Association of lysogenic bacteriophage MAV1 with virulence of Mycoplasma arthritidis.

Mycoplasma arthritidis causes a severe polyarthritis under natural conditions in rats and under experimental conditions in both rats and mice. Although the disease itself has been extensively studied, M. arthritidis virulence factors remain uncharacterized. Comparison of relative arthritogenicity of 20 strains of M. arthritidis revealed that the strains tended to fall into two groups, a highly arthritogenic group, inducing maximum arthritis scores of > or = 11 in rats, and a low-virulence group, inducing maximum scores of < 6. Chromosomal DNA from the more highly arthritogenic strains possessed sequences that hybridized by Southern analysis with a probe prepared from lysogenic M. arthritidis bacteriophage MAV1, while DNA from low-virulence strains did not. One of the low-virulence strains, 158, was experimentally lysogenized with MAV1. Lysogenized 158 showed a significant increase in arthritogenicity over nonlysogenized 158. These data suggest that MAV1 carries a factor that is important in pathogenesis of M. arthritidis-induced arthritis of rats.