1. Prevalence of Chlamydia trachomatis and Neisseria gonorrhea infection by anatomic site in a cohort study of men who have sex with men (MSM) in Bangkok, Thailand W. Chonwattana 1, J. Tongtoyai 1, C.S. Todd 1,2,3, S. Pattanasin 1, S. Chaikummao 1, P. Wasinrapee 1, A. Varangrat 1, S. Lokpichart 4, T. Holtz 1,5, A. Chitwarakorn 6, M. Curlin 1,5 1 Thailand MOPH-US CDC Collaboration, Nonthaburi, Thailand 2 FHI360 - Asia Pacific Regional Office, Bangkok, Thailand 3 AVRAM Corporation, Miami, United States 4 Thai Bureau of AIDS, TB and STD, Department of Disease Control, MOPH, Bangkok, Thailand 5 Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, United States, 6 Thailand Ministry of Public Health, Nonthaburi, Thailand

2. Background Chlamydia trachomatis (CT) and Neisseria gonorrhea (NG) are among the most prevalent bacterial sexually transmitted infections (STIs) Men who have sex with men (MSM) are at increased risk of acquiring these infections through high-risk sexual practices The CDC recommends routine screening sexually active MSM for urethral and rectal CT/NG, and for pharyngeal NG Prevalence of CT and NG by anatomic site were examined to assess the disease burden and need for prevention Thai, male at birth, ≥ 18, had history of insertive or receptive sex with other man Infections determined by NAAT or culture Symptomatic cases defined during clinical assessment

3. Results Anatomic sites CT infectionNG infectionSame site co-infection n/N% (95% CI)n/N% (95% CI)n/N% (95% CI) Urethral78/17434.5 (3.6-5.6)32/17431.8 (1.3-2.6)4/17430.2 (0.1-0.6) Rectal151/15969.5 (8.1-11.0)97/15966.1 (5.0-7.4)36/15962.3 (1.6-3.1) Pharyngeal63/17373.6 (2.8-4.6)8/17400.5 (0.2-0.9)00 Multiple36/15952.3 (1.6-3.1)7/15950.5 (0.2-0.9)n/a Among 346 infected individuals, only 8.3% (29/346) were symptomatic Among men with rectal symptoms, infection was most often due to CT, 71.4% (5/7) Among men with urethral symptoms, infection was more likely to be due to NG infection, 86.3% (19/22)

4. Discussions Prevalence of pharyngeal NG in this study might be underestimated due to the low sensitivity of culture Evaluation for pharyngeal CT in individuals who engage in sexual practices involving this site, should also be considered Routine screening of asymptomatic persons at high risk of STIs may interrupt further transmission of CT and NG infections as well as prevent the transmission of other STIs including HIV

5. Acknowledgments MSM Volunteer in the cohort Division of HIV/AIDS Prevention, US CDC Bureau of AIDS, TB and STI, Thailand MOPH MSM-Community Advisory Board Silom Community Clinic and support staff HIV/STD Laboratory staff