The genus Ureaplasma contains a single species, U. urealyticum, of which some 14 serotypes have been described. Ureaplasma is distinguished from Mycoplasma by its production of urease. On special Ureaplasma agar media, colonies are small and circular and grow downward into the agar. In liquid media containing urea and phenol red, growth of Ureaplasma results in production of ammonia from the urea, with a resultant increase in pH and a change in color of the indicator.
The main reservoir of human strains of U. urealyticum is the genital tract of sexually ac-tive men and women; it is rarely found before puberty. Colonization, which probably re-sults primarily from sexual contact, occurs in more than 80% of individuals who have had three or more sexual partners.
Because of the high colonization rate, it has been difficult to associate specific illness with Ureaplasma; however, studies suggest that approximately one half of cases of non- gonococcal, nonchlamydial urethritis in men may be caused by U. urealyticum. In Ureaplasma has been shown to cause chorioamnionitis and postpartum fever. The organism has been isolated from 10% of women with the latter syndrome.
Men with nongonococcal urethritis should be treated since Ureaplasma infection may be involved. Tetracycline is the treatment of choice because it is also active againstChlamydia, but tetracycline-resistant strains of Ureaplasma have been reported that have been associated with recurrences of nongonococcal urethritis in men. In such cases, spectinomycin treatment or treatment with quinolone antimicrobics is also effective. Women with postpartum fever due to U. urealyticum may respond to tetracycline treatment.