Antimicrobial Resistance Profile of <i>Escherichia coli</i> Isolated From Hospital and Industrial Wastewater Systems

The global rise of antimicrobial resistance in Escherichia coli poses critical public health challenges, especially in resource-limited settings. This study aimed to investigate the role of untreated hospital sewage and industrially polluted river water as reservoirs for antimicrobial-resistant <i>E. coli</i>. A total of 40 environmental samples were collected, yielding 75 E. coli isolates identified using phenotypic methods. Due to time and resource limitations, 50 isolates were subjected to antimicrobial susceptibility testing by the <i>Kirby-Bauer</i> disk diffusion method against 11 antimicrobial agents. These antimicrobials were selected based on their clinical significance, availability, dominance in resistance mechanism, and utilization trends in Ethiopia. Notably, <i>E. coli</i> isolates from the Yerer River downstream of industrial waste discharge exhibited the highest multi-drug resistance rate (90%), while upstream isolates were fully susceptible to all tested antimicrobials. The Xadacha River isolates showed moderate multi-drug resistance (66.67%). Hospital sewage isolates displayed escalating multi-drug resistance rates across the 3 departments, including the intensive care unit (62.5%), open patient department (91.67%), and inpatient department (100%). Overall, 86.67% of hospital sewage-derived isolates and 65% of river isolates demonstrated multi-drug resistance. Polymerase chain reaction confirmed antimicrobial resistance-associated genes (<i>tetA</i>: 83.33%; <i>blaTEM</i>: 57.14% of the resistant isolates), underscoring hospital sewage and polluted water as critical reservoirs for antimicrobial resistance gene dissemination. The 2 genes were selected based on their availability, phenotypic resistance profile, and nature as sentinel markers for high-use antimicrobial classes in Ethiopia. These findings highlight the urgent need for comprehensive wastewater treatment systems, stricter antimicrobial stewardship, and integrated One Health surveillance to mitigate AMR risks to human, animal, and environmental health.