الفهرس 
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Abstract
Abstract
Background and Objective:
Escherichia coli O157:H7 is considered an important zoonotic food-borne pathogen that can cause bloody diarrhea, hemorrhagic colitis (HC), hemolytic-uremic syndrome (HUS), and thrombotic thrombocytopenic purpura (TTP) in humans.
E. coli O157:H7 can enter a viable but nonculturable state as a survival strategy and is considered a threat to public health and food safety. Pathogens in this dormant state can escape detection by conventional methods, so we used propidium monoazide in combination with real-time PCR for the amplification of the DNA of only viable cells to detect viable culturable and VBNC E. coli O157:H7.
In this study, we compared the conventional culture method, conventional PCR method, and propidium monoazide in combination with the SYBR green real-time PCR method for the detection of viable E. coli O157:H7 (viable culturable and viable but nonculturable) to suggest the most rapid, sensitive, suitable, and accurate method.
Material and Methods: This study was carried out on 500 samples (300 samples of frozen meat and 200 samples of raw milk) collected from different supermarkets all over Menoufia, Egypt. The incidence of E. coli O157:H7 was evaluated by using three microbiological methods: culturing, PCR (amplification of the poA gene), and PMA in combination with SYBR green real-time PCR. All meat and milk samples were subjected to the conventional culture method; culture-positive samples were subjected to biochemical and serological identification, while culture-negative samples were subjected to cPCR, then subsequently to PMA SYBR green real-time PCR.
We made a comparison between all used methods for the accuracy, specificity, and sensitivity of these methods.
Result: The incidence of E. coli O157:H7 was 3% as apositive result in a total of samples, and then the culture-negative sample was subjected to PMA-Real-time PCR, the incidence of VBNC E. coli O157:H7 were 0.21%
Conclusion: This study showed that conventional methods and immunoassay methods are not able to detect VBNC E. coli O157:H7 that give a false negative result, and conventional PCR is not able to differentiate between dead and live bacterial cells that give false positive results, but the PMA real-time PCR method has appropriate efficiency and sensitivity for rapid screening of E. coli O157:H7 with no false positive results.
Key Words: VBNC, E. coli O157:H7, Food Poisoning, Propidium monoazide and Real-time PCR.