A quantitative characterization of antibiotic resistance and its influencing factors in hospital wastewaters across Lebanon.

Antimicrobial resistance poses global environmental and public health challenges, with hospital wastewater serving as a critical reservoir of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB). This study evaluated the diversity and abundance of ARGs, mobile genetic elements (MGEs), and microbial communities in wastewaters of 13 hospitals across Lebanon. 16 S rRNA gene sequencing showed the microbial compositions of wastewaters to be widely variable. Procrustes analysis revealed that these differences influenced wastewater ARG/MGE profiles. High throughput qPCR showed that genes associated with integrons, transposons, plasmids, and insertion sequences were highly prevalent, with 14 genes detected at ≥ 0.01 copies per 16 S rRNA gene copy. Genes conferring resistance to β-lactams, aminoglycosides, tetracyclines, and sulfonamides were the most abundant. Network analysis identified significant co-occurrence patterns among microbial communities, MGEs, and ARGs, highlighting the potential for horizontal gene transfer (HGT) facilitated by specific transposons and integrons associated with particular microbial hosts. Several physicochemical parameters of the wastewaters also showed strong correlations with ARGs, MGEs, and microbes, suggesting that water quality may influence resistance dissemination. These findings underscore the critical need for monitoring of factors influencing ARG dynamics in hospital systems to limit the spread of antimicrobial resistance from clinical settings into the environment.