A chronic chromoblastomycosis model by Fonsecaea monophora in Wistar rat.

Chromoblastomycosis is a chronic, cutaneous and subcutaneous infection characterized by verrucose lesions. It is primarily caused by Fonsecaea monophora in southern China and responds poorly to available therapies. In order to investigate the pathogenicity of Fonsecaea monophora, we established a chronic chromoblastomycosis animal model in Wistar rats. Suspensions of 2x10(6) cfu conidia and hyphal fragments were intracutaneous (ic) and subcutaneous (sc) on either side of the backs of the rats. Small nodules were formed at the inoculation sites within the first week after inoculation. By the second week, the nodules had enlarged and become soft, and pus could be aspirated from them. In the fourth week, the nodules in the ic inoculated group had ulcerated and sclerotic bodies were observed in smears prepared from all animals. In the 3rd month after inoculation, the nodules at the sites of the ic inoculation had become flat, with a thin black crust on the surface. For the ic inoculated group, sequential biopsy studies revealed extensive necrosis with neutrophil infiltration and sclerotic bodies and some debris of fungi in the 1st month, sclerotic bodies inside multinucleated giant cells by the 2nd month and widespread granulomatous inflammations in the 3rd month.