Abstract
Marmosets, from which endogenous ureaplasmas had been eradicated by treatment with minocycline, were tested for susceptibility to infection by ureaplasmas from the genital and respiratory tracts of other animal species. They could be infected with ureaplasmas of human and simian origin, but were resistant to bovine and canine ureaplasmas. The results indicated that human, marmoset and squirrel-monkey ureaplasmas may form a biological subgroup, distinct from bovine and canine ureaplasmas, and that host range should not be ignored as a parameter for classification.