Isolation 8t Characterization of Escherichia Coli From Food and Enviro I Mental Samples

Abstract

The ai~ of the present stud~ was to determine the prevalence of Escherichia coli among the food ~n.d environmental samples In and around Meerut (U.P.) region. A total of 210 samples comprtstng 60 from each of sweet and meat, 50 from milk and 40 from environmental samples (20 each of soil and water) were collected aseptically from different shops, dairies and farms in sterile conditions and subjected to primary isolation by inoculating in peptone water broth followed by culture on differential agar media and then on a selective agar media. AIJ the E. coli isolates were found to produce bright pink colour colonies on MacConkey agar and characteristic metallic sheen greenish colour colonies on the Eosin Methylene Blue (EMB) agar. Gram's staining technique was also performed. In Gram's staining technique, all the isolates were pink coloured, small rod shaped, Gram negative bacilli. Biochemical properties of the isolates were studied and reaction in Triple Sugre Iron (TSI) agar slant was also observed to assess diversity among the isolates at phenotypic level. Reactions in TSI agar slant revealed yellow slant and yellow butt with gas but no hydrogen sulphide production. Almost all the E. coli isolates fermented lactose, glucose, sucrose and sorbitol. Among the 210 food and environmental samples, E coli was isolated successfully from only II (5.24%) of them. Further, the isolates were tested for antibiotic sensitivity against 8 antimicrobial agents containing octadiscs. Majority of the isolates were sensitive to Kanamycin and Co-trimazine (72.7%), and to Streptomycin (63.63%) and lowest sensitivity to Amikacin (18.18%). All the isolates were shown resistant to the antibiotics Carbenicilin and majority of isolates show resistance to Tetracycline. All the E. coli isolates were analysed for the presence of Plasmid DNA within the isolates by the alkaline lysis method for plasmid DNA isolation. This study has revealed that none of the I 1 isolates were found to carry plasmid DNA. All E. coli isolates obtained from different food and environmental samples were further characterized by Polymerase Chain Reaction (PCR) to find out prevalence of virulent verotoxic gene VT2 in these isolates to check the hygienic level of samples. These PCR results were checked in 1.5% agarose gel eletrophoresis. PCR results shows that the prevalence of VT2 gene in the isolates was nil (0% ). In conclusion, during this study although the prevalence of Escherichia coli in food and environmental samples is low (5.24% only) but the high lev.el of resistance s~?~n by E.c_ofi i.sol~tes against certain antibiotics such as Carbenicillin and Tetracycline and least sens1ttv1~Y to ant1b1o~t~s h~e Amikacin and Nitrofurantoin shows that these isolates creates problem to the public health res1d1ng tn this area. The results suggest the need for intensive surveillance of colifonns throughout f~od production or processing, always to prevent food-borne infections and also to detect emerg1ng antimicrobial resista isolatesnce