Anorectal Chlamydia trachomatis infections in Swiss HIVinfected homosexual men

Abstract number: P688

Dang T., Jaton K., Flepp M., Kovari H., Evison J.M., Fehr J., Schmid P., Boffi El Amari E., Odorico M., Tarr P., Greub G.

Objectives: Since 2003, anorectal lymphogranuloma venereum (LGV) and non-LGV Chlamydia trachomatis infections are re-emerging among homosexual men in developed countries. We prospectively assessed the prevalence and risk factors for these infections in HIV-infected homosexual men in a large cohort, the Swiss HIV Cohort Study (SHCS).

Methods: Male homosexual SHCS participants who reported unprotected receptive anal sex and/or symptoms of proctitis during a visit at one of the SHCS centres from April 2007 to March 2008 were eligible. Those enrolled consented to complete a questionnaire and to have an anal swab screened for C. trachomatis DNA by real-time TaqMan PCR. Positive samples were genotyped by ompA gene amplification and sequencing. Demographic, immunologic and virological data were retrieved from the SHCS database.

Results: 149 men were enrolled. 2 were excluded who did not fulfill inclusion criteria, leaving a total of 147 anal swabs from 147 men. The prevalence of anorectal C. trachomatis infection was 10.9% (95% confidence interval [CI] 6.2%-17.6%). Of the 16 C. trachomatis-positive swabs, one LGV was identified from a man presenting with a 7 day history of rectal discharge, tenesmus, and bloody stools. The remaining serotypes were G (n = 5), J (4), E (2) and D (1). Serotype could not be determined in 3 samples. 5/16 men with versus 54/131 men without anorectal C. trachomatis-infection had detectable HIV viraemia >40 copies/ml. In both anorectal Chlamydia-positive and negative groups, 19% of men reported symptoms of proctitis. Having had more than 20 sex partners within the last 2 years was the only identified risk factor for anorectal C. trachomatis infection (odds ratio 5.6, 95% CI 1.87–17.09). Neither infrequent use of condom with occasional partners, nor other risk factors for sexually transmitted infections (STIs), such as drug use, alcohol misuse, fisting, anal toy use or rimming, were associated with anorectal chlamydial infection.

Conclusion: In this HIV-infected population at high risk for STIs, the prevalence of anorectal chlamydial infection is moderate compared to other STIs and we found no evidence of an ongoing LGV outbreak. Nevertheless, since chlamydial infections are commonly asymptomatic and since the risk of transmission of other STIs is high, screening for anorectal C. trachomatis infection should be added to the other routine screening of homosexual men who report unprotected receptive anal sex.