Characterization and comparative analysis of antimicrobial resistance in <i>Escherichia coli</i> from hospital and municipal wastewater treatment plants

The spread of antimicrobial resistance (AMR) poses global health threats, with wastewater treatment plants (WWTPs) as hotspots for its development. Horizontal gene transfer facilitates acquisition of resistance genes, particularly through integrons in <i>Escherichia coli</i>. Our study investigates <i>E. coli</i> isolates from hospital and municipal WWTPs, focusing on integrons, their temporal correlation and phenotypic and molecular characterization of AMR. Samples from hospital and municipal WWTPs were collected over two seasons, pre-monsoon (March-May) and post-monsoon (December-February). From the hospital (hWWTP) and municipal (mWWTP) influents, 45 and 172 <i>E. coli</i> isolates were obtained, respectively. <i>E. coli</i> from hWWTP exhibited significantly higher resistance rates than mWWTP to most tested antimicrobials except tetracycline. The hWWTP isolates showed a higher prevalence (86.7%) of multidrug resistance (MDR) compared with mWWTP (48.3%). The proportion of MDR isolates from mWWTP nearly doubled in the post-monsoon season. Integron positivity was 17.7% (hWWTP) and 19.7% (mWWTP) with common gene cassettes conferring resistance to trimethoprim and aminoglycosides. Phylogroup analysis showed a predominance of group A in hWWTP and group B1 in mWWTP. The study highlights the role of hospital and municipal wastewater in disseminating AMR, with high rates of MDR <i>E. coli</i> and class 1 integrons detected.