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Abstract
Objectives There are few data on the distribution of specific Chlamydia trachomatis serovars among men who have sex with men (MSM) outside clinical settings. To investigate these patterns, serovar determination was performed on chlamydia-positive samples from two community-based cohort studies of HIV-positive and HIV-negative MSM in Sydney, Australia.
Methods From January 2005 to June 2007 all positive C trachomatis pharyngeal, urine and anal samples were evaluated. The serovar of each C trachomatis infection was determined by omp1 gene sequencing with confirmatory quantitative PCR screening. Symptom data were routinely reported by study participants at the time of testing.
Results Serovar determination was possible for 54 samples among 52 participants. Seven samples were not able to be typed. Site-specific symptoms were reported by fewer than 10% of participants diagnosed with pharyngeal and anogenital chlamydia. The most commonly identified serovars were serovar D (n=32, 59.3%, 95% CI 45.0 to 72.4), followed by serovar G (n=11, 20.4%, 95% CI 10.6 to 33.5) and serovar J (n=5, 9.3%, 95% CI 3.1 to 20.3). Only one lymphogranuloma venereum serovar was identified (L2b).
Conclusions This community-based study found a similar distribution of chlamydia serovars to that observed among Australian community-based MSM several years ago, and serovar distribution recently observed among predominantly symptomatic MSM at a Sydney clinic. These findings suggest little change in C trachomatis serovar distribution in Australian MSM over the past decade and a lack of correlation of specific chlamydia serovars with anogenital symptoms among MSM.
- AIN
- Chlamydia trachomatis
- cohort studies
- epidemiology
- HIV
- homosexual
- homosexuality
- Kaposi's sarcoma
- male
- molecular typing
- risk factors
- sexual behaviour
- STD
- STD control
- STD surveillance
Statistics from Altmetric.com
- AIN
- Chlamydia trachomatis
- cohort studies
- epidemiology
- HIV
- homosexual
- homosexuality
- Kaposi's sarcoma
- male
- molecular typing
- risk factors
- sexual behaviour
- STD
- STD control
- STD surveillance
Chlamydia trachomatis is one of the most common sexually transmissible infections (STI) in Australian men who have sex with men (MSM).1 Knowledge of chlamydia serovar distribution in such populations can assist clinicians and public health authorities in monitoring treatment outcomes, outbreak investigations, surveillance of sexual networks and associating specific clinical manifestations.
There are few data on the distribution of specific C trachomatis serovars among MSM outside clinical settings. To investigate these patterns, we performed serovar determination on chlamydia-positive samples from two community-based cohort studies of HIV-positive and HIV-negative MSM in Sydney, Australia.
Methods
The Health in Men (HIM) HIV-negative cohort and the Positive Health (pH) HIV-positive cohort recruited gay community-attached men who were offered annual STI testing from 2003 onwards, as previously described.2 This included C trachomatis and Neisseria gonorrhoeae testing of urine, oropharyngeal swabs and self-collected anal swabs by strand displacement amplification (SDA) (BD ProbeTec; BD Diagnostics, Sparks, Maryland, USA). Symptom data were routinely collected before STI testing at each annual visit and included pharyngeal symptoms (sore throat), penile symptoms (urethral discharge, urethral itch, sores, dysuria) and anal symptoms (discharge, itch, sores, bleeding, tearing, pain on defecation).
From January 2005 to June 2007 all positive C trachomatis pharyngeal, urine and anal samples were evaluated. The serovar of each C trachomatis infection was determined by omp1 gene sequencing with confirmatory quantitative PCR screening as previously described,3 and the proportion of infections caused by each serovar was calculated. Representative omp1 gene sequences were submitted to GenBank under the accession numbers JF437559–JF437566.
Results
At the beginning of the study period there were 952 participants in the HIV-negative HIM cohort and 327 in the HIV-positive pH cohort. The majority of the HIM and pH cohorts were born in Australia or New Zealand (74.2% and 81.9%, respectively) and participants were mostly of Anglo ethnicity (74.2% and 77.6%, respectively). During the study period, 2082 SDA chlamydia tests were performed among participants in the HIM cohort during 2005.1 person-years (PY) of follow-up (90.2% of eligible visits). Two participants had C trachomatis infections at both genital and anal sites. Among HIM participants with chlamydia, none were co-infected with anogenital N gonorrhoeae. In the pH cohort, 521 SDA chlamydia tests were performed over 320.2 PY of follow-up (70.8% of eligible visits). No pH participant was infected with C trachomatis at multiple anatomical sites, nor was any pH participant also infected with anogenital N gonorrhoeae.
