The Prevalnece and Clinical Significance of Urethritis and Cervicitis in Asymptomatic People 705 had three different species, and 1 patient had four different species. The prevalences of Ureaplasma urealyticum and Myco- plasma hominis were 22.1% and 11.6%, respectively. In people who were infected with Chlamydia trachomatis, the prevalences of Ureaplasma urealyticum (35.0%) and Mycoplasma hominis (22.5%) were higher than in those not infected with Chlamydia trachomatis (Table 1, 2). DISCUSSION Chlamydia trachomatis infection is the most prevalent TABLE 1. Species isolated from an asymptomatic general popula- tion Species in 709 samples Free of microorganisms C. trachomatisa N. gonorrhoeaea M. genitaliuma U. urealyticuma M. hominisa T. vaginalisa Total no. Men (430) Women (279) 480 (67.7) 282 (65.6) 198 (71.0) 40 (5.6) 29 (6.7) 11 (3.9) 3 (0.4) 2 (0.5) 1 (0.4) 2 (0.3) 1 (0.2) 1 (0.4) 157 (22.1) 112 (26.0) 45 (16.1) 82 (11.6) 39 (9.1) 43 (15.4) 8 (1.1) 1 (0.2) 7 (1.0) Values are presented as number (%), a: regardless of the existence of other species TABLE 2. Samples containing clinical pathogens Combinations with C. trachomatis C. trachomatis only C. trachomatis+U. urealyticuma C. trachomatis+M. hominisa C. trachomatis+U. urealyticum+M. hominisa C. trachomatisb C. trachomatis+N. gonorrhoeaea C. trachomatis+M. genitalium+U. urealyticum+M. hominis C. trachomatis+U. urealyticumc C. trachomatis+M. hominisc Combinations with N. gonorrhoeae N. gonorrhoeae only N. gonorrhoeae+C. trachomatis Combinations with M. genitalium M. genitalium+U. Urealyticum+M. hominis M. genitalium+C. trachomatis+U. Urealyticum+M. hominis Combinations with T. vaginalis T. vaginalis only T. vaginalis+M. hominisa sexually transmitted bacterial infection among women and men worldwide. Chlamydia trachomatis is usually de- scribed as an obligate intracellular pathogen and accounts for 30% to 40% of the etiopathogenesis of urethritis [9]. However, about half of infected subjects are asymptomatic. Thus, there are many silent infections in the community. Mason et al showed that the prevalence of Chlamydia tra- chomatis in asymptomatic men was 4% (14/349) [10]. Takahashi et al reported that Chlamydia trachomatis was detected in 6% of samples from healthy people [11]. Similarly, in our study, Chlamydia trachomatis was ob- served in 40 persons (5.6%). Unfortunately, it is usually not detected by routine microbiological diagnosis [1,12]. Thus, most asymptomatic patients are neglected unless they vis- it the clinic to be evaluated for STI by chance or face compli- cations such as pelvic inflammatory disease. Neisseria are fastidious Gram-negative cocci that re- quire nutrient supplementation to grow in laboratory cultures. Although gonorrhea can be diagnosed by in- spection of the yellowish discharge from the urethra, many patients infected with Neisseria gonorrhoeae have no discharge. Furthermore, it is known that 10% of infected males and 50% of infected females are asymptomatic. Hein et al studied 2672 sexually active adolescents and reported that prevalence rates of asymptomatic gonorrhea were 1.9% among boys and 7.0% among female adolescents [13]. Regardless of age group, a surveillance study reported prevalence rates of gonorrhea in healthy people of 0.06% Total no. (40) 22 (55.0) 7 (17.5) 2 (5.0) 6 (15.0) 37 (92.5) 2 (5.0) 1 (2.5) 14 (35.0) 9 (22.5) 1 (33.3) 2 (66.7) 1 (50.0) 1 (50.0) Total no. (3) Total no. (2) Total no. (8) 6 (75.0) 2 (25.0) Men (29) 18 (62.1) 4 (13.8) 0 4 (13.8) 26 (90.0) 2 (6.9) 1 (3.4) 9 (31.0) 5 (17.2) Men (2) 0 2 (100) Men (1) 0 1 (100) Men (1) 0 1 (100) Women (11) 4 (36.4) 3 (27.3) 2 (18.2) 2 (18.2) 11 (100) 0 0 5 (45.5) 4 (36.4) Women (1) 1 (100) 0 Women (1) 1 (100) 0 Women (7) 6 (85.7) 1 (14.3) Values are presented as number (%), C. trachomatis: Chlamydia trachomatis, U. urealyticum: Ureaplasma urealyticum, M. hominis: Mycoplasma hominis, N. gonorrhoeae: Neisseria gonorrhoeae, M. genitalium: Mycoplasma genitalium, T. vaginalis: Trichomonas vagi- nalis, a: samples not containing other species, b: samples not containing other pathogens, regardless of the existence of commensal micro- organisms, c: regardless of the existence of other species Korean J Urol 2011;52:703-708