Pasteurella are small Gram-negative coccobacilli that are primarily commensals or pathogens of animals. However, these organisms can cause a variety of infections in humans, usually as a result of cat scratches, or cat or dog bites or licks.
Pasteurella infections will be reviewed here. Other infections related to dog and cat bites or scratches are discussed separately. (See "Soft tissue infections due to dog and cat bites" and "Initial management of animal and human bites" and "Zoonoses from dogs" and "Zoonoses from cats".)
The members of the genus Pasteurella are small, nonmotile, nonspore-forming organisms. In Gram stained specimens, they generally appear as a single bacillus, often with bipolar staining, but may also be seen in pairs or short chains (picture 1) .
Pasteurella spp are aerobic, facultatively anaerobic, and grow well at 37ºC on 5 percent sheep blood (the preferred culture medium), chocolate, or Mueller-Hinton agar; growth is uncommon on MacConkey's agar. Most strains recovered from clinical specimens are catalase, oxidase, indole, sucrose, and decarboxylate ornithine positive. The indole-positive species exhibit a mouse-like odor. Media containing vancomycin, clindamycin, and/or amikacin have been used to select for pasteurellae . Potential bacterial virulence factors include capsule lipopolysaccharide, a cytotoxin, iron acquisition proteins, and other surface structures including homologues of the Bordetella pertussis filamentous hemagglutinin [2,3].
Human infections have been reported from P. multocida (the most common pathogen and type species for the genus), including P. multocida subsp multocida, P. multocida subsp septica, and P. multocida subsp gallicida; P. canis; P. dagmatis; and P. stomatis [4,5]. All except P. canis (associated only with dogs) are associated with dogs and cats. The subspecies of P. multocida can be differentiated by PCR fingerprinting . Related species include [P.] aerogenes, [P.] bettyae, [P.] caballi, [P.] pneumotropica, [P.] trehalosi, and [P.] haemolytica .