Pasteurella multocida

Pasteurella multocida is a small, gram-negative, nonmotile, non–spore-forming coccobacillus with bipolar staining features. P multocida often exists as a commensal in the upper respiratory tracts of many livestock, poultry, and domestic pet species, especially cats and dogs. P multocida infection in humans is often associated with an animal bite, scratch, or lick, but infection without epidemiologic evidence of animal contact may occur.

Wound infections associated with animal bites usually have a polymicrobial etiology, mandating the empiric use of broad-spectrum antimicrobials targeted at both aerobic and anaerobic gram-negative bacteria. Nevertheless, Pasteurella species are commonly isolated pathogens in most animal bites, especially in dog- and cat-related injuries. These injuries can be aggressive, with skin manifestations typically appearing within 24 hours following a bite. These wounds can exhibit a rapidly progressive soft-tissue inflammation that may resemble group A β-hemolytic Streptococcus pyogenes infections.