Anatomical site distribution and genotypes of Chlamydia trachomatis infecting asymptomatic men who have sex with men in northeast Thailand

Characteristics of rectal chlamydia among men who have sex with men in southern Taiwan, 2020-2022: An emerging threat of rectal lymphogranuloma venereum L2b

BACKGROUND

The prevalence of rectal chlamydia among men who have sex with men (MSM) without human deficiency virus infection (non-HIV) remains uncertain in Taiwan, and rectal lymphogranuloma venereum (LGV) among MSM has never been reported in the Far East.

MATERIAL AND METHODS

From January 2020 to April 2022, MSM coming for anonymous voluntary counseling and testing, for pre-exposure prophylaxis, and for antiretroviral therapy were enrolled. All participants submitted his fecal samples and completed a QR-code questionnaire. Medical records of those who took regular medical visits for HIV were recorded. Multiplex polymerase chain reaction (PCR) was performed for all fecal samples, and ompA gene sequencing was therefore performed for each Chlamydia-positive fecal sample.

RESULTS

Among 341 MSM during 2020-2022 in southern Taiwan, 21 (6.2%) had rectal chlamydia infection. Risk factors of rectal chlamydia included co-infection with rectal gonorrhea (adjusted odds ratio [AOR] 6.78, 95% confidence interval [CI] 1.44-31.91, P = 0.015) and multiple sexual partners (AOR 1.373, 95% CI 1.002-1.882, P = 0.048). Further ompA gene sequencing from 19 Chlamydia-positive fecal samples revealed that the prevalent genotypes or genovariants were Da (26.3%) and L2b (26.3%), followed by B (21.1%), J (14.3%), and G (9.5%). All cases of rectal LGV genovariant L2b presented as acute proctitis with diarrhea, anal pain, or discharge and were treated successfully with prolonged treatment of doxycycline.

CONCLUSIONS

Rectal gonorrhea and multiple sexual partners are risk factors for rectal chlamydia. Clinicians in Taiwan should be aware of the emerging threat of rectal LGV among MSM with acute proctitis.

Trends in asymptomatic STI among HIV-positive MSM and lessons for systematic screening

The burden of STIs is particularly high in HIV-infected MSM patients. A recent increase in STIs prevalence has been noticed in the US and western European countries. We aim to assess trends in asymptomatic STIs following the publication of recommendations for STIs screening, i.e. Chlamydia (CT) and gonorrhea (NG). Seventeen centers located in the Paris area participated in the study. All asymptomatic HIV-infected MSM patients attending a follow up consultation were proposed to participated in the study. Asymptomatic patients were included over 2 periods: period 1 from April to December 2015 and period 2 from September to December 2017. Etiologic diagnosis of STIs including hepatitis B, C, syphilis, was performed using a serological test, including a non-treponemal titer with a confirmatory treponemal assay for syphilis. CT and NG were screened using a nucleic acid amplification test (NAATs) on 3 anatomical sites, i.e. urine, rectal and pharyngeal. Overall, 781 patients were included: 490 and 291 in periods 1 and 2 respectively. Asymptomatic CT, NG, and syphilis were diagnosed in 7.5%, 4.8% and, 4.2% respectively. The rate of patients having a multisite asymptomatic infection was 10.2% and 21.1% for CT and NG respectively. The most frequently involved anatomical sites for CT and NG asymptomatic infections were anorectal (66.1% and 55.2% respectively) and pharyngeal (47.4% and 60.5% respectively). CT and NG asymptomatic infection increased by 1.3- and 2-fold respectively between the two periods while syphilis decreased by 3 folds. Our results encourage to reconsider multisite screening for CT and NG in asymptomatic HIV positive MSM as the yield of screening urinary samples only might be low. Despite the more systematic STI screening of asymptomatic HIV positive MSM the prevalence of STI is increasing in MSM in France. Therefore, this strategy has not led to alter CT and NG transmission. The decrease of syphilis might involve self-medication by doxycycline, and the intensification of syphilis screening.

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

BACKGROUND

It has been presumed that Chlamydia trachomatis is transmitted between men only through anal or oral sex, but no mathematical models have tested this presumption.

METHODS

To test this presumption, we created 20 compartmental mathematical models of different sexual practices that included both oral and anal sex and calibrated these models to the observed rates of Chlamydia trachomatis infection at three anatomical sites from 4888 men who have sex with men (MSM) in Melbourne Sexual Health Centre during 2018-2019.

RESULTS

A model that included only oral and anal sex could replicate the observed rates of single-site infection at the oropharynx, urethra and rectum alone, but could not replicate infection at more than one of these sites (multisite). However, if we included transmission from sexual practices that followed one another in the same sexual episode (e.g. saliva contamination of the penis from oral sex transmitting chlamydia to the rectum by anal sex), we significantly improved the calibration of multisite infection rates substantially.

CONCLUSIONS

Our modelling study suggests that transmission routes other than just oral and anal sex are necessary to explain the high rate of Chlamydia trachomatis infection at more than one site.