Disease
P. multocida causes wound infections associated with cat and dog bites.
Important Properties
P. multocida is a short, encapsulated gram-negative rod that exhibits bipolar staining.
Pathogenesis & Epidemiology
The organism is part of the normal flora in the mouths of many animals, particularly domestic cats and dogs, and is transmit ted by biting. About 25% of animal bites become infected with the organism, with sutures acting as a predisposing factor to infection. Most bite infections are polymicrobial, with a variety of facultative anaerobes, especially Streptococcus species, and anaerobic organisms present in addition to P. multocida. Pathogenesis is not well understood, except that the capsule is a virulence factor and endotoxin is present in the cell wall. No exotoxins are made.
Clinical Findings
A rapidly spreading cellulitis at the site of an animal bite is indicative of P. multocida infection. The incubation period is brief, usually less than 24 hours. Osteomyelitis can complicate cat bites in particular, because cats’ sharp, pointed teeth can implant the organism under the periosteum.
Laboratory Diagnosis
The diagnosis is made by finding the organism in a culture of a sample from the wound site.
Treatment & Prevention
Penicillin G is the treatment of choice. There is no significant antibiotic resistance. People who have been bitten by a cat should be given ampicillin to prevent P. multocida infection. Animal bites, especially cat bites, should not be sutured. There is no vaccine.
