The objective is to estimate the efficacy of tinidazole for the treatment of Mycoplasma genitalium (MG) among male patients who have been diagnosed with non-gonococcal urethritis (NGU) at the Public Health - Seattle &King County (PHSKC) Sexual Health Clinic (SHC). Tinidazole was approved by the Food and Drug Administration (FDA) in May 2004 to treat other infections (i.e., trichomoniasis, giardiasis, amebiasis, bacterial vaginosis) but has not been systematically tested for effectiveness against M. genitalium. The dosing that the investigators are proposing does not significantly increase the risk associated with taking tinidazole and this investigation meets criteria for an IND exemption.

To estimate the efficacy of tinidazole for treating M. genitalium among people male sex at birth (men) diagnosed with NGU, the investigators will enroll men with NGU attending an urban sexual health clinic who have a positive test for M. genitalium. Prior to enrollment, men with NGU will have received syndromic therapy for NGU consisting of doxycycline 100mg orally twice daily for 7 days. After enrollment men with NGU will receive tinidazole 2 grams orally on day one followed by 500mg orally twice daily on days 2-10. Participants will undergo a test of cure 21 days after completing the tinidazole regimen to determine whether M. genitalium has been eradicated (microbiologic cure). Remnant urine specimens from the NGU diagnosis visit will be used to perform culture and minimum inhibitory concentration (MIC) assessment, and will undergo quantitative PCR (qPCR) to determine initial organism load. Urine specimens collected at the initiation of tinidazole therapy and at the test of cure will also undergo culture, MIC assessment, and qPCR .

Inclusion Criteria:

• ≥18 years of age
• Clinical diagnosis of NGU
• Urogenital MG documented by a positive NAAT in the prior 7 days
• Fluent in English
• Assigned male at birth
• Attending the PHSKC SHC
• Able to provide informed consent
• Able to undergo a test of cure (TOC) 21 days after completing the tinidazole regimen

Exclusion Criteria:

• Known allergy to tinidazole
• Other contraindications to tinidazole
• At the clinician's discretion

The investigators will adhere to sponsor reporting requirements for IPD. The investigators will share anonymized data to qualified investigators who request it upon IRB approval. The investigators will have the University of Washington IRB review other requests for sharing IPD.