Multiplex PCR for detection of stx genes of Escherichia coli

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.

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.

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.

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.