Effects of lactic acid stress with lactic acid adaptation on the survival and expression of virulence‐related genes in Escherichia coli O157:H7

Abstract

AbstractThis study was aimed to investigate the effects of lactic acid stress with acid adaptation on the survival and expression of virulence‐related genes in Escherichia coli O157:H7 (strains CICC21530, 89, 95, 112, 109, and J42). E. coli were subjected to acid adaption (pH 5.0) for 1–4 hr and then exposed to acid stress (pH 3.5) for 30–120 min. Results showed that exposure to pH 3.5 decreased the survival of E. coli strains, in which strains 109, 112, and J42 had stronger acid resistance. The expression of virulence‐related genes of most strains decreased after exposure to pH 3.5 compared with nonstressed cells. In addition, acid adaptation increased the acid resistance of most strains, except for CICC21530 and J42. And the virulence expression of most acid‐adapted cells decreased or showed no significant changes compared with nonadapted cells. There were no obvious relationships between the survival and expression of virulence‐related genes in E. coli O157:H7 strains. However, variable acid resistance of acid‐adapted strains was existed, and some acid adaptation increased the strain survival and expression of virulence‐related genes, which may still threaten food safety.Practical ApplicationsThis study evaluated the effects of lactic acid stress with acid adaptation on the survival and expression of virulence‐related genes in Escherichia coli O157:H7. Acid adaptation could enhance the survival and virulence expression of some strains, which will threaten the safety of acidic food during processing and storage. Furthermore, variable acid resistance of acid‐adapted strains should be noticed in surveillance and control of E. coli O157:H7 in environment and food, which is beneficial for its scientific and effective risk assessment and control.