Refrigerated storage effect on expression of shiga toxin genes in Escherichia coli O۱۵۷:H۷ in ground meat

Background and Aim : Escherichia coli O۱۵۷:H۷, the main agent of hemorrhagic colitis, produces shiga toxins as key virulence factors. Investigation of pathogenicity of bacteria in broth or broth like modes doesn’t match properly with results obtained from food matrix. So in this work we investigated stx genes expression of E. coli O۱۵۷:H۷ expression in ground beef matrix during ۷ days.Methods : Comparative real-time RT-PCR was used to evaluate stx۱A and stx۲A genes expression of E. coli O۱۵۷:H۷ against glyceraldehyde-۳-phosphate dehydrogenase (GAPDH) as reference gene.Results : Expression of both of the stx genes decreased during storage of ground meat. Expression reduction was progressive during storage but there were no significant differences between different days. So the highest reduction was observed on the last evaluation day (day۷) that was -۳.۳۵ and -۲.۹ for stx۱A and stx۲A, respectively.Conclusion : It seems E. coli O۱۵۷:H۷ possess low risk in prolonged storage in ground beef in terms of stx genes expression. However there are different reports of stx genes expression of E. coli O۱۵۷:H۷ in various food matrixes such as lettuce, milk, fish and fruits. So it could be concluded that several factors are influencing on growth and pathogenicity of bacteria in different mediums and generalizing of results obtained in broth media to food matrix should not be always correct. However in this study it is not obvious that is gene expression reduction is equal to reduction in toxin release?

کلیدواژه ها:

Escherichia coli O۱۵۷:H۷ ، Shiga toxin gene ، Expression ، Ground beef