Acid resistance of Escherichia coli O157:H7 -
a review

Understand how acid tolerance of Escherichia coli O157:H7 can aid its survival both in acid preserved foods and the acidic environment of the stomach and so potentially compromise food safety.

Although most strains of E.coli are harmless inhabitants of the gut of humans and other animals, some are serious pathogens. Acid resistance is believed to be an important factor in the pathogenicity of E.coli - in terms of the bacterium's survival both in foods and in the acid environment of the gut. Understanding the extent and mechanism of this acid resistance is important in preventing problems with pathogenic E.coli O157 and assuring food safety.

This review describes the available scientific evidence for acid resistance in E.coli, by first providing an overview of pathogenic E.coli and the chemistry of acids, and then considering in more detail specific aspects of the mechanism and significance of acid resistance of E.coli as a pathogen. It is aimed at technical personnel, including technical managers and company microbiologists, within food processing, manufacturing and retail companies.

Contents

• Introduction
   - E.coli
   - The chemistry of acids

• Acid resistance
   - Adapted versus non-adapted cells
   - Acidulant variation
   - Strain variation
   - Growth phase
   - Food studies
   - Temperature of storage
   - Cross protection
   - Adaptation mechanisms

• Conclusions and implications for food safety

• Future considerations

• References