Antimicrobial Susceptibility Patterns and Genetic Relatedness Between Diarrheagenic Escherichia coli Pathotypes Isolated from Ready-to-Eat Olivier Salad and Clinical Samples

Diarrheagenic Escherichia coli (DEC) strains are the most prevalent bacteria conveyed by using contaminated water and foods and are related to mild-to-severe diarrhea in humans. The present study aimed to consider the prevalence, antibiotic resistance profile, phototypes, and biofilm formation capacity of E. coli isolates retrieved from Olivier Salad and clinical samples. The current study was performed on ۲۴۶ samples containing Olivier salad and stool samples collected in Tehran from March to August ۲۰۲۲. Microbiological and molecular diagnostic methods were used to detect DEC strains. Disk diffusion and biofilm formation methods were done to evaluate the antimicrobial resistance profile and biofilm formation capacity of the E. coli isolates. Overall, ۱۶.۶% (۴۱/۲۴۶) of E. coli isolates was attained from both Olivier Salad and clinical samples and the prevalence of DEC was ۱۷% (۷/۴۱). The DEC phototypes obtained from the ۴۱ isolates were as follows: enteropathogenic E. coli (EPEC): ۴.۸%, and enterotoxigenic E. coli (ETEC): ۱۲.۱%. Also, no enteroaggregative E. coli (EAEC), enterinvasive E. coli (EIEC), and enteroaggregative E. coli (EHEC) were found. The highest rate of resistance was found for amoxicillin (۱۰۰%), and amongst the DEC strains, all strains exhibited resistance to at least one antibiotic. Isolates obtained from clinical samples had more biofilm formation capacity than food samples. Our finding evidenced the possibility of fecal contamination in foods of animal origin. Also, multi-drug resistances were found between DEC isolated from food that suggested animal-based foods would operate as the reservoir for multi-drug resistance bacteria. Therefore, the assessment of DEC strains obtained from food samples, as well diarrhea samples can improve food safety and prevent foodborne outbreaks.

Keywords:

Escherichia coli , antimicrobial resistance , Ready-to-eat foods , Biofilms , diarrhea