Mycoplasma Genitalium Antibiotic Susceptibility and Treatment (MEGA)

The purpose of this study is to find out which of 2 different antibiotics, doxycycline or azithromycin, works best against germs that may cause nongonococcal urethritis. Study participants will include approximately 1200 men, 16 years of age or older, attending a sexually transmitted diseases clinic in Seattle, Washington with clinical signs of urethral inflammation (>=5PMNs/HPF on a Gram-stained slide prepared from urethral exudates and/or a visible urethral discharge upon examination). Urine specimens will be collected and tested for Mycoplasma genitalium and Ureaplasmas. Each participant will receive a blinded packet of study medication. Participants will answer an enrollment questionnaire and will also receive a log to complete between visits to record information about treatment adherence, side effects, symptoms, and sexual activity. All subjects will be asked to return for evaluation 3 weeks after the initial clinic visit. Subjects who test positive for M. genitalium and/or Ureaplasmas at the initial clinic visit will also be asked to return for a third study visit, 6 weeks following the initial clinic visit. During follow-up visits, participants will answer a follow-up questionnaire and will be re-evaluated for signs of urethritis. Those who were initially positive for M. genitalium and/or Ureaplasmas will be re-tested for these organisms. Study participants with signs and/or symptoms of urethritis or who test positive for M. genitalium or Ureaplasmas at the follow-up study visit will receive another blinded treatment packet containing the alternate medication. Those who require additional treatment at the 6-week visit will be asked to return for a fourth follow-up study visit at 9-10 weeks. Study participants who did not test positive for M. genitalium or Ureaplasmas at the initial clinic visit, but who continue to demonstrate signs and/or symptoms of infection at their single follow-up study visit will treated according to clinic standard of care (after the study clinician unblinds their randomly-assigned treatment regimen).