Multiplex PCR for detection of stx genes of Escherichia coli.

BACKGROUND & OBJECTIVE: Shiga toxin producing Escherichia coli (STEC), which includes both enterohaemorrhagic Esch. coli (EHEC, 0157: 7H) and non-EHEC (non-0157) produces two major Shiga toxins (Stx1 & Stx2). Detection of Stx or stx genes is the only approach to detect all the different types of STEC. A multiplex PCR is used for the detection of stx genes from EHEC and non-EHEC strains isolated from patients of enteritis. METHODS: Ten EHEC and 35 non-EHEC strains obtained from patients with diarrhoea and enteritis were studied. A single and multiplex PCR (mPCR) were used for detection of stx genes using specific primers. In single PCR, the stx 1 and stx 2 genes were amplified separately while in mPCR, the two genes were amplified together in a single reaction. The PCR products were detected by electrophoresis. RESULTS: All the EHEC strains were found to harbour one or both stx genes as detected by single and multiplex PCR. Of the non-EHEC strains tested, 14.28 per cent were positive for stx genes. Multiplex PCR gave similar results and showed 100 per cent agreement with that of single PCR. INTERPRETATION & CONCLUSION: The results indicated that stx genes are common in the EHEC strains but they are less prevalent among non-EHEC strains. Because of simplicity, rapidity and specificity, mPCR assay represents a good alternative to traditional methods for the detection of stx genes of STEC.