Overall in both cohorts, the median age of those infected with C trachomatis was 39 years (range 25–61, IQR 34–48). Two participants were infected with C trachomatis serovar D at both genital and anal sites. Therefore, serovar determination was possible for 54 samples among 52 participants. Seven samples were not able to be typed and were removed from subsequent analysis. Although these seven samples were positive on the multicopy plasmid target of the initial assay used for the detection of C trachomatis, they were negative on the single-copy omp1 gene target due to lower copy numbers in these samples and thus could not be analysed by sequencing.
The distribution of C trachomatis serovars by cohort is shown in table 1. Serovar distribution by site and prevalence of site-specific symptoms in the past week is shown in table 2. The most commonly identified serovars were serovar D (n=32, 59.3%, 95% CI 45.0 to 72.4), followed by serovar G (n=11, 20.4%, 95% CI 10.6 to 33.5) and serovar J (n=5, 9.3%, 95% CI 3.1 to 20.3). As seen in a previous Australian study of MSM in a clinic-based setting,4 genetic variation within C trachomatis serovars was uncommon, with only one variant identified (serovar D; T726C). Symptoms were rare, being reported by under 10% of chlamydia-infected participants overall. Only one case of lymphogranuloma venereum (LGV) was identified (serovar L2b) as previously described.5 The incidence of LGV in the HIV-positive cohort was 0.3 per 100 PY (95% CI 0.008 to 1.7) and the LGV-positive sample was an anal swab from a symptomatic HIV-infected participant in 2005.
Distribution of serovars among 54 C trachomatis-positive samples obtained from community-based HIV-negative and HIV-positive MSM in Sydney
Distribution of serovars by site and associated symptoms among 54 C trachomatis-positive samples obtained from community-based HIV-negative and HIV-positive MSM in Sydney
Conclusion
The most common C trachomatis serovars identified in this community-based sample of Sydney homosexual men were serovars D, G and J. Serovar distribution was similar to that of the only other Australian community-based MSM study from Melbourne sex-on-premises venues in 2001/26 and serovar distributions reported among MSM overseas.7 8
The small number of each serovar detected precluded detailed statistical analyses of chlamydia serovar correlates. Nonetheless, there was little difference in serovar distributions of C trachomatis-infected MSM between our largely asymptomatic community-based sample and MSM diagnosed with chlamydia at Sydney Sexual Health Centre from 2004 to 2008, where urethral and anal symptoms were reported by 68% and 28%, respectively.4 Our findings indicate little change in C trachomatis serovar distribution in Australian MSM over the past decade. Furthermore, similar chlamydia serovar distribution among clinic-based and community-based samples suggests a lack of correlation of specific chlamydia serovars with anogenital symptoms among MSM.
Acknowledgments
The authors would like to thank all the participants, the dedicated pH and HIM study team and the participating doctors and clinics. They also thank Mr Philip Cunningham and Mr Leon McNally from SydPath for performing the original gonorrhoea and chlamydia testing.
Footnotes
Funding The Kirby Institute is funded by the Australian Government Department of Health and Ageing. The views expressed in this publication do not necessarily represent the position of the Australian Government. The Health in Men Cohort study was funded by the National Institutes of Health, a component of the US Department of Health and Human Services (NIH/NIAID/DAIDS: HVDDT award N01-AI-05395), the National Health and Medical Research Council in Australia (NHMRC, project grant no 400944), the Australian Government Department of Health and Ageing (Canberra), and the New South Wales Health Department (Sydney). The Positive Health Cohort study was funded by the Australian Government Department of Health and Ageing (Canberra) and the New South Wales Health Department (Sydney). The views expressed in this publication do not necessarily represent the position of the Australian Government. Testing materials for gonorrhoea and chlamydia were provided by Becton Dickinson Pty Ltd. DJT is supported by a NHMRC training fellowship (no 1013353), FJ is supported by a NHMRC training fellowship (no 571402), AEG is supported by a NHMRC principal research fellowship (no 568819).
Competing interests None.
Ethics approval This study received ethics approval from the Ethics Committee of the University of New South Wales.
Provenance and peer review Not commissioned; externally peer reviewed.