Characteristic infectivity ofSporothrix schenckiito mice depending on routes of infection and inherent fungal pathogenicity

Abstract

Isolates of Sporothrix schenckii were examined for their infectivity in BALB/c mice. The mice were injected with yeast forms of S. schenckii isolates differing in clinical source (human cutaneous lesions and pulmonary lesions), and fungal growth was determined at intervals in the footpad and visceral organs. After subcutaneous injection of ≈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 reached 10²–10⁶ cfu/footpad. Dissemination to othertissues and visceral organs was not observed. After intravenous or intraperitoneal injection of 10⁶ cfu of yeast forms, three of four isolates from cutaneous sporotrichosis were unable to establish infection and were eliminated from blood and visceral organs. The development of systemic infection was observed only with S. schenckii isolates obtained from the human lung lesion. Thus, inherent properties of each clinical isolate and routes of infection were shown to be critical for the establishment of systemic infection in spite of the remarkably strong infectivity of S. schenckii to the cutaneous tissue.