Concurrent Isolation of Mycobacterium kansasii and Mycobacterium tuberculosis From a Cat With Atopic Dermatitis and Chronic Gingivostomatitis: A Potential Zoonotic Risk

An approximately 8-year-old spayed female American Shorthair cat was evaluated over a 9-month period primarily for perioral pruritus. The cat had a history of feline atopic dermatitis and chronic gingivostomatitis, for which she had received long-term anti-inflammatory and immunosuppressive therapy (prednisolone and cyclosporine) at a previous clinic. Initially, perioral and periocular erythema progressed to nodular lesions around facial lesions, the mouth, eye, and ear, which were unresponsive to 9 months of medical treatment. Fine needle aspiration (FNA) of a perinasal mass revealed pyogranulomatous inflammation with numerous macrophages containing bacillary or filamentous bacteria. Histopathological examination of an auricular mass confirmed granulomatous dermatitis, identifying abundant acid-fast bacilli within epithelioid macrophages via Ziehl-Neelsen stain. Cultures from ulcerated perinasal lesions and nasal exudates on 3% Ogawa medium, followed by Whole Genome Sequencing (WGS), detected Klebsiella pneumoniae (K. pneumoniae) . Real-time PCR on the same samples identified Mycobacterium kansasii ( M. kansasii ) in all specimens, with one sample also co-detecting Mycobacterium tuberculosis (M. tuberculosis) . This report highlights the first documented case of co-infection with M. kansasii and M. tuberculosis in a diseased cat. Considering the known association of secondary K. pneumoniae infections in human mycobacterial patients, this case prompts further investigation into the complexities of feline mycobacterial infections involving K. pneumoniae .