P. pneumotropica is a gram-negative, nonhemolytic bacterium. While most species of rodents may harbor the organism, reports of natural outbreaks are rare and are generally limited to rats and immunocompromised mice. P. pneumotropica was isolated from infected otic bullae. However, in that report the primary pathogen was not clearly established. P. pneumotropica is frequently isolated from several sites on and within healthy rats and mice and is therefore considered an opportunistic pathogen.
Transmission is probably via direct contact and fomites.
Clinical disease, when apparent, is generally limited to lesions of the skin and adnexal structures, although ophthalmitis, conjunctivitis, and mastitis have also been reported. Lesions are characterized by suppurative inflammation. Natural infection of rats with P. pneumotropica could compromise research involving the skin. Transmission is direct, and entry into the body is via breaks in normal barriers. A variety of clinical presentations have been reported in rats and mice.