Biogenic Silver Nanoparticle: In vitro antifungal activity against Sporothrix brasiliensis

Sporothrix brasiliensis is the predominant etiological agent of feline sporotrichosis in Brazil, where zoonotic dissemination represents an escalating public health concern. Reports of therapeutic refractoriness and the emergence of itraconazole-resistant isolates underscore the pressing need for alternative antifungal strategies. This study evaluated in vitro antifungal activity of a biogenic silver nanoparticle against 24 Brazilian clinical isolates of S. brasiliensis (18 cats and 6 dogs). Broth microdilution assays revealed minimum inhibitory concentrations ranging from 0.47 to 3.75 µg/mL with fungicidal and fungistatic activity. Scanning electron microscopy of treated yeast cells demonstrated pronounced morphological alterations, including cell wall discontinuities, cavitations, surface roughness, and leakage of intracellular contents, confirming severe structural damage. These findings demonstrate that the biogenic silver nanoparticle evaluated exhibits antifungal activity against S. brasiliensis and may represent a promising therapeutic alternative for sporotrichosis. Nonetheless, further in vivo studies are needed to validate their safety and clinical applicability.