Investigation of Frequency and Antimicrobial Resistance Patterns of Shiga Toxigenic Escherichia coli in Vegetable Samples from Tehran, Iran

Contaminated foods with Shiga toxigenic serotypes of Escherichia coli (STEC) can cause diarrhea and severe diseases in consumers. The aim of this study was to investigate frequency of Shiga toxigenic Escherichia coli serotypes and their antibiotic resistance patterns in vegetable samples from Tehran, Iran.

In this study, a total of 97 vegetable samples from 22 urban areas of Tehran, Iran, were investigated, July 2018 to March 2019. To identify Shiga toxigenic Escherichia coli strains, standard method of enrichment and culture in selective media and polymerase chain reaction for verifying presence of stx1 and stx2 genes were used. Presence of eae and ehxA genes was investigated in Shiga toxigenic Escherichia coli isolates. Antibiotic resistance was assessed using disk diffusion method for 15 antibiotics and the multidrug resistance phenotype was assessed.

Shiga toxigenic Escherichia coli strains were isolated in 14/4% of vegetable samples (stx1, stx2, stx1/stx2 of 8, 1 and 5%, respectively). Presence of eae and ehxA genes was shown in 1 and 2% of Shiga toxigenic Escherichia coli isolates, respectively. The highest resistance was detected to trimethoprim-sulfamethoxazole (100%), erythromycin (73.33%) and tetracycline (85.7%) and the lowest against meropenem (0%) and imipenem/ceftazidime (7/7%).

In this study, contamination of vegetables with multidrug resistant Shiga toxigenic Escherichia coli was verified in Tehran, Iran. Further studies on human samples can clarify this contamination.