| Genital tract infections have long been recognized as one of the important causes of male infertility. In all kinds of pathogens, Ureaplasma urealyticum (UU) infection in the genital tract is revealed widespread in human population. UU has a higher detection rate in infertile people than in fertile people. Detection rate of UU fluctuates between 10-70% in different population and is increasing gradually in recent years. The role of UU infection in the etiology of poor semen quality is still controversial up to now. Although in some population surveys and experimental studies, it has been revealed that men with UU infection in their genital tracts have a declined semen quality, the evidence from well-designed epidemiology is still not enough.This study was designed as a cross-sectional epidemiological survey, combined with experimental methods. Two hospitals in Shanghai were chosen as study fields and 346 eligible patients were consecutively enrolled as subjects. The semen qualities of the eligible subjects were analyzed in order to assess the fertility. By semen UU cultivation it was found 136 subjects were UU positive and 210 subjects were UU negative. All subjects accepted external genital tract examination and semen analysis. The demographical characteristics and other related information were collected by constructed questionnaire investigation. Influence factors associated with UU infection and semen quality were explored. The relationships between UU infection and semen quality (semen volume, sperm concentration, sperm motility, sperm morphology, sperm viability, etc.) were analyzed thoroughly. The statistical methods applied in this study include: χ2 test (general association, CMH, trend), general linear model, mixed linear model, analysis of covariance, factorial analysis, multiple linear regression, logistic regression (uni- and multiple non-conditional Logistic, ordered-response logistic), and principal component analysis.UU infection of the male genital tract could negatively affect seminal plasma characteristic. The proportion of higher semen viscosity in men with UU infection (12.50%) was significantly higher than that in men without UU infection (4.76%)(P<0.01). Mean semen pH value was 7.17 and 7.23 in UUpositive and negative respectively, and the difference was significant(P<0.03). The proportion of lower pH value (<7.2) in UU positive subjects (41.91%) was significantly higher than the proportion in UU negative subjects (27.88%)(P<0.01).The semen volume was 3.17 mL in men with UU infection, and 3.42 mL in men without UU infection, but the difference was not significant. The proportion of semen volume below 2mL in UU positive subjects (11.76%) was slightly higher than the proportion in UU negative subjects (8.13%) (P=0.26). However, it was found that history of spermatorrhoea could interact with the effect of UU infection. Among the subjects without sex development history of spermatorrhoea, semen volume in subjects with UU infection (1.92 mL) was significantly lower than that in subjects without UU infection (3.57 mL) (P<0.01). UU infection could negatively affect sperm concentration and total sperm counts. The two indexes above were 54.04×106/mL and 161.41×106 in subjects with UU infection, respectively. However, sperm concentration and total sperm counts were 70.58×106/mL and 230.03×106 in subjects without UU infection respectively. It was shown that male genital tract UU infection was associated with declined sperm counts(P<0.01). Results from trend χ2 analysis showed sperm concentration inclined to lower level in subjects with UU infection. Although the proportion of oligospermia in subjects with UU infection was not significantly higher than that in subjects without UU infection, the OR of subfertile status (sperm concentration < 40×106/mL) was 1.70 (95%CI 1.08-2.68) in the former when compared with the latter. The above results were supported by multiple-variate analyses.The proportions of teratospermia were 9.52% in UU positive subjects and 5.29% in U...
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