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

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.