Salmonella serotype newport: Dose Response Models

Salmonella Newport

Author: Sushil Tamrakar

General overview of Salmonella and Salmonellosis

Salmonella enterica serotype Newport is a gram-negative intracellular bacterium of considerable animal and public health concern. It causes significant clinical disease in livestock, particularly cattle, in humans, and in other animal species. Multiple antimicrobial resistant strains of Salmonella Newport have been recorded in the U.S. and Canada (Huston, Wittum et al. 2002).

http://www.cdc.gov/salmonella/typhiTyphimurium-cantaloupe-08-12/

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Summary Data

McCullough and Eisele orally inoculated human volunteers with S. Newport in 1951.

Experiment serial number Reference Host type Agent strain Route # of doses Dose units Response Best fit model Optimized parameter(s) LD50/ID50 235* human Salmonella newport oral 3 CFU infection exponential k = 3.97E-06 1.74E+05 *This model is preferred in most circumstances. However, consider all available models to decide which one is most appropriate for your analysis.

^*Recommended Model

Experiment number 235 is the only available model , hence it is the recommended model

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Optimization Output for experiment 235 (Salmonella Newport

Human/Salmonella newport model data Dose Infected Non-infected Total 152000 3 3 6 385000 6 2 8 1350000 6 0 6

Goodness of fit and model selection Model Deviance Δ Degrees of freedom χ20.95,1 p-value χ20.95,m-k p-value Exponential 0.16 -3.32e-05 2 3.84 1 5.99 0.923 Beta Poisson 0.16 1 3.84 0.689 Exponential is preferred to beta-Poisson; cannot reject good fit for exponential.

Optimized k parameter for the exponential model, from 10000 bootstrap iterations Parameter MLE estimate Percentiles 0.5% 2.5% 5% 95% 97.5% 99.5% k 3.97E-06 1.75E-06 2.16E-06 2.32E-06 7.36E-06 9.04E-06 1.27E-05 ID50/LD50/ETC* 1.74E+05 5.45E+04 7.67E+04 9.41E+04 2.98E+05 3.20E+05 3.97E+05 *Not a parameter of the exponential model; however, it facilitates comparison with other models.

Parameter histogram for exponential model (uncertainty of the parameter)

Exponential model plot, with confidence bounds around optimized model

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References

Huston CL, Wittum TE and Love BC (2002) Persistent fecal Salmonella shedding in five dairy herds. JAVMA 220(5), 650-655.

McCullough NB and Eisele CW (1951) Experimental Human Salmonellosis: III. Pathogenicity of Strains of Salmonella newport, Salmonella derby, and Salmonella bareilly Obtained from Spray-Dried Whole Egg. The Journal of Infectious Diseases 89(3), 209-213.