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Incidence and duration of incident oropharyngeal gonorrhoea and chlamydia infections among men who have sex with men: prospective cohort study
  1. Eric P F Chow1,2,3,
  2. Lenka A Vodstrcil1,2,
  3. Deborah A Williamson4,
  4. Kate Maddaford1,
  5. Jane S Hocking3,
  6. Melinda Ashcroft4,
  7. Vesna De Petra4,
  8. Catriona S Bradshaw1,2,3,
  9. Christopher K Fairley1,2
  1. 1Melbourne Sexual Health Centre, Alfred Health, Melbourne, Victoria, Australia
  2. 2Central Clinical School, Monash University, Melbourne, Victoria, Australia
  3. 3Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melborune, Victoria, Australia
  4. 4Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
  1. Correspondence to Associate Professor Eric P F Chow, Central Clinical School, Monash University, Carlton, Victoria, Australia; eric.chow{at}


Objectives 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 past 3 months or aged 18–35 years who were HIV-negative taking pre-exposure prophylaxis (PrEP) were eligible for this study. Enrolled men were followed up for 12 weeks. Oropharyngeal swabs were collected at week 0 (baseline) and week 12 (end of study). Between these time points, 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 gonorrhoeae and Chlamydia trachomatis. Poisson regression was performed to examine the risk factors (weekly number of partners) associated with incident oropharyngeal gonorrhoea.

Results A total of 100 MSM were recruited. The incidence of oropharyngeal gonorrhoea and chlamydia was 62 (95% CI 37 to 105) and 9 (95% CI 2 to 35)/100 person-years, respectively. The median duration of incident oropharyngeal infection with gonorrhoea was 28 days (IQR=21–36, n=7). The incidence rate ratio (IRR) for oropharyngeal gonorrhoea increased with an increased number of kissing partners (IRR=1.08; 95% CI 1.03 to 1.12) an increased number of penile-oral sex partners (IRR=1.07, 95% CI 1.01 to 1.14) but not with an increased number of insertive rimming partners (IRR=1.11, 95% CI 0.96 to 1.29) or other demographic factors. The IRR and duration of incident oropharyngeal chlamydia were not calculated due to the small number of cases (n=2).

Conclusions MSM have a high incidence of oropharyngeal gonorrhoea and the median duration of infection was less than 3 months.

  • chlamydia infections
  • epidemiology
  • cohort studies
  • Neisseria gonorrhoeae

Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information.

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Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information.

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  • EPFC and LAV are joint first authors.

  • Handling editor Jonathan Ross

  • Twitter @EricPFChow, @lenkavod, @drdebwilliamson, @JHocking01, @BioMinnie, @Cat_Bradshaw_, @kitfairley

  • Correction notice This article has been corrected since it was first published online. Table 1 has been updated.

  • Contributors EPFC, LAV and CKF conceived and designed the study. EPFC, LAV, KM and CKF designed the study materials. LAV and KM oversaw the ethics approval and study procedures. KM was involved in database management, specimen collection, processing and storage, and performed chart review. LAV performed the statistical analyses. EPFC and JSH assisted with the statistical analyses. EPFC, LAV and CKF wrote the first draft of the manuscript. DW oversaw the laboratory testing results and was assisted by VDP. All authors were involved in revising the manuscript for important intellectual content and approved the final version.

  • Funding This trial was supported by an Australian National Health and Medical Research Council (NHMRC) Project Grant (No. 568971). CKF and CSB are supported by an NHMRC Leadership Investigator Grant (GNT1172900 and GNT1173361, respectively). DW and EPFC are supported by an Australian NHMRC Emerging Leadership Investigator Grant (GNT1174555 and GNT1172873, respectively). JSH is supported by an NHMRC Senior Research Fellowship (GNT1136117).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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