Sequential Sex Practices and the Likelihood of Bacterial Sexually Transmitted Infections and Urethritis in Men Who Have Sex With Women.

BACKGROUND

Mathematical modeling studies suggest that sequential sex practices (SSPs) among men who have sex with men are necessary to produce observed rates of bacterial sexually transmitted infections (STIs). Nearly all models of bacterial STIs in opposite-sex partnerships have focused exclusively on urogenital infections, although SSPs may lead to extragenital infections. The frequency of SSPs and their associations with bacterial STIs among men who have sex with women (MSW) is not well-characterized.

METHODS

We utilized data from a 6-month cohort study of male urethritis in Seattle, WA (2014-2018); our analysis included MSW aged ≥16 y. Each month, participants completed questionnaires ascertaining SSPs, were evaluated for nongonococcal urethritis (NGU), and provided urine samples for urethral bacterial STI testing. We identified the most frequent SSPs reported at participants' last sexual encounter before testing and used generalized estimating equations to estimate the probability of positive urethral STI and of NGU.

RESULTS

The 184 participants included in the analysis reported 528 sexual encounters; 76% of sexual encounters included >1 sex act. The most frequently reported SSPs were insertive oral sex followed by vaginal sex (57.4%), vaginal sex only (19.5%), and vaginal sex followed by insertive oral sex (9.5%). Overall, participants had four positive urethral STI tests and 14 cases of NGU without a positive urethral STI test.

CONCLUSIONS

Among MSW, there are clear patterns in the frequency of types of sex and SSPs. These data can inform the development of more robust mathematical models of bacterial STI transmission among MSW.