Mechanistic Modeling of Salmonellosis |
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Authors: | Coleman Margaret E Marks Harry M |
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Institution: | (1) USDA/ARS/ERRC/MFS, U MD Eastern Shore, 1130 Trigg Hall, Princess Anne, MD, 21853;(2) Food Safety and Inspection Service, US Department of Agriculture, Washington, DC, 20250-3700 |
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Abstract: | The serious limitation of the available human data contributes to the need for making simplifying assumptions for dose-response modeling which has led to frequent use of a single function, the beta-Poisson function, as a default dose-response model form. This function is a concave, low-dose linear function. Sub-linear or convex curves may be more appropriate for some host-pathogen interactions due to the series of highly regulated innate and acquired defense systems of the healthy human body that protect against most microbial challenges. A systematic investigation of the steps of non-typhoid salmonellosis in humans leads to biological motivations for sub-linear, or non-concave, dose-response curves in microbial risk assessment. Three phenomena were identified that might contribute to sub-linear, or non-concave, dose-response curves: (1) clumping of bacterial cells in microcolonies in a food matrix; (2) quorum sensing, or density-dependency in expression of virulence genes or other metabolic actions; and (3) need, at least in some circumstances, for multiple lesions for progression to symptomatic illness. This investigation suggests that microbial risk assessors should routinely employ a variety of model forms in addition to the commonly used beta-Poisson model to depict more fully the uncertainty of the true dose-response model. |
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Keywords: | dose-response beta-Poisson concave and convex curves salmonellosis predator-prey |
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