The Relationship Between Insertive Oral and Anal Sex and Select Measures of the Composition of the Urethral Microbiota Among Men Who Have Sex With Men.

BACKGROUND:Sexual behavior may influence the composition of the male urethral microbiota, but this hypothesis has not been tested in longitudinal studies of men who have sex with men (MSM). METHODS:From 12/2014-7/2018, we enrolled MSM with non-gonococcal urethritis (NGU) attending a sexual health clinic. Men attended five in-clinic visits at 3-week intervals, collected weekly urine specimens at home, and reported daily antibiotics and sexual activity on weekly diaries. We applied broad-range 16S rRNA gene sequencing to urine. We used generalized estimating equations to estimate the association between urethral sexual exposures in the prior 7 days (insertive oral sex [IOS] only, condomless insertive anal intercourse [CIAI] only, IOS with CIAI [IOS + CIAI], or none) and Shannon index, number of species (observed, oral indicator, and rectal indicator), and specific taxa, adjusting for recent antibiotics, age, race/ethnicity, HIV, and pre-exposure prophylaxis. RESULTS:Ninety-six of 108 MSM with NGU attended ≥1 follow-up visit. They contributed 1,140 person-weeks of behavioral data and 1,006 urine specimens. Compared to those with no urethral sexual exposures, those with IOS only had higher Shannon index (P = 0.03) but similar number of species and presence of specific taxa considered, adjusting for confounders; the exception was an association with Haemophilus parainfluenzae. CIAI only was not associated with measured aspects of the urethral microbiota. IOS + CIAI was only associated with presence of H. parainfluenzae and Haemophilus. CONCLUSIONS:Among MSM after NGU, IOS and CIAI did not appear to have a substantial influence on measured aspects of the composition of the urethral microbiota.