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P316 Could number of partners be a risk for antimicrobial resistance? Higher macrolide consumption amongst a core group of PrEP users
  1. C Van Dijck1,2,
  2. T Vanbaelen1,
  3. J Laumen1,2,
  4. C Kenyon1,3
  1. 1Institute of Tropical Medicine Antwerp, Department of Clinical Sciences, HIV/STI Unit, Antwerp, Belgium
  2. 2University of Antwerp, Faculty of Medicine, Vaccine and Infectious Disease Institute, Laboratory of Medical Microbiology, Wilrijk, Belgium
  3. 3University of Cape Town, Division of Infectious Diseases and HIV Medicine, Cape Town, South Africa


Background A core group of men who have sex with men (MSM) may sustain the high sexually transmitted infection (STI) prevalence among HIV-PrEP users. Regular gonorrhea/chlamydia screening/treatment in this core group might reduce STI prevalence, but also augments antimicrobial use. Macrolides in particular affect the resistome and may enhance the spreading of antimicrobial resistance. Using data from a single-center randomized clinical trial in our clinic we aimed to assess if PrEP-users with multiple sexual partners used more macrolides than others.

Methods Between April 2019 and June 2020, 343 PrEP users participated in a trial that assessed if an antiseptic mouthwash could prevent bacterial STIs (NCT03881007). During 3-monthly study visits participants reported their number of casual partners and underwent gonorrhea/chlamydia screening/treatment at the oropharynx, anorectum and urethra. Macrolide use, expressed as defined daily doses per 1000 individuals per day (DID) was compared between individuals with maximum ten versus more partners per three months.

Results Participants (median age 40.0, IQR 32.0–48.0) contributed for 203.0 person-years. They had a median of 10.0 (IQR 5.6–20.0) partners per three months. Bacterial STI incidence (gonorrhea + chlamydia + syphilis) was 126.6 per 100 person-years. Overall macrolide use was 8.48 DID. Macrolide consumption correlated weakly with number of partners (spearman’s rho 0.18, p<0.001). Half (48.5%) of the participants had more than ten partners per three months and accounted for 60.3% of bacterial STIs. At 10.39 DID their macrolide consumption was 1.62 times (95% CI 1.38 – 1.91) that of participants with less partners (6.42 DID) and three times (2.97, 95% CI 2.69–3.27) that of the 2019 general Belgian population (3.50 DID).

Conclusion PrEP users that undergo 3-monthly gonorrhea/chlamydia screening use a multitude of the macrolides used by the general population. Especially those with over ten 3-montlhy partners may be at risk to carry and spread antimicrobial resistance.

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