This study will only include participants recruited as part an NIH/NIDA funded study (U01 DA036267 PIs Gorbach and Shoptaw) - the mSTUDY. By design, half of the participants are HIV-positive and half are HIV-negative and other inclusion criteria for the mSTUDY are as follows:  At least 18 but not older than 45 years of age on day of consent Identified biologically male at birth Willing to return for follow-up study visits every 6 months as long as the study is ongoing and be available to return for all study visits, barring unforeseen circumstances Willing and able to provide written informed consent to take part in the study Willing and able to provide adequate information for locator purposes STI testing at each study visit (with reporting and treatment referral when indicated) Understands and agrees to local STI reporting requirements  If HIV-negative at screening, report unprotected anal intercourse with a male in the past 6 months  Additional inclusion criteria specific to this study are:  Currently enrolled in mSTUDY mSTUDY participants who have turned 45 since enrollment in mSTUDY continue to be eligible for inclusion in this study. Previously diagnosed with pharyngeal gonorrhea (while an mSTUDY participant)  Participants will be excluded from the study if:  Mouthwash use is contraindicated, for example because of allergies or those who may need to avoid the high alcohol content of mouthwash such as recovery alcoholics maintaining their sobriety They are unwilling to stop use of their current mouthwash during the 24-week study period