intervals in the footpad and visceral organs. After subcutaneous injection of approxim ate to 10 colony forming units (cfu) of S. schenckii into the footpad, locally restricted fungal infection developed gradually. At the peak of the infection (3-4 weeks post-inoculation), viable fungal counts re ached 10(2)-10(6) cfu/footpad. Dissemination to other tissues and visc eral organs was not observed. After intravenous or intraperitoneal inj ection of 10(6) cfu of yeast forms, three of four isolates from cutane ous sporotrichosis were unable to establish infection and were elimina ted from blood and visceral organs. The development of systemic infect ion was observed only with S. schenckii isolates obtained from the hum an lung lesion. Thus, inherent properties of each clinical isolate and routes of infection were shown to be critical for the establishment o f systemic infection in spite of the remarkably strong infectivity of S. schenckii to the cutaneous tissue.