Development of a real-time PCR for Escherichia coli based on gadE, an acid response regulatory gene

Increasingly, molecular methods have become important in identification and confirmation of bacteria at the species level. Rapid molecular methods provide sensitivity and specificity while reducing cost and resources. The primary goal of this study was to develop a real-time PCR assay for identification of Escherichia coli from an agar plate. GadE (gadE) directly regulates the glutamate-dependent acid response system (GDAR) in E. coli and is responsible for survival of at pH 2. Based on gene sequence data, a real-time PCR assay targeting gadE was developed for this purpose. Seventy bacterial isolates recovered from ground beef enrichments and 714 isolates from caecal contents were identified biochemically and tested with the real-time PCR assay developed in this study. The PCR assay and the biochemical identification had 100% agreement on the tested isolates. The gadE real-time PCR assay was demonstrated in this study to be an inexpensive, reliable method for confirming E. coli colonies within 1.5 h from an agar plate, thereby saving on final identification time.