Microflora of the urethra in adolescent boys: relationships to sexual activity and nongonococcal urethritis.

Urethral cultures were obtained from 90 adolescent youth, 16 of whom denied previous sexual activity. Among the sexually active boys was a group of 32 with clinically significant pyuria, consistent with the diagnosis of urethritis, on a first-part urinalysis (FPU) specimen. To relate differences in urethral microflora to sexual activity, 42 sexually active patients with a negative FPU were compared with the never sexually active group. The profile of anaerobic, but not aerobic, bacteria isolated from the urethra was related to the presence or absence of previous sexual activity. Mycoplasma species and Ureaplasma urealyticum were isolated from sexually active patients only, and may be markers of sexual activity in adolescent boys. Of the 32 patients with FPU evidence of urethritis, 22 (69%) had cultures positive for Chlamydia trachomatis, and an additional three (9%) had cultures positive for Neisseria gonorrhoeae. The findings in sexually active patients with a positive FPU were otherwise similar to those of sexually active patients without evidence of urethritis. C. trachomatis appears to be the most important agent of urethritis among adolescent boys with a positive FPU.