Interactive effects of temperature, pH, and water activity on the growth kinetics of Shiga toxin-producing Escherichia coli O104:H4 3

J Food Prot. 2014 May;77(5):706-12. doi: 10.4315/0362-028X.JFP-13-387.

Abstract

The risk of non-O157 Shiga toxin-producing Escherichia coli strains has become a growing public health concern. Several studies characterized the behavior of E. coli O157:H7; however, no reports on the influence of multiple factors on E. coli O104:H4 are available. This study examined the effects and interactions of temperature (7 to 46°C), pH (4.5 to 8.5), and water activity (aw ; 0.95 to 0.99) on the growth kinetics of E. coli O104:H4 and developed predictive models to estimate its growth potential in foods. Growth kinetics studies for each of the 23 variable combinations from a central composite design were performed. Growth data were used to obtain the lag phase duration (LPD), exponential growth rate, generation time, and maximum population density (MPD). These growth parameters as a function of temperature, pH, and aw as controlling factors were analyzed to generate second-order response surface models. The results indicate that the observed MPD was dependent on the pH, aw, and temperature of the growth medium. Increasing temperature resulted in a concomitant decrease in LPD. Regression analysis suggests that temperature, pH, and aw significantly affect the LPD, exponential growth rate, generation time, and MPD of E. coli O104:H4. A comparison between the observed values and those of E. coli O157:H7 predictions obtained by using the U. S. Department of Agriculture Pathogen Modeling Program indicated that E. coli O104:H4 grows faster than E. coli O157:H7. The developed models were validated with alfalfa and broccoli sprouts. These models will provide risk assessors and food safety managers a rapid means of estimating the likelihood that the pathogen, if present, would grow in response to the interaction of the three variables assessed.

MeSH terms

  • Brassica / chemistry
  • Brassica / microbiology
  • Escherichia coli Infections / epidemiology
  • Escherichia coli O157 / growth & development
  • Food Handling
  • Hydrogen-Ion Concentration
  • Kinetics
  • Medicago sativa / chemistry
  • Medicago sativa / microbiology
  • Microbial Viability
  • Shiga-Toxigenic Escherichia coli / chemistry
  • Shiga-Toxigenic Escherichia coli / classification
  • Shiga-Toxigenic Escherichia coli / growth & development*
  • Shiga-Toxigenic Escherichia coli / metabolism
  • Temperature
  • Vegetables / chemistry
  • Vegetables / microbiology*
  • Water / analysis
  • Water / metabolism

Substances

  • Water