Abstract and Introduction
Abstract
Background Pharyngeal gonorrhoea is common in homosexual men and may be important in maintaining community prevalence of anogenital infections.
Methods From 2003, all participants in the Health in Men cohort of HIV-negative homosexual men in Sydney were offered annual pharyngeal gonorrhoea screening by BD ProbeTec nucleic acid amplification (NAAT) assay with supplementary porA testing. Participants self-reported diagnoses of pharyngeal gonorrhoea made elsewhere between interviews. Detailed sexual behavioural data were collected 6-monthly.
Results Among 1427 participants enrolled, 65 study-visit-diagnosed pharyngeal gonorrhoea infections were identified (incidence 1.51 per 100 person-years, 95% CI 1.19 to 1.93) of which seven infections were identified on baseline testing (prevalence 0.57%, 95% CI 0.23 to 1.17%). Almost 85% of study-visit-diagnosed pharyngeal infections occurred without concurrent anogenital gonorrhoea. The combined incidence of study-visit-diagnosed and self-reported pharyngeal gonorrhoea (n=193) was 4.45 per 100 person-years (95% CI 3.86 to 5.12). On multivariate analysis, incident infection was associated with younger age (p-trend=0.001), higher number of male partners (p-trend=0.002) and reported contact with gonorrhoea (p<0.001). Insertive oro-anal sex ('rimming') was the only sexual behaviour independently associated with incident pharyngeal gonorrhoea (p-trend=0.044).
Conclusions The majority of pharyngeal gonorrhoea occurred without evidence of concurrent anogenital infection, and the high incidence-to-prevalence ratio suggests frequent spontaneous resolution of NAAT-detected infection. The association of pharyngeal gonorrhoea with oro-anal sex indicates that a broader range of sexual practices are likely to be involved in transmission of gonorrhoea to the pharynx than previously acknowledged. Screening the pharynx of sexually active homosexual men could play a role in reducing the prevalence of anogenital Neisseria gonorrhoeae.
Introduction
Neisseria gonorrhoeae infection of the pharynx has been recognised for decades and is commonly identified among men who have sex with men (MSM) in community and clinic-based settings. In contrast to older studies, recent data suggest that the pharynx is the most common site of gonococcal infection in MSM. However, there are no prospective community-based data on the proportion of pharyngeal gonorrhoea which occurs independent of anogenital infection.
The high prevalence of gonorrhoea among MSM is not surprising, given that the gonococcus is more efficiently transmitted via fellatio than cunnilingus, oral sexual behaviours are substantially more common among homosexual than heterosexual men, and behaviour change since the mid-1980s has led to reduced rates of unprotected anal, but not oral, intercourse. We have previously described an association of urethral and anal gonorrhoea with a range of oro-genital and oro-anal sexual behaviours in the Health in Men (HIM) cohort. These and other observational data suggest that the pharynx is a likely source of anogenital gonorrhoea in MSM.
The single published longitudinal study of risk factors for pharyngeal gonorrhoea in MSM assessed only penile–oral contact as a sexual behavioural predictor of infection. However, MSM practice a range of other oral sexual behaviours, none of which have been prospectively investigated as predictors of pharyngeal gonorrhoea. Here, we describe the prevalence, incidence and predictors of pharyngeal N gonorrhoeae among the community-based Health in Men (HIM) cohort of homosexual men in Sydney, Australia.