title: Role of colanic acid exopolysaccharide in the survival of enterohaemorrhagic Escherichia coli O157:H7 in simulated gastrointestinal fluids.
abstract: OBJECTIVE
  This study evaluated the production of colanic acid (CA) exopolysaccharide (EPS) by Escherichia coli O157:H7 in relation to the pathogen's ability to survive under acidic conditions simulating the environment in the human gastrointestinal tract.
  
  
  RESULTS
  Escherichia coli O157:H7 W6-13 and its CA-deficient mutant M4020 were examined for their resistance to bile salts, and their ability to survive in simulated gastric fluid containing pepsin (pH 2.0) and simulated intestinal fluid containing pancreatin (pH 8.0). The effect of acid adaptation at pH 5.5 on the survival of E. coli O157:H7 in simulated gastric fluid was also determined. The results indicated that the survivability of M4020, under conditions simulating the environment in the human gastrointestinal tract, reduced more drastically than the viability of W6-13. The presence of bile salts had a slight effect on both types of E. coli O157:H7 cells. The loss of CA did not change the ability of M4020 to respond to acid adaptation.
  
  
  CONCLUSIONS
  The EPS CA may serve as a protective barrier to E. coli O157:H7 for its survival in the human gastrointestinal tract.
  
  
  CONCLUSIONS
  The study contributes to a better understanding of the EPS affecting the ability of E. coli O157:H7 to combat acid stress.
authors.affiliation: Center for Food Safety and Department of Food Science and Technology, The University of Georgia, Griffin, GA 30223-1797, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Mao
authors.forename: M P
authors.initials: MP
authors.lastname: Doyle
authors.forename: J
authors.initials: J
authors.lastname: Chen
mesh_terms: D019453:Escherichia coli O157 / Q000187:drug effects / Q000254:growth & development*; D005750:Gastric Juice / Q000378:metabolism / Q000382:microbiology*; D018869:Heat-Shock Response; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007419:Intestinal Secretions / Q000382:microbiology*; D011134:Polysaccharides / Q000378:metabolism* / Q000494:pharmacology; D011135:Polysaccharides, Bacterial / Q000378:metabolism
chemical_list: D011134:Polysaccharides; D011135:Polysaccharides, Bacterial; C004275:colanic acid