IN OVO PATHOGENICITY OF MYCOPLASMA INERS STRAIN OZ

Embryonating chicken eggs were inoculated with the ripe strain (PG30) of Mycoplasma iners and with an additional strain of this species desi gnated Oz, Marked gross and histopathologic lesions were observed in t he embryos inoculated with strain Oz but not in those infected with st rain PG30. Gross lesions were manifested by an enlargement of one or m ore joints that often contained a caseous exudate, both in the joint s pace and periarticularly In the order of frequency, the most common le sions were found in the following joints: tibiotarsal, distal humoral, proximal humoral, femoral, mandibular, tibiofemoral, and phalangial. Similar caseous foci were also seen in the liver and, rarely, in the h eart, Histologically, the most prominent lesion found in the joints an d viscera was a multifocal caseous necrosis accompanied by the formati on of granulomas. Many joints had progression of the inflammatory cell s outward from the joint spaces along the periosteal surfaces, and the articular cartilages contained erosions and focal necrosis.