Rapid and simple method by combining FTA™ card DNA extraction with two set multiplex PCR for simultaneous detection of non-O157 Shiga toxin-producing Escherichia coli strains and virulence genes in food samples

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The aim of this research was to optimize two multiplex polymerase chain reaction (PCR) assays that could simultaneously detect six non-O157 Shiga toxin-producing Escherichia coli (STEC) as well as the three virulence genes. We also investigated the potential of combining the FTA™ card-based DNA extraction with the multiplex PCR assays. Two multiplex PCR assays were optimized using six primer pairs for each non-O157 STEC serogroup and three primer pairs for virulence genes respectively. Each STEC strain specific primer pair only amplified 155, 238, 321, 438, 587 and 750 bp product for O26, O45, O103, O111, O121 and O145 respectively. Three virulence genes were successfully multiplexed: 375 bp for eae, 655 bp for stx1 and 477 bp for stx2. When two multiplex PCR assays were validated with ground beef samples, distinctive bands were also successfully produced. Since the two multiplex PCR examined here can be conducted under the same PCR conditions, the six non-O157 STEC and their virulence genes could be concurrently detected with one run on the thermocycler. In addition, all bands clearly appeared to be amplified by FTA card DNA extraction in the multiplex PCR assay from the ground beef sample, suggesting that an FTA card could be a viable sampling approach for rapid and simple DNA extraction to reduce time and labour and therefore may have practical use for the food industry.

Significance and Impact of the Study: Two multiplex polymerase chain reaction (PCR) assays were optimized for discrimination of six non-O157 Shiga toxin-producing Escherichia coli (STEC) and identification of their major virulence genes within a single reaction, simultaneously. This study also determined the successful ability of the FTA™ card as an alternative to commercial DNA extraction method for conducting multiplex STEC PCR assays. The FTA™ card combined with multiplex PCR holds promise for the food industry by offering a simple and rapid DNA sample method for reducing time, cost and labour for detection of STEC in food and environmental samples.

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