Different molecular approaches used for detection of Escherichia coli O157:H7 from different sources

Escherichia coli (E. coli) O157:H7 was first recognized in 1982 after investigation of two cases of hemorrhagic colitis and hemolytic uremic syndrome. E. coli O157:H7 the shiga toxin producing strain of E. coli are most commonly involved in many outbreaks of human and animal diseases with low infectious dose. Human infections caused by E. coli O157:H7 are due to consumption of undercooked ground beef, raw milk and raw milk products, water, cold sandwiches, vegetables, raw apple cider and person to person contact. Due to low infectious dose and different mode of transmission it is essential to develop more rapid and sensitive methods for detection of shiga toxin producing E. coli. In this review different molecular based detection methods are discussed. PCR speeds up the analysis time and amplify small number of microbes are described along different variations of PCR following DPCR, omitting the tedious step of DNA extraction. Genomic techniques are reviewed along further epidemiological typing like phage typing and biotyping. Biosensors provide real time detection described along with use of fluorescence and microscopy. Emerging technologies including microarray, molecular beacons and lab-on-a-chip are described along with new improvements in molecular beacons. Merits and demerits of each approach discussed are examined throughout the article.