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Page No. : 75-83

ABSTRACT

A study was undertaken to assess the prevalence of shiga toxin producing E. coli (STEC) in water and ready-to-eat (RTE) foods and to evaluate efficacy of PCR for detection of STEC from RTE foods/water after one step enrichment of samples. A total of 570 samples of different sources (100 water, 200 RTE milk products, 230 RTE meat products and 40 RTE vegetable snacks) were screened. The highest occurrence of E. coli was observed in RTE milk products (76%), followed by RTE meat products (35.21%), RTE vegetable snacks (30%) and water (11%). A total of 256 isolates (11 water, 81 RTE meat products, 12 RTE vegetable snacks and 152 RTE milk products) of E. coli screened for the presence of shiga toxin producing gene (stx1 and stx2) by PCR, 3 and 6 isolates from RTE milk products were positive for stx1 and stx2 genes, respectively. The stx1 isolates were from ice cream and milk cake, whereas stx2 positive isolates were from milk cake and rasgolla. However, direct detection of STEC by PCR after one step enrichment of samples in MacConkey broth was not found to be suitable. Only 2 samples (1 each from rasgolla and milk cake) gave positive result for stx2 gene, whereas none of the samples showed positive result for stx1 gene. The characterization of STEC isolates was also done for their ability to cause haemolysis on sheep blood agar and congo red dye binding activity.

Keywords: E. coli, Meat products, milk products, PCR, vegetable snacks, verotoxic, water