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 E. coli 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 E. coli in surface waters from the Goranchatbari sub-catchment of Dhaka. Isolates of ESBL E. coli underwent analysis for the major ESBL and pathogenic genes, antibiotic susceptibility, biofilm formation, and genetic diversity. However, the existence of E. coli 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 E. coli (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.