Septic arthritis due to Pasteurella multocida.

We have reported two cases of septic arthritis caused by Pasteurella multocida, the first, septic polyarthritis unrelated to animal contact and the other, septic monarthritis after a cat scratch. Serious infections with this gram-negative bacillus must be treated with intravenous penicillin, ampicillin, or a third-generation cephalosporin; aminoglycosides are not effective. A high index of suspicion is appropriate when there is a history of a recent animal-inflicted wound, though infection may also occur with either nontraumatic animal contact or no recognized animal contact at all.