Multidrug-resistant ESBL E. coli in urban surface waters and public health implications: A Case Study from Goranchatbari, Dhaka

Surface water pollution from rapid urbanization, industrialization, inadequate sanitation, and excessive agrochemical use is a global crisis. In developing countries, water quality is one of the most urgent environmental issues. The presence of pathogenic extended spectrum β-lactamase (ESBL) producing <i>E. coli</i> in surface water poses a critical public health concern by increasing the risk of waterborne diseases and spreading multidrug-resistant (MDR) infections. This study addresses the severity of surface water pollution in urban Bangladesh, focusing on the molecular characterization of ESBL <i>E. coli</i> in surface waters from the Goranchatbari sub-catchment of Dhaka. Isolates of ESBL <i>E. coli</i> underwent analysis for the major ESBL and pathogenic genes, antibiotic susceptibility, biofilm formation, and genetic diversity. However, the existence of <i>E. coli</i> was confirmed in every sample. Among 266 isolates, 62 (23.31 %) were phenotypically positive for ESBL, with 58 (93.55 %) carrying at least one of the four ESBL genes: CTX-M, TEM, SHV, and OXA. CTX-M was the most prevalent, found in 55 (88.71 %) isolates. Regarding pathogenicity, 25 (40.32 %) isolates were enteric pathogens, including 24 ETEC and a single EIEC. Four non-diarrheagenic isolates were extraintestinal pathogenic <i>E. coli</i> (ExPEC), capable of causing diseases beyond enteric infections. All ESBL isolates were MDR, with high resistance to β-lactam antibiotics, and capable of forming biofilms at 25 °C and 37 °C. ERIC-PCR analysis grouped the isolates into 14 distinct clusters at a 75 % similarity matrix. These water sources critically threaten public health by contaminating nearby freshwater sources with ESBL-producing pathogenic isolates, leading to various hard-to-treat waterborne diseases and risking aquatic biota by deteriorating water quality. Immediate public awareness, proper water treatment, and precise environmental management are needed before using this water for any purpose.