Understanding antibiotic resistance and microbiome changes in STI prevention

STI Prophylaxis and Emergence of Antimicrobial Resistance

Observational University College, London · NCT06778083

This study is trying to see how using doxycycline for STI prevention affects antibiotic resistance and changes in gut bacteria in men who have sex with men.

Quick facts

Study typeObservational
Enrollment108 (estimated)
Ages18 Years and up
SexMale
SponsorUniversity College, London Academic / other
Locations1 site (London)
Trial IDNCT06778083 on ClinicalTrials.gov

What this trial studies

This observational study aims to investigate the risk of antibiotic resistance and alterations in the human microbiome associated with the use of doxycycline for STI prophylaxis among men who have sex with men (MSM). The study will recruit 108 participants, both users and non-users of STI prophylaxis, who will provide throat swabs and stool samples every six months. These samples will be analyzed for bacterial DNA to identify species present and assess antibiotic resistance. Additionally, participants will complete questionnaires to evaluate the acceptability of the prophylaxis approach.

Who should consider this trial

Good fit: Ideal candidates for this study are men aged 18 and older who identify as cis or trans and have sex with men.

Not a fit: Patients currently being treated for an STI or those who have used antibiotics other than doxycycline in the past three months may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could provide insights into the safety and effectiveness of using doxycycline for STI prevention, potentially leading to better public health strategies.

How similar studies have performed: While the approach of assessing antibiotic resistance in relation to STI prophylaxis is relatively novel, similar studies have explored antibiotic use and resistance, indicating potential for valuable findings.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Aged ≥ 18 years.
* Identifies as a man (cis or trans).
* Has sex with men.
* Able to provide informed consent.

Exclusion Criteria:

* Use of an antibiotic other than doxycycline in the 3 months prior to enrolment
* Currently being treated for an STI with doxycycline
* Use of doxycycline within the prior 3 months for an indication other than STI treatment or STI prevention.

Where this trial is running

London

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Sexually Transmitted Infection PreventionAntibiotic ProphylaxisAntibiotic Resistance, BacterialMicrobiomeDoxycyclineDoxyPEPSTI ProphylaxisSTI Prevention
Last reviewed 2026-06-09 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.