Sporothrix brasiliensis Treatment Failure without Initial Elevated Itraconazole MICs in Felids at Border of Brazil

Cat-transmitted sporotrichosis caused by Sporothrix brasiliensis is an emerging zoonosis in Latin America. Because treatment of feline sporotrichosis is often not effective, we sought to determine whether treatment failure results from S. brasiliensis strains that have existing elevated MICs for itraconazole, the primary treatment for this disease. During 2021–2023 at the triple border region of Brazil, Paraguay, and Argentina, 108 S. brasiliensis strains were isolated from felines before antifungal treatment. The main clinical manifestation was cutaneous disseminated sporotrichosis (61%), which was the only form resulting in sporotrichosis-induced deaths (61%). We conducted antifungal susceptibility testing for 9 antifungal compounds, evaluating for both mycelial and yeast phases. MIC levels were low for most antifungal agents but were higher in the mycelial phase than in the yeast phase, especially for voriconazole and isavuconazole. We conclude that the varying clinical manifestations of sporotrichosis and large differences in mortality rates were not caused by elevated itraconazole MICs.