Prevalence of Shiga-like toxin producing Escherichia coli strain (E. coli O157) in freshly consumed vegetables and its characterization

Escherichia coli is a vast genus with various beneficial to harmful species. O157:H7 is a shiga-like toxin (stx) producing E. coli that cause's major health threats in humans, through oral route. However, the presence of E. coli O157: H7 in vegetables is not yet reported in India. Hence, we surveyed the vegetables markets and enumerated the presence of E. coli O157 in freshly consumed vegetables namely, cucumber, radish, lettuce, cabbage, and menthos. Three consecutive surveys from three different market areas were done with 1 month interval. A total of 603 E. coli colonies were isolated. Presence of shiga toxin genes (Stx) were confirmed by colony polymerase chain reaction (PCR) using Stx1 and Stx2 markers that showed 25 and 12 positive colonies, respectively. Among the five vegetables, cabbage had the highest Stx positive colonies (16%). Compared to supermarkets, vegetables from the farmers market did not have much load of E. coli O157. Further, characterization of isolated E. coli colonies were performed using PCR techniques with gene specific markers namely, E. coli uidA, E. coli O157 specific uidA and intimin gene markers. Our analysis showed 6% of E. coli O157 population in the freshly consumed vegetables much above than 2% threshold level, thus providing a warning foresight related to disease outbreak.