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. Lesions are more severe in immunocompromised hosts. In addition, rats inapparently infected during nonsterile surgical procedures are less active in open-field testing. Infected rats have alterations in the fibrinogen level in plasma, the glucose level in serum, total leukocyte counts, and wound histology scores. The hallmark of S. aureus infection is suppurative inflammation, with abscess formation in virtually any organ.