Molecular characterization of extended-spectrum β-lactamase (ESBL) and virulent genes in multidrug-resistant Escherichia coli isolated from pharmaceutical and environmental Wastewaters in Dhaka, Bangladesh

This study demonstrates that pharmaceutical wastewater in Dhaka, Bangladesh, acts as a significant reservoir for multidrug-resistant (MDR) Escherichia coli. Analysis of isolates from effluent treatment plants (ETPs) and surrounding environmental waters showed high levels of resistance—particularly to β-lactam antibiotics—with ETP isolates exhibiting the highest resistance rates and a high prevalence of the clinically critical blaNDM resistance gene. While last-resort antibiotics such as colistin and meropenem largely remained effective, environmental isolates additionally carried important virulence genes associated with diarrhoeal disease, indicating potential public health risks. Genetic analysis revealed localized clustering of resistant strains, suggesting environmental dissemination linked to pharmaceutical discharge. Overall, the findings highlight pharmaceutical effluents as key drivers of AMR emergence and spread, particularly in low- and middle-income settings.