Mechanistic Modeling of Salmonellosis

Authors: Coleman M.E.¹; Marks H.M.²

Source: Quantitative Microbiology, Volume 2, Number 3, October 2000 , pp. 227-247(21)

Publisher: Springer

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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.

Keywords: dose-response; beta-Poisson; concave and convex curves; salmonellosis; predator-prey

Language: English

Document Type: Regular paper

Affiliations: 1: USDA/ARS/ERRC/MFS, U MD Eastern Shore, 1130 Trigg Hall, Princess Anne, MD 21853 mcoleman@arserrc.gov 2: US Department of Agriculture, Food Safety and Inspection Service, Washington DC, 20250-3700

Publication date: 2000-10-01