Feline Cutaneous Mycobacteriosis Caused by Mycobacterium farcinogenes: The First Case Report from Asia.

A 4-year-old spayed female domestic shorthair cat was referred with history of 8 months of chronic, non-healing draining wounds on the left lateral thigh and left inguinal region. The initial lesions arose from a cat bite wound on the thigh and a concurrent inguinal subcutaneous mass, both of which had failed to respond to empirical antimicrobial therapy. Prior to referral, cytology of the inguinal mass suggested a spindle cell tumor; however, histopathology following surgical excision revealed severe necrotizing pyogranulomatous mastitis and dermatitis, with no evidence of neoplasia. At the initial referral visit, bacterial cultures from both lesions yielded Mycobacterium farcinogenes, identified via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The cat was treated with pradofloxacin, topical amikacin gel, and azithromycin despite in vitro resistance, resulting in complete clinical remission after 24 weeks without adverse effects. To our knowledge, this is the first reported case of feline cutaneous mycobacteriosis caused by M. farcinogenes in Asia. This case expands the limited veterinary literature on M. farcinogenes infection, highlights the diagnostic challenges of atypical mycobacterial infections, emphasizes the critical role of species-level identification, and demonstrates the efficacy of prolonged, multidrug therapy in managing chronic non-healing wounds in cats.