ANTIBIOGRAM, SCREENING OF BIOFILMS, PLASMID PROFILING AND OCCURENCE OF SHIGA TOXIN GENES OF Escherichia coli ISOLATED FROM RAW SALAD VEGETABLES

Abstract

Raw salad vegetables are an essential ingredient of a healthy diet. Minimally processed food or other raw vegetables have become popular since it suits the present necessity as there is no need of further preparations. Although, they pose great health benefits, the consumption of fresh vegetables has also been associated with risk for consumers. Presence of multidrug resistant bacteria in salad vegetables has emerged as a potential health risk to the consumers worldwide. E. coli is one of the most common foodborne pathogen and also considered to be an important reservoir of transferable antibiotic resistance. The present study dealt with the isolation of E. coli from raw salad vegetables and their antibiogram was determined. The present study revealed the prevalence of E. coli isolates was at 47.27% with prevalence of MDR isolates at its highest peak (100%). Plasmid profile showed that all the E. coli isolates harbored plasmid mostly of size of >10kb. Two isolates possessed double plasmids of sizes of approximately 3kb and >10kb while one isolate showed triple plasmid bands of sizes of approximately 2.7kb, 3kb and >10kb. Screening of biofilm formation was done by CRA and TM. MIC and MBC values of pesticides (chlorpyrifos and cypermethrin) by broth microdilution method using 96-well microtiter plate showed that biofilm producing E. coli isolates were more resistant to those pesticides as compared to biofilm non-producers. On performing the PCR assay for the detection of Shiga-Toxin genes, four of E. coli isolates exhibited stx1 gene and none of the isolates exhibited stx2 gene. The raw salad vegetables sold in vegetable markets of Dharan were highly contaminated with E. coli. The prevalence of MDR E. coli implies the emergence of MDR bacteria in salad vegetables at huge extent. The presence of STEC indicates the possible foodborne illnesses to the consumers. Also, biofilm producing E. coli may have greater antimicrobial resistance property compared to biofilm non-producing E. coli.