ABSTRACT
Microbial pathogens may be introduced into surface water sources through agricultural runoff, sewage discharge, or stormwater, and such contamination poses a significant threat to public health. Escherichia coli is a bacterial species that inhabits several environments, including the gastrointestinal tract of humans and warm-blooded animals. E. coli, especially the O157:H7 serotype, is an important indicator species for fecal contamination and possible pathogenicity. The objective of this study was to recover E. coli O157:H7 from the Great Zab River and water treatment projects in Erbil and to investigate its virulence factors and the susceptibility of isolates to silver nanoparticles (AgNPs). A total of 206 water samples, from different sources, were bacteriologically analyzed using Sorbitol MacConkey agar. The presumptive isolates were identified using biochemical tests and the VITEK 2 system. Three E. coli O157:H7 were isolated from the samples. Antimicrobial assays demonstrated the sensitivity of isolates to various AgNP concentrations. One isolate was confirmed by sequencing its 16S rRNA gene. PCR detected the presence of the eae gene in all three isolates, and they are non-Shiga toxin producer, and in one isolate, the fliC gene was detected. All E. coli O157:H7 isolates exhibited a strong ability to form biofilms, indicating their potential for environmental persistence and pathogenicity. Treatment with silver nanoparticles (AgNPs) significantly inhibited biofilm formation, demonstrating their potential as an effective anti-biofilm agent. Furthermore, antimicrobial susceptibility testing revealed that all isolates were sensitive to several major antibiotic classes, including Beta-lactams, Carbapenems, Aminoglycosides, Fluoroquinolones, Tetracyclines, and Polymyxins. These results demonstrate the pathogenic E. coli O157:H7 in the river and the potential application of AgNPs as an antimicrobial in such water bodies.
