Abstract: Objectives To investigate the infection and colonization of Mycoplasma genitalium and Ureaplasma urealyticum in different male populations, to explore the association of M. genitalium and U. urealyticum with nongonococcal urethritis (NGU) respectively. Methods A case-controlled, cross sectional study of four different male populations was performed, namely:NGU patients (G1), non-NGU subjects attending STD clinic (G2), men who had sex with men participating in a health education program (G3), and healthy volunteers (G4). Nested PCR and culture were used to detect U. urealyticum. Nested PCR and PCR product sequencing were applied to detect M. genitalium. Results The prevalence rates of M. genitalium in the four study populations were 25.0%(25/100), 6.4%(6/94), 5.5%(6/110) and 0% respectively. Significant difference was found between each two groups except G2～G3 with apvalue of 0.80. By multivariate regression analysis, controlling for the age of first sex, new sexual partners, urethritis and condom use in the previous 3 months, M. genitalium was only associated with urethritis (P=0.004, OR=6.754, 95% CI 1.833～24.893). The direct sequencing of PCR products showed gene mutations, in comparison with the reference sequence in GenBank, in 3 samples. The prevalence rates of U. urealyticum by PCR in 4 groups were 40.0%, 44.7%, 22.7% and 46.9% respectively, and there was no significant difference between G1～G2, G1～G4 or G2～G4 with apvalue of 0.419, 0.325, 0.868 respectively, but the prevalence rate of U. urealyticum in G3 was significantly lower than that in other groups. Conclusions M. genitalium is strongly associated with NGU and the prevalence rate is significantly higher in groups with high risk sexual behaviors than that in general population. There is no association between the colonization of U. urealyticum and NGU.

Key words: Mycoplasma, Urealasma urealyticum, Urethritis, Homosexuality, male