title: Interactive effects of temperature, pH, and water activity on the growth kinetics of Shiga toxin-producing Escherichia coli O104:H4 3.
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.
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Juneja
authors.forename: Sudarsan
authors.initials: S
authors.lastname: Mukhopadhyay
authors.forename: Dike
authors.initials: D
authors.lastname: Ukuku
authors.forename: Cheng-An
authors.initials: CA
authors.lastname: Hwang
authors.forename: Vivian C H
authors.initials: VC
authors.lastname: Wu
authors.forename: Harshavardhan
authors.initials: H
authors.lastname: Thippareddi
mesh_terms: D001937:Brassica / Q000737:chemistry / Q000382:microbiology; D004927:Escherichia coli Infections / Q000453:epidemiology; D019453:Escherichia coli O157 / Q000254:growth & development; D005511:Food Handling; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D000455:Medicago sativa / Q000737:chemistry / Q000382:microbiology; D050296:Microbial Viability; D054323:Shiga-Toxigenic Escherichia coli / Q000737:chemistry / Q000145:classification / Q000254:growth & development* / Q000378:metabolism; D013696:Temperature; D014675:Vegetables / Q000737:chemistry / Q000382:microbiology*; D014867:Water / Q000032:analysis / Q000378:metabolism
chemical_list: D014867:Water