Molecular Detection and Characterization of Virulence Genes in Escherichia coli Isolated from Drinking Water and Raw Food Sources

Abstract

Poor hygiene results in elevated levels of bacterial contamination in drinking water and raw food. Escherichia coli (E. coli) is one good indicator that shows the level of contamination in community water supply. E. coli harbor pathogenic and antibiotic resistance genes that can result in morbidity. The aim of the study is to assess the pathogenicity and antibiotic resistance prevailing in water and food samples collected from Kohat. Twenty samples were collected and subjected to various tests, including biochemical assays and polymerase chain reaction (PCR) to identify E. coli. Antibiogram assays were performed using Kirby disc diffusion method. PCR was employed to identify virulence genes Shiga toxin 1 and 2 (Stx1 and Stx2). 70% of samples were found to have bacteria in them, and the most common were E. coli and other Enterobacteriaceae. Additional testing of E. coli-positive samples confirmed positive Triple Sugar Iron (TSI) results but negative citrate and urease tests. Antibiotic susceptibility testing revealed that most of the bacteria strains are resistant to penicillin, ampicillin, ceftazidime, and cefixime, while some samples showed susceptibility to amoxicillin plus clavulanic acid, cefoxitin, cefepime, cefoperazone + sulbactam, levofloxacin, ceftriaxone, ciprofloxacin, clarithromycin, azithromycin, and doxycycline as per Clinical and Laboratory Standards Institute (CLSI) standards. Three of the isolates were subjected to PCR for the detection of STX1 and STX2 genes confirming the presence of the Stx2 gene in the two E. coli isolates, while Stx1 was absent. Sequence analysis of Stx2 gene showed >98% identity with GenBank sequences. Finally, our comprehensive study confirmed that E. coli is harmful in raw food and drinking water. Phylogenetic analysis, virulence factor discovery, antibiotic resistance profiling, and more help us identify E. coli contamination. This highlights the need for cleanliness and wastewater management.