Bacterial Load of Chlamydia trachomatis in the Posterior Oropharynx, Tonsillar Fossae, and Saliva among Men Who Have Sex with Men with Untreated Oropharyngeal Chlamydia

Abstract

The aim of this study was to determine whether Chlamydia trachomatis could be detected in saliva and if infection is specific to an anatomical site in the oropharynx. Men who have sex with men (MSM) who were diagnosed with oropharyngeal chlamydia at the Melbourne Sexual Health Centre in 2017-2018 were invited to participate upon returning for treatment. Swabs at the tonsillar fossae and posterior oropharynx and a saliva sample were collected. Throat samples were tested for C. trachomatis by the Aptima Combo 2 assay. The bacterial loads of C. trachomatis in all samples were assessed by quantitative PCR (qPCR) detecting the ompA gene. We calculated the positivity and bacterial load of C. trachomatis for all samples. Forty-two MSM were included. The median age was 28 years (interquartile range [IQR], 24 to 33 years). Thirty-two participants (76.2%; 95% confidence interval [CI], 60.5% to 87.9%) had C. trachomatis detected by qPCR at both the tonsillar fossae and the posterior oropharynx, followed by 9.5% (n = 4; 95% CI, 2.7% to 22.6%) positive at the posterior oropharynx only and 4.8% (n = 2; 95% CI, 0.58% to 16.2%) positive at the tonsillar fossae only. Twenty-nine MSM had C. trachomatis detected in saliva (69.0%; 95% CI, 52.9% to 82.3%). The median C. trachomatis load in saliva was 446 copies/ml (IQR, 204 to 1,390 copies/ml), that in the tonsillar fossae was 893 copies/swab (IQR, 390 to 13,224 copies/ml), and that in the posterior oropharynx was 1,204 copies/swab (IQR, 330 to 16,211). There was no significant difference in C. trachomatis load between the tonsillar fossae and the posterior oropharynx (P = 0.119). Among MSM with oropharyngeal chlamydia, nearly three-quarters had chlamydia DNA detected in saliva, although the viability and implications for transmission are unknown.

Oropharyngeal Chlamydia trachomatis in women; spontaneous clearance and cure after treatment (FemCure)

“…Phillips et al showed among MSM with oropharyngeal chlamydia, that nearly three-quarters had chlamydia DNA detected in saliva, but viability was not assessed. 18 The proportion of positive women with viable oropharyngeal CT was 26.1% (12/46), which is lower than proportions of viable CT that we observed in vaginally (94.0%-96.4%) and in rectally CT-infected women (58.0%-66.5%). 17 Although the proportion with viable oropharyngeal CT is relatively small, it may represent relevant infections for ongoing transmission to a sexual partner via oral sex, 19 but possibly also to the own rectal site, via the gastrointestinal canal.…”

Chlamydia trachomatis transmission between the oropharynx, urethra and anorectum in men who have sex with men: a mathematical model

“…saliva) and therefore remain infectious during sequential sexual acts. Chlamydial DNA is detected in genital secretions, including commonly in the saliva (69%) of men who have oropharyngeal chlamydia [45]. Although there have not been studies to assess the viability of chlamydia in saliva, it is commonly reported to be viable in rectal samples (58%) using mRNA and studies using culture suggest it may be viable in the environment [46,47].…”

Analytical Evaluation of the Abbott RealTime CT/NG Assay for Detection of Chlamydia trachomatis and Neisseria gonorrhoeae in Rectal and Pharyngeal Swabs

“…In a systematic review that assessed bacterial loads for C. trachomatis, Vodstrcil et al 11 found considerable variation of bacterial loads by anatomic site, sex, and quantification technique, which limits comparisons. However, more recently, Phillips et al 12 evaluated bacterial loads of C. trachomatis in MSM and found a median of 1204 copies per swab in the posterior oropharynx. Two studies that evaluated C. trachomatis bacterial loads in rectal infections found similar results, with a median log of 3.4 copies/mL (2512) C. trachomatis among women 13 and mean log of 3.5 copies/ mL (3162) C. trachomatis among MSM and women who reported anal sex.…”