Experimental arthritis in mice with Mycoplasma pulmonis.

A Mycoplasma pulmonis strain, recovered from the arthritic joints of mice employed in the serial passage of a chemically induced tumor, was found to be arthritogenic for mice under experimental conditions. Some joint involvement occurred in all mice challenged intravenously with this strain, and M. pulmonis was recovered frequently from the enlarged joints. The arthritis was migratory, appearing first in the radiocarpal joints and later in the tibiotarsal joints. There was little evidence of a generalized mycoplasmal infection as a consequence of the experimental challenge. Histopathologically, the early stages of the infection in the joints was characterized by an inflammatory response in the synovium and periarticular tissues. Exudate in the joint space contained about equal numbers of polymorphonuclear and mononuclear cells. The polyarthritis resolved slowly, but some residual joint enlargement was noted for as long as 4 months. Two other M. pulmonis strains were also observed to be arthritogenic for mice. Rats were not susceptible to M. pulmonis challenge. Characteristics of the nonsuppurative M. pulmonis arthritis in mice were compared to M. arthritidis joint infections in rats.