Enzootic Pneumonia in Pigs: Propagation of a Causative Mycoplasma in Cell Cultures and in Artificial Medium

Three strains of a new species of mycoplasma were recovered from pneumonic pig lungs, known free of Mycoplasma hyorhinis, by prolonged incubation in pig testicle cell cultures. The three strains produced a characteristic cytopathic effect in the cell cultures. A highly enriched meat-infusion-broth medium was evolved and permitted regular propagation of these organisms. Pneumonia could consistently be produced by intratracheal inoculation of pigs with the mycoplasma propagated in the enriched broth medium or in cell cultures. The mycoplasma were recovered from the lungs of experimentally infected pigs by inoculation into the broth medium. Comparative studies of the pneumonia producing mycoplasma and of M. hyorhinis were carried out in cell cultures, broth media, and in pigs infected experimentally by different routes. The morphological characteristics of the mycoplasma, grown in the different media, are described and illustrated.