Background Low- and middle-income countries (LMIC) continue to rely on syndromic management of syphilis, Chlamydia trachomatis (CT), and Neisseria gonorrhoeae (NG) infections, which may exacerbate HIV epidemics among men who have sex with men (MSM) and transgender women (TW) for whom these infections are frequently asymptomatic. To examine the potential for targeted STI screening to curb HIV transmission among MSM and TW in LMIC, we estimated the prevalence of syphilis and urethral, rectal, and pharyngeal CT and NG infections, as well as HIV co-infection with these STIs among MSM and TW in Tijuana, Mexico.

Methods A sample of HIV-negative (N=125) and newly diagnosed HIV-positive (N=98) MSM and TW recruited via respondent-driven and venue-based sampling for HIV testing in a parent study underwent STI testing in this study (2017–2018). Treponemal rapid tests were used at the point-of-care with positives undergoing confirmatory testing following the reverse syphilis-testing algorithm. Nucleic acid amplification testing of urine and swabs (rectal and pharyngeal) was used to detect CT/NG at three anatomic sites. We used chi-squared tests to compare STI prevalence by HIV status.

Results HIV-positive participants had a higher STI prevalence than HIV-negative participants (55.1% vs 29.0%; p-value <0.0001). Among HIV-positive participants, the prevalence of syphilis was 34.7%, CT infection was 25.5% (9 urine; 17 rectal; 4 pharyngeal), and NG infection was 24.5% (7 urine; 20 rectal; 9 pharyngeal). Among HIV-negative participants, the prevalence of syphilis was 12.0%, CT infection was 13.6% (7 urine; 9 rectal; 2 pharyngeal), and NG infection was 10.5% (3 urine; 8 rectal; 7 pharyngeal). In the absence of extragenital screening, most CT (26/42) and NG (27/37) cases would have been missed.

Conclusion The high prevalence of syphilis, CT, and NG infections among MSM and TW in Tijuana suggests STI screening that includes extragenital tests, particularly at HIV diagnosis, may help curb HIV transmission in this setting.

Disclosure No significant relationships.