An estimate of the proportion of symptomatic gonococcal, chlamydial and non-gonococcal non-chlamydial urethritis attributable to oral sex among men who have sex with men: a case–control study

Abstract

Background Sexually transmitted infections of the pharynx are common among men who have sex with men (MSM); the degree to which these infections are transmitted through oral sex is unknown. Methods We conducted a case-control study of MSM attending Public Health – Seattle & King County STD Clinic between 2001 – 2013 to estimate the proportion of symptomatic urethritis cases attributable to oral sex using two methods. First, we categorized men into the following mutually exclusive behavioural categories based on their self-reported sexual history in the previous 60 days: 1) only received oral sex (IOS); 2) 100% condom usage with insertive anal sex plus oral sex (PIAI); 3) inconsistent condom usage with anal sex (UIAI); and 4) no sex. We then determined the proportion of cases in which men reported the oropharynx as their only urethral exposure (IOS and PIAI). Second, we calculated the population attributable risk percent (PAR%) associated with oral sex using Mantel-Haenszel odds ratio estimates. Results Based on our behavioural categorization method, men reported the oropharynx as their only urethral exposure in the past 60 days in 27.5% of gonococcal, 31.4% of chlamydial, and 35.9% non-gonococcal, non-chlamydial (NGNCU) urethritis cases. The PAR%s for symptomatic gonococcal, chlamydial and NGNCU urethritis attributed to oropharyngeal exposure were 33.8%, 2.7% and 27.1% respectively. Conclusions The pharynx is an important source of gonococcal transmission, and may be important in the transmission of chlamydia and other, unidentified pathogens that cause urethritis. Efforts to increase pharyngeal gonorrhoea screening among MSM could diminish STI transmission.

Concordance of chlamydia infections of the rectum and urethra in same-sex male partnerships: a cross-sectional analysis

“…Similarly, there were only two partnerships in which both men had rectal chlamydia in the absence of either man having urethral chlamydia (Additional file 1: Table S1b), which suggests that rectum-to-rectum transmission is also uncommon. These findings also support the notion that pharyngeal-to-urethra and pharynx-to-rectum for chlamydia transmission is likely to be uncommon [15, 16]. …”

Antiseptic mouthwash against pharyngealNeisseria gonorrhoeae: a randomised controlled trial and an in vitro study

“…A cross-sectional study has shown 34% of MSM with urethral gonorrhoea had no insertive anal sex or no unprotected insertive anal sex in the previous 3 months, suggests penile-anal sex may not be the only driver for gonorrhoea 20. Very similar results were reported from a case–control study from Seattle where 34% of urethral gonorrhoea was attributable to oral sex 21. These data are supported by a mathematical model showing gonorrhoea in MSM cannot be eliminated even with 100% of condom use for penile-anal sex 17…”

Investigating factors for increased gonorrhoea re-infection in men who have sex with men attending a genitourinary clinic: a qualitative study

“…This could have led to a degree of bias in those who acquired gonorrhoea from oral sex only and had otherwise adopted safe sex practices as around 33% of gonorrhoea is transmitted from unsafe oral sex. 13 The majority of individuals approached for this study agreed to participate but two, who had more chaotic lifestyles and repeat infections, did not attend clinic or declined to participate.…”