506Mathematical modelling of the transmission of Neisseria gonorrhoeae in men who have sex with men.

Background There is controversy about what sexual practices or secretions (e.g. saliva) transmit Neisseria gonorrhoeae in men who have sex with men (MSM). To date, no studies have modelled potential transmission when one sexual practice follows another in the same sexual encounter or the role of sexual secretions in transmission. Methods We developed eight compartmental models to examine three additional transmission routes: (1) oral sex followed by anal sex (or vice versa); (2) using saliva as a lubricant for penile-anal sex, and (3) oral sex followed by oral-anal sex (rimming) or vice versa. For comparison, we used a baseline model that did not include any of these three transmission routes. The seven other models added one of the additional transmission routes or combinations of the three of them to the baseline model. Results The baseline model could replicate infection at the single anatomical site but underestimated infection at more than one anatomical site ('multi-site infection'). When we added the three transmission routes to the baseline model, oral sex followed by anal sex or vice versa could replicate the prevalence of multi-site infection. The other two transmission routes alone or together could not replicate multi-site infection without the inclusion of oral sex followed by anal sex. Conclusions Our model suggests sexual practices that involve oral followed by anal sex (or vice versa) may be important for explaining the high proportion of multi-site infection. Key messages For Neisseria gonorrhoeae transmission, additional transmission routes are necessary to replicate multi-site infection. [ABSTRACT FROM AUTHOR]