Abstract: In this paper, a 13-year-old cat was treated in a pet hospital. The deep cavity in the extraction part of the left maxillary canine teeth was washed with sterilized saline, which could flow out from the nostril and the inner corner of the eye. A large number of cheese-like substances rushed out from the left nostril. The diagnosis of the cat’s mouth-nostril fistula was made. Blood cell, blood biochemistry, blood gas ion analysis and drug sensitivity test were carried out, and systemic drug treatment and local debridement were carried out for a week. The results showed that the leucocyte count was 29.2×10⁹/L, which was significantly higher than the reference value, and the blood sugar was 20.93 mmol/L, which was significantly higher than the reference value, suggesting that the wound of the cat in this case was not conducive to healing. Bacterial culture and strains were identified as Escherichia coli. Drug susceptibility tests showed that it was resistant to most antibiotics such as penicillins, cephalosporins and quinolones, and sensitive to carbapenems. The cat was debrided and meropenem was injected intravenously at a dose of 24 mg/kg. After 3 days of infusion treatment, the cat’s mental state improved. After 5 days, the cat could eat independently. After 7 days, the infusion was stopped and the fistula was washed every day until the 24^th day.

Key words: old cat, oronasal fistula, diagnosis, debridement, treatment