Comparative analysis of virulence genes, biofilm production, and antibiotic resistance in Escherichia coli from dogs and humans using rep-PCR.

BACKGROUND: Escherichia coli (E. coli) is a major pathogen responsible for urinary tract and gastrointestinal infections in both humans and dogs and is of serious public health concern due to its potential for severe infections. The aim of this study was to compare the pathogenicity of E. coli strains isolated from dogs and humans using repetitive sequence-based polymerase chain reaction (rep-PCR). METHODS: A total of 30 fecal samples from visiting dogs and 30 samples from veterinarians and other animal-related personnel in Tehran and Qom, Iran was collected. The presence of E. coli was confirmed by phenotypic and biochemical methods (Gram staining, culture on MacConkey and EMB agar, TSI agar, and IMViC tests) followed by identification of virulence genes (bfpB, elt, stx1, hlyA, fimC) by PCR. Susceptibility to antimicrobials was determined using the Kirby-Bauer method and the ability to produce biofilm was assessed. Finally, all isolates were subjected to genomic fingerprinting using rep-PCR. RESULTS: Out of 60 fecal samples, only one E. coli isolate per sample was selected for analysis. All 60 isolates were confirmed and the fimC gene was present in all samples, while the bfpB gene was found in 90% of human samples and 46.4% of animal samples. All isolates had the ability to produce biofilm, with 20% of human samples and 56.6% of animal samples produced strong biofilms. Antimicrobial testing showed high resistance to amikacin (96.6-100%) and fluoroquinolones, but susceptible to nitrofurantoin and gentamicin. Over 90% of isolates were multidrug-resistant, indicating treatment challenges. Based on rep-PCR, the isolates are assigned to 12 different clusters. Of the 12 clusters identified, five contained isolates from both humans and dogs, suggesting potential zoonotic transmission. CONCLUSIONS: The results suggest that E. coli from humans and dogs share the same pathogenic characteristics, with notable differences in biofilm production and antibiotic resistance. The genetic relatedness between some isolates highlights the risk of zoonotic transmission, emphasizing the need for continuous surveillance and a One Health approach to control infections.