Difference in the virulence of Ureaplasma urealyticum isolates.

The virulence of Ureaplasma urealyticum strains was tested by intrarenally infecting white mice of undefined, LATI (Gödöllö, Hungary) and BALB/c breed. Freshly isolated human strains differed in virulence; when subcultured in U-9 medium they showed a gradual loss of virulence. Ureaplasma strains of calf and swine origin were virulent to mice in a medium degree. Some of the inoculated mice showed the signs of latent infection.