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

Abstract

AbstractEscherichia 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.Practical applicationsMolecular survey using a number of Escherichia coli O157 specific genes through PCR is an easy, rapid, and a reliable method for pathogenic bacteria identification and characterization amidst other indigenous microbial load. Additionally, polymerase chain reaction (PCR)‐based enumeration of E. coli O157 in vegetables assist us in determining the threshold level for forewarning of pathogenic disease outbreaks. Further, the severity of outbreak could be predicted using E. coli O157 specific shiga toxin (stx) and receptor genes (intimin). The presence of E. coli O157 specific shiga toxins and intimins in a pathogen signifies severity and virulence of strains in causing potential outbreaks. PCR‐based studies enables rapid identification of inoculums source (E. coli O157 spread) from farmers field/cattle shed. Thus, it could be reliably used to stop the further spread of disease from the source inoculums during the outbreaks.