A mathematical risk model for Escherichia coli O157:H7 cross-contamination of lettuce during processing

A stochastic simulation modelling approach was taken to determine the extent of Escherichia coli O157:H7 contamination in fresh-cut bagged lettuce leaving the processing plant. A probabilistic model was constructed in Excel to account for E. coli O157:H7 cross contamination when contaminated lettuce...

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Bibliographic Details
Published in:Food microbiology 2011-06, Vol.28 (4), p.694-701
Main Authors: Pérez Rodríguez, F., Campos, D., Ryser, E.T., Buchholz, A.L., Posada-Izquierdo, G.D., Marks, B.P., Zurera, G., Todd, E.
Format: Article
Language:English
Subjects:
Analysis of variance
Bags
Biological and medical sciences
Chlorination
Computer Simulation
Contamination
Cross-contamination
Escherichia coli
Escherichia coli Infections - prevention & control
Escherichia coli O157 - growth & development
Escherichia coli O157:H7
Food industries
Food microbiology
Food Microbiology - methods
Food-Processing Industry - methods
Fruit and vegetable industries
Fundamental and applied biological sciences. Psychology
Irradiation
Lactuca - microbiology
Lettuce
Lettuces
Mathematical modelling
Mathematical models
Models, Biological
Models, Statistical
Pathogens
Risk
Risk assessment
Sampling plan
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Summary:A stochastic simulation modelling approach was taken to determine the extent of Escherichia coli O157:H7 contamination in fresh-cut bagged lettuce leaving the processing plant. A probabilistic model was constructed in Excel to account for E. coli O157:H7 cross contamination when contaminated lettuce enters the processing line. Simulation of the model was performed using @Risk Palisade© Software, providing an estimate of concentration and prevalence in the final bags of product. Three different scenarios, named S1, S2, and S3, were considered to represent the initial concentration on the contaminated batch entering the processing line which corresponded to 0.01, 1 and 100 cfu/g, respectively. The model was satisfactorily validated based on Standard Error of Prediction (SEP), which ranged from 0.00-35%. ANOVA analysis performed on simulated data revealed that the initial concentration in the contaminated batch (i.e., S1, S2, and S3) did not influence significantly ( p = 0.4) the E. coli O157:H7 levels in bags derived from cross contamination. In addition, significantly different ( p < 0.001) prevalence was observed at the different levels simulated (S1; S2 and S3). At the lowest contamination level (0.01 cfu/g), bags were cross-contaminated sporadically, resulting in very low E. coli O157:H7 populations (mean: ≤2 cfu/bag) and prevalence levels (
ISSN:0740-0020
1095-9998
DOI:10.1016/j.fm.2010.06.008