الفهرس 
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Abstract
Yersinia enterocolitica is a psychrotrophic foodborne pathogen that can cause gastrointestinal disease in humans. Y. enterocolitica is characterized by its capacity to grow at lower degrees and to form biofilm in the food chain. In our study, we aimed to isolate and identify of Yersinia enterocolitica strains from poultry meat sources (chicken, ducks, geese, and pigeons), investigate virulence factors of Yersinia enterocolitica and antimicrobial susceptibility patterns in addition to determining their ability to produce biofilm in Egypt, examine the impacts of storage temperatures on the growth of Y. enterocolitica in poultry meat, analyze of virulence genes expression, ail and yst genes, using SYBR Green real time PCR and test the ability of Y. enterocolitica to survive under conditions of various environmental stresses in vitro. A total of 220 samples were gathered randomly from poultry meat and were subjected to conventional culture techniques in order to isolate Y. enterocolitica strains. The obtained results revealed that the overall prevalence of Y. enterocolitica was 13/220 (5.91%). Y. enterocolitica strains had been recovered from raw chicken meat, raw ducks meat, and raw geese meat at rates of 10/150 (6.67%), 2/40(5%), and 1/23(4.35%), respectively. Pigeon meat samples were negative for Y. enterocolitica. All isolated Y. enterocolitica were confirmed by molecular detection of Y. enterocolitica 16S rRNA gene. PCR technique was applied for detection of two chromosomally located virulence genes of Y. enterocolitica which have a significant importance including ail and yst genes. It has been observed that synergistic presentation of both (ail and yst) genes in 7.69% (1/13) of the tested isolates, while yst amplified in 30.77% (4/13) of the isolates. Y. enterocolitica strains revealed high antimicrobial resistance to several antimicrobials. In this work, biofilm formation was detected by using tube method in 9 (69.23 %) of the tested Y. enterocolitica isolates in vitro, while 4 (30.77 %) isolates did not have the ability to produce biofilm. Significant variations in Y. enterocolitica counts and relative gene expression levels for two virulence genes were found when inoculated poultry meat was stored at (25 °C), ( 4 °C), and (-20 °C). There were variations in counts of Y. enterocolitica when exposed to environmental stresses experiments.