Seasonal Analysis of Pathogenic Escherichia coli 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 Escherichia coli 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 E. coli , with 95.52% of samples in summer and 80.87% in winter. While overall E. coli prevalence showed no significant seasonal difference, pathotype prevalence was significantly higher in summer across all sample types, except for the CVD432 gene. E. coli isolated from spring onions had the highest prevalence of E. coli O157:H7 (19.23%) and the stx1 gene (30.76%), while capsicum isolates showed the highest prevalence of stx2 (40.00%), eaeA (20.00%), ipaH (35.00%), and eltB (20.00%) genes. In winter, coriander had the highest E. coli O157:H7 (14.28%), and cucumber isolates had the highest stx1 (19.04%) gene. Isolates from tomato and capsicum recorded elevated stx2 levels (16.00%). Carrot isolates exhibited the highest eaeA prevalence (11.42%), coriander isolates had the highest ipaH occurrence (14.28%), and tomato isolates had the highest eltB levels (16.00%). A significant seasonal difference was observed in only the stx1 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).