Effects of chemical and low-temperature treatments and adaption on the responses of virulence factor genes and outer membrane proteins in Escherichia coli O157:H7

Background In the years after the discovery of this pathogen, Escherichia coli O157:H7 has become increasingly prominent, and outbreaks have been reported in many areas. Methods In the current study, we determined the expressions of virulent factor genes shiga-like toxin II ( stxII ) and E. coli attaching and effacing ( eaeA ), in strains that were isolated from cattle feces and a clinical case in Taiwan. In addition, the effects of chemical and low-temperature stresses and adaptions on the expressions of virulent factor genes were investigated. Furthermore, the outer membrane proteins of acid-adapted E. coli O157:H7 TWC01 (TWC01) was separated using two-dimensional electrophoresis, and proteins were identified using mass spectrometry in order to illustrate the changes in protein expression after adaption. Results Expressions of stxII and eaeA in the TWC01 isolated from a clinical case were higher than those in two strains isolated from cattle feces, and both organic and inorganic acid stresses and adaptions enhance the expression of genes encoding virulent factors in strains. In addition, the outer membrane proteins of TWC01 were regulated under hydrochloric acid adaption, indicating induction of acid tolerance and enhancement adhesion in TWC01. Lactic acid treatment of TWC01 resulted in downregulation of channel protein and adherence-related protein expressions. Conclusion The results of this study are helpful in understanding the resistance of locally isolated TWC01 to chemical and low-temperature stresses, and improving the control of this pathogen.