Distribution of Tetracycline and β-Lactam Resistance Genes in the Oropharyngeal and Anorectal Mucosa of Men Who Have Sex with Men: An Exploratory Study

Abstract

Certain subgroups of men who have sex with men (MSM) may be characterized by increased antimicrobial exposure and sexual network patterns that favor the emergence and dissemination of antimicrobial resistance. This retrospective study investigated the distribution of selected tetracycline- and β-lactam resistance genes in the oropharyngeal and anorectal mucosa of MSM attending a sexually transmitted infection (STI) clinic and explored their association with demographic and behavioral variables. In early 2025, 49 MSM attending the STI Clinic of IRCCS Azienda Ospedaliero Universitaria in Bologna, Italy, were enrolled. Participants completed a questionnaire and underwent pharyngeal and anorectal swabbing. End-point polymerase chain reaction assays were used to detect tetracycline resistance genes (tet(X), tet(O), tet(W), tet(Q)) and β-lactamase genes (blaOXA-2, blaTEM, blaSHV, blaCTX-M). Overall, 20/49 participants (40.8%) reported antibiotic use in the previous 6 months, and 19/49 (38.7%) reported having >6 sexual partners during the same period. At least one tetracycline resistance gene was detected in all participants (49/49; 100%) at both anatomical sites. In contrast, at least one β-lactamase gene was identified in 38/49 (77.6%) oropharyngeal samples and 42/49 (85.7%) anorectal samples. No statistically significant associations were observed between β-lactamase gene carriage and the variables analyzed. However, in the oropharyngeal mucosa, a numerically higher prevalence was observed among individuals reporting >6 sexual partners, although the difference was not statistically significant (p = 0.061). The oropharyngeal and anorectal mucosae of MSM may represent reservoirs of antimicrobial resistance genes. These findings provide descriptive evidence of the widespread distribution of resistance determinants and highlight the need for further studies to clarify their drivers and clinical relevance.

Keywords

antimicrobial resistance MSM tetracycline β-lactams microbiomes

Get full access to this article

View all access options for this article.

References

1. Djusse

, Gaspari

, Morselli

, et al. Antimicrobial resistance determinants in the oropharyngeal microbiome of ‘men having sex with men’ attending a sexually transmitted infection clinic. Int J STD AIDS 2024;35(10):803–807; doi: 10.1177/09564624241255163

2. Van Dijck

, Laumen

JGE

, de Block

, et al. The oropharynx of men using HIV pre-exposure prophylaxis is enriched with antibiotic resistance genes: A cross-sectional observational metagenomic study. J Infect 2023;86(4):329–337; doi: 10.1016/j.jinf.2023.02.006

3. Kenyon

, Baetselier

, Wouters

. Screening for STIs in PrEP cohorts results in high levels of antimicrobial consumption. Int J STD AIDS 2020;31(12):1215–1218; doi: 10.1177/0956462420957519

4. Chu

, Glascock

, Donnell

, et al. Impact of doxycycline post-exposure prophylaxis for sexually transmitted infections on the gut microbiome and antimicrobial resistome. Nat Med 2025;31(1):207–217; doi: 10.1038/s41591-024-03274-2

5. Kenyon

, Osbak

. Certain attributes of the sexual ecosystem of high-risk MSM have resulted in an altered microbiome with an enhanced propensity to generate and transmit antibiotic resistance. Med Hypotheses 2014;83(2):196–202; doi: 10.1016/j.mehy.2014.04.030

6. Milanović

, Aquilanti

, Tavoletti

, et al. Distribution of antibiotic resistance genes in the Saliva of healthy omnivores, ovo-lacto-vegetarians, and vegans. Genes (Basel) 2020;11(9):1088; doi: 10.3390/genes11091088

7. Ho

, Yeoh

, Barua

, et al. Systematic review of human gut resistome studies revealed variable definitions and approaches. Gut Microbes 2020;12(1):1700755; doi: 10.1080/19490976.2019.1700755

8. Anthony

, Burnham

, Dantas

, Kwon

. The gut microbiome as a reservoir for antimicrobial resistance. J Infect Dis 2021;223(12 (Suppl 2)):S209–S213; doi: 10.1093/infdis/jiaa497

9. Malin

, von Wintersdorff

CJH

, Penders

, Savelkoul

PHM

, Wolffs

PFG

. Longitudinal fluctuations of common antimicrobial resistance genes in the gut microbiomes of healthy Dutch individuals. Int J Antimicrob Agents 2023;61(3):106716; doi: 10.1016/j.ijantimicag.2023.106716

10.

10. Surgers

, Chiarabini

, Royer

, et al. Evidence of sexual transmission of extended-spectrum β-lactamase-producing enterobacterales: A cross-sectional and prospective study. Clin Infect Dis 2022;75(9):1556–1564; doi: 10.1093/cid/ciac218

11.

11. Boyd

, El Dani

, Ajrouche

, et al. Gut microbiome diversity and composition in individuals with and without extended-spectrum β-lactamase-producing Enterobacterales carriage: A matched case-control study in infectious diseases department. Clin Microbiol Infect 2024;30(9):1154–1163; doi: 10.1016/j.cmi.2024.03.016

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.02 MB