Identification and characterization of Escherichia coli isolated from the surface water of the Laramie River, Wyoming

Surface water is vital for drinking, recreation, wildlife, agriculture, and industry, highlighting the need for routine microbiological monitoring. Escherichia coli (E. coli) in environmental waters serves as a key indicator of fecal contamination and is essential for monitoring water quality. We investigated the phylogenetic diversity, pathogenicity, and antimicrobial resistance (AMR) of E. coli strains isolated from surface water in the Laramie River watershed, used for agriculture and recreation. Phylogenetic analysis of 109 isolates identified phylogroup A as the most prevalent (74.3%), followed by E (11%), B2 (8.2%), and B1 (6.4%), indicating contamination from diverse animal and human sources. Multiplex PCR characterized 7.33% of isolates as diarrheagenic E. coli (DEC), with enterohemorrhagic E. coli (EHEC) and enteropathogenic E. coli (EPEC) the most frequently detected pathotypes (2.75% each). AMR analysis determined that 50.42% of isolates exhibited resistance to at least one antibiotic, with the highest resistance to tetracycline (44.4%) and ampicillin (19.6%). Multiple resistance patterns were associated with wastewater and agricultural runoff, with elevated resistance observed downstream of wastewater treatment plants. These findings provide insights into the interactions between E. coli diversity, pathogenicity, and AMR in the watershed, emphasizing the need for proactive water quality management to address anthropogenic impacts.