High Burden of Sexually Transmitted Infections Among Pre-exposure Prophylaxis (PrEP) Users: Testing and Prevention...

Pre-exposure prophylaxis (PrEP) effectively prevents HIV acquisition but does not protect against other sexually transmitted infections (STIs). Rising STI rates among PrEP users have raised concerns about risk compensation and highlight the need for integrated sexual health strategies. We assessed the prevalence, anatomical distribution, and behavioural determinants of STIs among PrEP users in Spain. This retrospective observational study included 724 individuals receiving daily tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) at a tertiary hospital in Madrid between March and October 2023, with one year of follow-up. Sociodemographic, behavioural, and microbiological data were obtained from medical records and electronic questionnaires. Routine quarterly PCR screening for Neisseria gonorrhoeae, Chlamydia trachomatis, Mycoplasma genitalium, and Trichomonas vaginalis was performed using anal, pharyngeal, and urine samples. During follow-up, 476 participants (65.7%) were diagnosed with at least one STI, accounting for 968 infectious episodes and 1271 pathogen detections. Neisseria gonorrhoeae (35.3%) and Chlamydia trachomatis (30.3%) accounted for two-thirds of episodes, followed by Mycoplasma genitalium (17.4%) and Treponema pallidum (9%). Most positive samples were anal (566; 55.1%), followed by pharyngeal (271; 26.4%) and urinary (190; 18.5%) samples. One participant acquired HIV (0.1%). Younger age, a higher number of sexual partners, and chemsex practices were independently associated with STI diagnosis. The high burden of bacterial STIs, particularly at anal sites, supports systematic multisite testing, adherence support, behavioural interventions, and consideration of additional prevention strategies, including doxycycline post-exposure prophylaxis and future gonococcal vaccines, within PrEP programmes.