Novel PCR-based rapid detection strategies for Escherichia coli O157:H7 and Salmonella in meat products
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Accurate and fast detection methods for foodborne pathogens from various food samples have always been important goals for scientists from many research areas. DNA-based PCR techniques cannot differentiate between DNA from live and dead cells. Ethidium bromide monoazide (EMA) is a dye that can bind to DNA of dead cells and prevent its amplification by PCR. An EMA staining step prior to real-time PCR allows for the effective inhibition of DNA contamination from dead cells. With an optimized EMA staining step, the detection range was 10₃ to 10₉ CFU/ml for pure cultures, 10₅ to 10₉ CFU/ml for artificially contaminated poultry samples, and 10₈ to 10₄ CFU/g for ground beef samples. After a 12-h enrichment step, EMA combined real-time PCR could detect as low as 10 CFU/ml Salmonella from poultry products, as well as 10 CFU/g E. coli O157:H7 from ground beef. Quantum dots (QDs) are a family of nanosized particles with a 1 to 10 nm in radius. It has long-term stable photostability, high quantum yield, broad absorption spectra, narrow emission spectra and high signal-to-noise ratio. In this study, bead free QD facilitated detection method was used to detect Salmonella and E. coli O157:H7 cells from pure cultures, it can detect as low as 10 CFU/ml cells. When it was applied to artificially contaminated ground beef, it can detect 10₆ CFU/g cells. After enrichment, it can detect as low as 10 CFU/g Salmonella cells from ground beef.