Spatial Variation of Antibiotic-resistant Escherichia coli along Bagmati River, Kathmandu Valley

BACKGROUND: Antimicrobial resistant Escherichia coli has been reported in Bagmati river of Kathmandu Valley; however, studies on its spatial distribution are lacking, despite being essential for effective water management. Therefore, this cross-sectional study was conducted to determine the spatial distribution of antibiotic-resistant E. coli along Bagmati river from March-September 2025. METHODS: This work was conducted at Department of Microbiology Tri-Chandra Multiple Campus. Water samples collected in duplicate from fifteen sites of Bagmati river were processed for most probable number count and isolation of E.coli. BOD and DO were calculated by Winkler's titrimetric method. Antibiotic susceptibility test was done by disk diffusion technique. Chi square test, correlation assessment, cluster and factor analysis were conducted. RESULTS: The coliform count, E. coli isolates, Biochemical oxygen demand and dissolved oxygen levels ranged from 5-26,500 MPN/100 mL, 0-42, 1.2-418.75 mg/L, and 8.05-0.15 mg/L, respectively, from Baghdwar to Chobar. No E. coli isolates were recovered from Site 1. Cluster analysis based on these variables classified river into four distinct segments, with Sites 1 and 15 forming separate clusters. Significant differences were observed in antibiotic resistance pattern of E. coli isolates across the sampling sites. Factor analysis further grouped the river sites into five clusters, indicating spatial variation in antimicrobial resistant E. coli along the river continuum. CONCLUSIONS: Conventional water quality indicators are insufficient to capture spatial complexity of river health. Integrating fecal contamination and antibiotic resistance patterns provides a more comprehensive assessment of pollution hotspots, supporting targeted management strategies under Nepal's Nationally Determined Contribution (NDC) 3.0.