Differential association of ureaplasma species with non-gonococcal urethritis in heterosexual men

OBJECTIVE: To assess the role of Ureaplasma urealyticum and Ureaplasma parvum in patients with non-gonococcal urethritis (NGU) using specimens from a previously reported study of NGU. METHODS: Species-specific PCR assays for U urealyticum and U parvum were used to detect these organisms in specimens from men enrolled in a case-control study based in a Seattle STD clinic in order to evaluate their association with NGU. Urethritis was defined by clinical examination and the presence of inflammation on Gram stained smear. Controls had normal examination findings and no evidence of inflammation on Gram stain smear or by the leucocyte esterase test. RESULTS: U urealyticum was detected in 26% (31/119) of cases and 16% (19/117) of controls, resulting in an association with NGU (adjusted odds ratio (aOR)=2.3, 95% CI 1.04 to 4.9) after adjusting for age, race, history of prior urethritis and other NGU pathogens (Chlamydia trachomatis, Mycoplasma genitalium). The association of U urealyticum and NGU was strongest in white men <28 years of age (OR=5.4, 95% CI 1.3 to 22.2). U parvum was detected in 14% (17/119) cases and 31% (36/117 controls) and thus was negatively associated with NGU (aOR=0.4, 95% CI 0.2 to 0.8). The prevalence of U urealyticum (16%) in controls was higher than that of C trachomatis (3.4%) or M genitalium (4.3%, p<0.05, each comparison). CONCLUSIONS: Unlike U parvum, U urealyticum was associated with urethritis. The strong effect in younger white men and high rates in controls may suggest variability in virulence among U urealyticum strains or in host innate or acquired immunity.