Feline Dermatophytic Pseudomycetoma (Microsporum canis) Infection with Actinobactoer ursingii in a British Shorthair Cat: A Case Report in Thailand

Dermatophytic pseudomycetoma is a rare, invasive fungal infection characterized by deep dermal and subcutaneous involvement of dermatophytes, uncommonly reported in cats. A 10-month-old, 2.8 kg, sexually intact female British Shorthair cat presented to a veterinary clinic with multiple abscessed nodules on the body, legs, and tail. Lesions contained yellow purulent discharge with granular material resembling fungal grains. Hematological and biochemical analyses revealed values within normal reference ranges. Bacterial culture and antimicrobial susceptibility testing identified Acinetobacter ursingii. Histopathological examination of skin biopsy revealed multifocal to coalescing granulomatous inflammation within fibrotic dermis. Granulomas contained central necrosis with large arthroconidia morphologically consistent with Microsporum canis. Fungal culture remained negative after 14 days of incubation. The cat was treated with surgical excision of nodular lesions, followed by oral antifungal (itraconazole) and antimicrobial therapy. No recurrence of pseudomycetoma was observed during a two-month follow-up period. This case report highlights the clinical, histopathological, and microbiological features of rare M. canis-associated dermatophytic pseudomycetoma with concurrent A. ursingii infection in a cat in Thailand, emphasizing diagnostic challenges and successful management strategies.