Prevalence, Antimicrobial Resistance, and Genotypic Characterization of Diarrheagenic Escherichia coli in Foodborne Diarrhea Cases in Wenzhou Based on Whole-Genome Sequencing.

Background: Although Escherichia coli can be an innocuous resident of the gastrointestinal tract, it also has the pathogenic capacity to cause significant diarrheal and extraintestinal diseases. The study aims to investigate the prevalence, antimicrobial resistance, and genotyping of diarrheagenic Escherichia coli (DEC) in foodborne diarrhea cases in Wenzhou City in 2023, providing a scientific foundation for the monitoring and prevention of bacterial foodborne diseases. Method: Fecal samples from patients with diarrhea were collected from four sentinel hospitals for the isolation of DEC. The pathogenic types of DEC were identified using fluorescence quantitative polymerase chain reaction. Antimicrobial susceptibility testing was performed by broth microdilution, while whole-genome sequencing was utilized for genotyping. Clustering analysis based on the EnteroBase database was conducted to assess the genetic similarity of the strains. Results: Among 2591 fecal samples tested, 90 were positive for DEC, resulting in a detection rate of 3.47% (90/2591). The majority of DEC isolates were enterotoxigenic E. coli (ETEC) and enteroaggregative E. coli (EAEC), accounting for 87.78% (79/90) of the total. DEC detection showed a seasonal pattern, with the highest positivity observed in individuals aged 20-39 years. The genotyping of the most prevalent virulence genes in ETEC was estIa/estIb (57.50%, 23/40), while aggR (23.08%) was most common in EAEC. Genotyping revealed high genetic polymorphism among DEC strains, with HC1100_13 being the predominant clone. The prevalence of the resistance gene blaEC was 96.67%. The highest drug resistance rate was observed in ampicillin (68.89%), followed by nalidixic acid (51.11%), and the multidrug resistance rate was 65.56%. Conclusion: ETEC and EAEC were the most common DEC strains detected in Wenzhou in 2023. These strains exhibited significant genetic diversity and displayed considerable antimicrobial and multidrug resistance, highlighting the need for enhanced monitoring and intervention strategies.