Environmental dissemination of multidrug-resistant Escherichia coli across one health interfaces in Mymensingh, Bangladesh

Environmental dissemination of antimicrobial-resistant <i>Escherichia coli</i> is a major One Health challenge in Bangladesh. This study assessed the occurrence of third-generation cephalosporin and carbapenem-resistant <i>E. coli</i> across key environmental interfaces in Mymensingh. In May 2022, 28 water samples were collected from hospital wastewater, livestock effluents, aquaculture ponds, and the Khiro River. Samples were processed via the WHO Tricycle protocol, with 26 isolates undergoing whole-genome sequencing. Third-generation cephalosporin-resistant <i>E. coli</i> were detected in 86% of samples, while carbapenem-resistant isolates (18%) were found exclusively in hospital and river samples. Highest ESBL-producing <i>E. coli</i> concentrations occurred in hospital and poultry wastewater (mean 6.9–7.1 log₁₀CFU/ml). Sequencing identified 93 resistance genes, dominated by <i>bla</i>CTX-M-15 (79%), <i>tet(A)</i> (75%), <i>aadA1</i> (54%), <i>qnrS1</i> (50%), and <i>mph(A)</i> (50%). Carbapenem resistance was associated with blaNDM-5 in hospital and river isolates. While most isolates showed niche-specific clustering in our Phylogenetic analysis, highly conserved core-genome profiles (0 SNPs) between hospital and downstream river isolates (ST2363/ST410) provided strong genomic evidence consistent with effluent-mediated dissemination. These findings highlight the role of wastewater and livestock systems in AMR transmission, underscoring the urgent need for integrated One Health surveillance and improved waste management in Bangladesh.