Incidence and duration of incident oropharyngeal gonorrhoea and chlamydia infections among men who have sex with men: Prospective cohort study

Background: This prospective cohort study aimed to determine the natural history and incidence of oropharyngeal gonorrhoea and chlamydia among a cohort of men who have sex with men (MSM) over a 12-week period, and to examine risk factors associated with incident oropharyngeal infections.
Methods: MSM either aged ≥18 years and had a diagnosis of oropharyngeal gonorrhoea by nucleic acid amplification test (NAAT) in the last three months; or aged 18–35 years who were HIV-negative taking PrEP were eligible for this study. Enrolled men were followed for 12 weeks. Oropharyngeal swabs were collected at week 0 (baseline) and week 12 (end of study). Between these timepoints, weekly saliva specimens and the number of tongue-kissing, penile-oral and insertive rimming partners were collected by post. Oropharyngeal
swabs and saliva specimens were tested by NAAT for Neisseria gonorrheae and Chlamydia trachomatis.
Results: The incidence of oropharyngeal gonorrhoea and chlamydia was 56 (95% CI: 30–94) and 4 (95% CI: 1–32) per 100 person-years, respectively. The estimated median duration of oropharyngeal gonorrhoea infection was 28 days (IQR 21–36) and chlamydia was 14 days (IQR 10–17). The incidence rate ratio (IRR) for oropharyngeal gonorrhoea increased with increased number of kissing partners (IRR 1.08; 95% CI: 1.03–1.12; P = 0.001) and increased number of penile-oral sex partners (IRR 1.07; 95% CI: 1.01–1.14; P = 0.016) but not
with increased number of insertive rimming partners (IRR 1.11; 95% CI: 0.95–1.29; P = 0.175) or other demographic factors. The IRR for oropharyngeal chlamydia was not calculated due to small number of cases (n = 2).
Conclusion: Incident oropharyngeal gonorrhoea was associated with tongue-kissing and penile-oral sex partners but not insertive rimming. MSM have a high incidence of oropharyngeal gonorrhoea and the infection is shortlived (i.e. 28 days), suggesting some infections may be missed with three-monthly screening.