Effects of Package Atmosphere and Storage Conditions on Minimizing Risk of Escherichia coli O157:H7 in Packaged Fresh Baby Spinach

Research advances on the contamination of vegetables by Enterohemorrhagic Escherichia coli: pathways, processes and interaction

Enterohemorrhagic Escherichia coli is considered one of the primary bacterial pathogens that cause foodborne diseases because it can survive in meat, vegetables and so on. Understanding of the effect of vegetable characteristics on the adhesion and proliferation process of EHEC is necessary to develop control measures. In this review, the amount and methods of adhesion, the internalization pathway and proliferation process of EHEC have been described during the vegetable contamination. Types, cultivars, tissue characteristics, leaf age, and damage degree can affect EHEC adhesion on vegetables. EHEC cells contaminate the root surface of vegetables through soil and further internalize. It can also contaminate the stem scar tissue of vegetables by rain or irrigation water and internalize the vertical axis, as well as the stomata, necrotic lesions and damaged tissues of vegetable leaves. After EHEC adhered to the vegetables, they may further proliferate and form biofilms. Leaf and fruit tissues were more sensitive to biofilm formation, and shedding rate of biofilms on epidermis tissue was faster. Insights into the mechanisms of vegetable contamination by EHEC, including the role of exopolysaccharides and proteins responsible for movement, adhesion and oxidative stress response could reveal the molecular mechanism by which EHEC contaminates vegetables.

Inhibitory effect of modified atmosphere packaging on Escherichia coli O157:H7 in fresh-cut cucumbers (Cucumis sativus L.) and effectively maintain quality during storage

Modified atmosphere packaging (MAP) can inhibit microbial growth and prolong shelf life of fresh-cut cucumbers. This study compared the effects of different packaging gases on the growth of E. coli O157:H7 and sensory characteristics of fresh-cut cucumbers. Changes in key movement, adhesion, and oxidative stress genes expression of strain under optimal MAP and air were determined. Cell population density, the extracellular carbohydrate complex content and expression of curli fimbriae were evaluated. Results revealed that the growth of E. coli O157:H7 in fresh-cut cucumbers could be effectively inhibited under MAP (atmosphere = 2% O₂, 7% CO₂, 91% N₂), and better maintained the sensory characteristics. Furthermore, the inhibition mechanism was revealed by inhibiting the expression of movement (fliC), adhesion (eaeA) and oxidative stress (rpoS and sodB) genes in E. coli O157:H7, reducing biofilm formation, extracellular carbohydrate production and curli fimbriae expression. Proper MAP can maintain the quality and safety of fresh-cut cucumbers.