Incidence and clearance of Neisseria gonorrhoea and Chlamydia trachomatis at various anatomical sites among men who have sex with men and association with sexual acts: A 12-week prospective cohort study

BACKGROUND: Various sexual acts contribute to Gonorrhoea and Chlamydia infections at various anatomical sites among men who have sex with men (MSM). This study investigates the effects of sexual acts on the incidence and clearance of Gonorrhoea and Chlamydia at the oropharynx, anorectum and urethra among MSM. METHODS: We conducted a 12-week cohort study involving 312 MSM, surveyed their sexual acts and collected Gonorrhoea and Chlamydia test samples weekly. Time-dependent Cox regression was used to examine the associations between sexual acts and incident infection and time to clearance. RESULTS: By week 12, cumulative incidence was 16.4% for Gonorrhoea and 20.0% for Chlamydia, concentrated at the oropharynx and anorectum (urethral infections were rare). For oropharyngeal Gonorrhoea, receptive oral sex (HR = 3.22, 95% CI 1.00-10.35) and insertive rimming (HR = 2.51, 1.16-5.44) increased infection risk. For anorectal Gonorrhoea, receptive rimming increased risk, while higher behavioural consistency was protective (HR = 0.15, 0.03-0.75). For Chlamydia, insertive rimming increased overall infection risk (HR = 2.87, 1.13-7.30). Most site-specific infections cleared within weeks; however, receptive oral sex was associated with slower clearance of oropharyngeal Gonorrhoea (HR = 0.27, 0.10-0.76). CONCLUSION: Receptive oral sex and insertive rimming increase the risk of oropharyngeal Gonorrhoea. Insertive rimming also increases the risk of Chlamydia infection. MSM who engage in oral sex exhibit slower clearance of oropharyngeal Gonorrhoea.