Septic arthritis due to Pasteurella multocida complicating rheumatoid arthritis.

A patient with rheumatoid arthritis treated with corticosteroids developed a septic arthritis of her right knee. She had been bitten on her right leg by her pet cat 2 weeks earlier. Pasteurella multocida, resistant to penicillin, was isolated from the septic joint and from the oropharynx of the cat. The arthritis was successfully treated with ampicillin. No attempt to eradicate the organism from the cat was made because of the expectation of early recolonisation.