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The following is a summary of “Potential Impact of Doxycycline Post-Exposure Prophylaxis on Tetracycline Resistance in Neisseria gonorrhoeae and Colonization with Tetracycline-Resistant Staphylococcus aureus and Group A Streptococcus,” published in the February 2025 issue of Clinical Infectious Diseases by Soge et al. 

Researchers conducted a retrospective study to analyze the impact of doxycycline post-exposure prophylaxis (doxy PEP) on antimicrobial resistance and the microbiome among men who have sex with men (MSM).  

They analyzed Neisseria gonorrhoeae (NG) surveillance data from King County, WA, using joinpoint regression to assess NG-tetracycline resistance (tetR) trends from 2017 to 2024. Among patients of sexual health clinic (SHC), they examined the link between NG-tetR and doxy PEP use and assessed nasopharyngeal colonization with Staphylococcus aureus and Group A Streptococcus (GAS) in 703 MSM patients of SHC from August 2023 to July 2024.  

The results showed that among 2,312 MSM with NG, tetR remained stable at 27% from 2017 to quarter 1 (Q1) 2023, then increased to 70% in quarter 2 (Q2) 2024 (P <0.0001) after King County released doxy PEP guidelines in Q2 2023. High-level (HL) tetR in NG rose from 2% in Q1 2021 to 65% in Q2 2024 (P <0.0001). Taking more than 3 doses of doxy PEP per month was linked to both tetR and HL tetR (P ≤0.01 for both), but any doxy PEP use was not. Staphylococcus aureus colonization was lower in doxy PEP users than non-users (27% vs 36%, P =0.02), while tetR S. aureus and GAS colonization were higher in users than non-users (18% vs 8%, P <0.0001 and 9% vs 4%, P =0.008, respectively).  

Investigators concluded that TetR in NG significantly increased among King County MSM, with most now having HL TetR, and that doxy PEP was associated with colonization of other bacteria with antibiotic resistance, indicating off-target effects. 

Source: academic.oup.com/cid/advance-article/doi/10.1093/cid/ciaf089/8045759