Evaluation of different approaches for modeling Escherichia coli O157:H7 survival on field lettuce.
The ability to predict the behavior of Escherichia coli O157:H7 on contaminated field lettuce is essential for the development of accurate quantitative microbial risk assessments. The survival pattern of the species was assessed from several data sets derived from field-based experiments, which were analyzed by regression analysis fitting one monophasic model (log-linear) and two biphasic (Weibull and Cerf's model) models. Probabilistic models were also simulated with @RISK™, integrating the fitted monophasic and biphasic models in order to analyze their impact on the estimate of the extent of die-off subsequent to a contamination event in the field. Regression analysis indicated that E. coli O157:H7 followed a biphasic decay pattern in most cases, with the Weibull and Cerf's model showing similar good fit to individual and pooled survival data. Furthermore, results from the stochastic analysis demonstrated that using the log-linear model could lead to different risk estimates from those obtained with biphasic models, with a lower prevalence in the former scenario as no tailing is assumed in this model. The models and results derived from this work provide the first suitable mathematical base upon which to build probabilistic models to predict the fate of E. coli O157:H7 on field-grown leafy green vegetable.
Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, 4200 Highway 97 South, Summerland, BC, Canada V0H 1Z0.
Robin C
RC
McKellar
Department of Food Science and Technology, University of Córdoba, Córdoba, Spain 14014.
Fernando
F
Peréz-Rodríguez
Department of Food Science and Technology, University of California, One Shields Avenue, Davis, CA, USA 95616-8598.
Linda J
LJ
Harris
Department of Food Science and Technology, University of California, One Shields Avenue, Davis, CA, USA 95616-8598; Western Center for Food Safety, University of California, 1477 Drew Avenue, Davis, CA, USA 95618.
Anne-Laure
AL
Moyne
Canadian Food Inspection Agency, Building 22, 960 Carling Avenue, Ottawa, ON, Canada K1A 0Z2.
Burton
B
Blais
Agriculture and Agri-Food Canada, Southern Crop Protection and Food Research Centre, 1391 Sandford Street, London, ON, Canada N5V 4T3.
Ed
E
Topp
Agriculture and Agri-Food Canada, Atlantic Food and Horticulture Research Centre, 32 Main Street, Kentville, NS, Canada B4N 1J5.
Greg
G
Bezanson
Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, 4200 Highway 97 South, Summerland, BC, Canada V0H 1Z0.
Susan
S
Bach
Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, 4200 Highway 97 South, Summerland, BC, Canada V0H 1Z0. Electronic address: pascal.delaquis@agr.gc.ca.
Pascal
P
Delaquis
D015169:Colony Count, Microbial; D003198:Computer Simulation; D019453:Escherichia coli O157 / Q000502:physiology*; D005516:Food Microbiology / Q000379:methods*; D018545:Lactuca / Q000382:microbiology*; D015233:Models, Statistical
E. coli O157:H7; biphasic model; field lettuce; predictive model; quantitative risk assessment