Seasonal Analysis of Pathogenic <i>Escherichia coli</i> Contamination in Vegetables, Washing Water, and Vendor Hygiene: Virulence Group Classification and Antibiotic Resistance

This study, conducted between June 2022 and March 2023 in Dhaka, examined <i>Escherichia coli</i> prevalence in 874 samples from vegetables, vegetable wash water, and hand swabs from vendors during summer and winter. Of the total samples, 782 (89.50%) tested positive for <i>E. coli</i> , with 95.52% of samples in summer and 80.87% in winter. While overall <i>E. coli</i> prevalence showed no significant seasonal difference, pathotype prevalence was significantly higher in summer across all sample types, except for the <i>CVD432</i> gene. <i>E. coli</i> isolated from spring onions had the highest prevalence of <i>E. coli</i> O157:H7 (19.23%) and the <i>stx1</i> gene (30.76%), while capsicum isolates showed the highest prevalence of <i>stx2</i> (40.00%), <i>eaeA</i> (20.00%), <i>ipaH</i> (35.00%), and <i>eltB</i> (20.00%) genes. In winter, coriander had the highest <i>E. coli</i> O157:H7 (14.28%), and cucumber isolates had the highest <i>stx1</i> (19.04%) gene. Isolates from tomato and capsicum recorded elevated <i>stx2</i> levels (16.00%). Carrot isolates exhibited the highest <i>eaeA</i> prevalence (11.42%), coriander isolates had the highest <i>ipaH</i> occurrence (14.28%), and tomato isolates had the highest <i>eltB</i> levels (16.00%). A significant seasonal difference was observed in only the <i>stx1</i> gene, which was higher in summer for all vegetables. Antibiotic susceptibility testing of 1206 isolates revealed widespread resistance, particularly to ampicillin and erythromycin. Significant seasonal differences in resistance were noted in vegetable samples, but not in water and hand swab samples. Multidrug resistance was highest in isolates from spring onions (56.60% in summer) and carrots (71.87% in winter), with extensively drug-resistant isolates highest in mint (2.17% in summer) and carrots (6.25% in winter).