Isolation, identification and antibiogram of verotoxin producing Escherichia coli from raw salad vegetables at Jashore, Bangladesh

Abstract

Verotoxin-producing E. coli are getting an emergence for human health and day by day, it is also becoming more alarming in the fact that, they are acquiring multidrug-resistant profiles. This study aimed at isolation and identification of verotoxigenic E. coli followed by the antibiogram of the species from salad vegetables at Jashore district in Bangladesh. A total of 119 raw vegetable salad samples were collected from different areas of the Jashore district. The collected samples were initially enriched in nutrient broth and then used for streak plating on MacConkey and followed by Eosin Methylene Blue (EMB) agar media. Escherichia coli species were isolated and identified following observation of the cultural, microscopic, and biochemical characteristics and further analyzed to determine the presence of verotoxin (VT) producing genes through polymerase chain reaction (PCR) using specific primers (VT1, VT2, and Eae). A panel of antibiotics were tested following the disc diffusion method for determining the antibiotic profile. Total 55 (46.22%) E. coli was isolated phenotypically. 6 (10.9%) isolated E. coli showed positive by amplifying verotoxin-producing gene vt1, but none of the samples were positive vt2 and eaeA gene. Antibiogram for 55 E. coli isolates showed the highest resistance to Erythromycin (83.64%), Streptomycin (78.18%), Ceftriaxone (70.91%). On the other hand, the most heightened susceptibility was observed for Nalidixic acid (76.36%). Moreover, six vt1 positive isolates showed a multidrug-resistant profile. Thus, the presence of toxigenic genes in the isolates suggests the proper maintenance and regular monitoring of raw salad items should be increase to ensure healthy life in this region.   Key words: Vegetable salad, Escherichia coli, verotoxin, antimicrobial resistant, polymerase chain reaction (PCR).