Detection of Escherichia coli O157 using equal-length double-stranded fluorescence probe in a real-time polymerase chain reaction assay

Fluorescent probe for detection of bacteria: conformational trigger upon bacterial reduction of an azo bridge

Using biomimetic chemical reduction or Clostridium perfringens cell extract containing azoreductase, the dimer-fluorescent probe 2,4-O-bisdansyl-6,7-diazabicyclooct-6-ene, which possesses a conformationally constrained cis-azo bridge, is reduced to the tetra-equatorial 2,4-O-bisdansyl-cyclohexyl-3,5-bisammonium salt which exhibits fluorescence indicative of a dansyl monomer.

Rapid detection of intestinal pathogens in fecal samples by an improved reverse dot blot method

AIM: To develop a new, rapid and accurate reverse dot blot (RDB) method for the detection of intestinal pathogens in fecal samples.

METHODS: The 12 intestinal pathogens tested were Salmonella spp., Brucella spp., Escherichia coli O157:H7, Clostridium botulinum, Bacillus cereus, Clostridium perfringens, Vibrio parahaemolyticus, Shigella spp., Yersinia enterocolitica, Vibrio cholerae, Listeria monocytogenes and Staphylococcus aureus. The two universal primers were designed to amplify two variable regions of bacterial 16S and 23S rDNA genes from all of the 12 bacterial species tested. Five hundred and forty fecal samples from the diarrhea patients were detected using the improved RDB assay.

RESULTS: The methods could identify the 12 intestinal pathogens specifically, and the detection limit was as low as 103 CFUs. The consistent detection rate of the improved RDB assay compared with the traditional culture method was up to 88.75%.

CONCLUSION: The hybridization results indicated that the improved RDB assay developed was a reliable method for the detection of intestinal pathogen in fecal samples.

Detection of viable enterohemorrhagic Escherichia coli O157 using the combination of immunomagnetic separation with the reverse transcription multiplex TaqMan PCR system in food and stool samples

Enterohemorrhagic Escherichia coli O157:H7 is an infectious pathogen and outbreaks have been reported all over the world, specifically in Australia, Canada, Japan, the United States, and in various countries in Europe and South Africa. Therefore, it is necessary to develop rapid methods to determine the target pathogens for food sanitation and disease. Three combinations of primers and probes were designed to detect and identify E. coli O157 using the TaqMan detection system which focuses on the specific genes eae, rfb(O157, and stxII. Reverse transcription (RT) multiplex TaqMan PCR was carried out to accurately detect viable target cells correctly. Furthermore, the acidic pretreatment and immunomagnetic separation (IMS) of food and stool samples also improved the specificity and accuracy of the RT multiplex TaqMan PCR. The developed multiplex TaqMan PCR was effective in differentiating E. coli O157, enterovirulent E. coli, and non-E. coli pathogens from 100 strains which were isolated from clinical patients and the environment. Viable and nonviable cells were also distinguished by this assay. The pretreatment protocol, which included IMS to concentrate and purify the E. coli O157, was developed and the sensitivity of the assay was improved to 10(0) CFU/ml in pure culture, food, and stool samples. The TaqMan PCR assay is a rapid test for the detection of E. coli O157 in food and stool matrices. It shortens the process time and increases the specificity of the pathogens detected. This is critical for improving the safety and sanitation of our food supply.