title: Survival mechanism of Escherichia coli O157:H7 against combined treatment with acetic acid and sodium chloride.
abstract: The combination of salt and acid is commonly used in the production of many foods, including pickles and fermented foods. However, in our previous studies, the addition of salt significantly reduced the inhibitory effect of acetic acid on Escherichia coli O157:H7 in laboratory media and pickled cucumbers. Therefore, this study was conducted to determine the mechanism by which salt confers resistance against acetic acid in E. coli O157:H7. The addition of high concentrations (up to 9% or 15% [w/v]) of salt increased the resistance of E. coli O157:H7 to acetic acid treatment. Combined treatment with acetic acid and salt showed varying results among different bacterial strains (an antagonistic effect for E. coli O157:H7 and Shigella and a synergistic effect for Listeria monocytogenes and Staphylococcus aureus). The addition of salt increased the cytoplasmic pH of E. coli O157:H7, but decreased the cytoplasmic pH of L. monocytogenes and S. aureus on treatment with acetic acid. Therefore, the addition of salt increases the acid resistance of E. coli O157:H7 possibly by increasing its acid resistance response and consequently preventing the acidification of its cytoplasm by organic acids.
authors.affiliation: Department of Food Science and Technology, Chung-Ang University, 72-1 Nae-ri, Daedeok-myeon, Anseong-si, Gyeonggi-do, 456-756, South Korea. Electronic address: nina6026@cau.ac.kr.
authors.forename: Sun-Young
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Department of Food and Animal Biotechnology, Seoul National University, Seoul 151-921, South Korea. Electronic address: kang7820@snu.ac.kr.
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Kang
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology*; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000254:growth & development*; D006863:Hydrogen-Ion Concentration; D050296:Microbial Viability / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D012965:Sodium Chloride; D019342:Acetic Acid
keywords: Acetic acid; Acid resistance response; Cytoplasmic pH; E. coli O157:H7; Salt; Stress interaction