General Overview
Listeria monocytogenes is a Grampositive rodshaped bacterium. It is the causative agent of listeriosis, a serious infection caused by eating food contaminated with the bacteria. The disease generally affects older adults, pregnant women, newborns, and adults with weakened immune systems. However, rarely, persons without these risk factors can also be affected, according to the CDC^{[1]} and Todar^{[2]}.
The overt form of the disease has mortality greater than 25 percent. The two main clinical manifestations are sepsis and meningitis. Meningitis is often complicated by encephalitis, a pathology that is unusual for bacterial infections, according to Todar^{[2]}.
Summary Data
Czuprynski et al.^{[3]} studied susceptibility of C57BL/6 mice and A/J mice to Listeria monocytogenes (strain Scott A) inoculating them intragastrically. Similarly, Golnazarian et al. ^{[4]} also compared infectious dose in normal and compromised C57BL/6J mice with pathogens( strain F5817) via oral route.
Experiment serial number 
Reference 
Host type 
Agent strain 
Route 
# of doses 
Dose units 
Response 
Best fit model 
Optimized parameter(s) 
LD_{50}/ID_{50}

291* 
Golnazarian et al. ^{[4]} 
C57B1/6J mice 
F5817 
oral 
6 
CFU 
death 
exponential 
k = 1.15E05 
6.05E+04 
293 
Czuprynski et al.^{[3]} 
A/J Mice 
Scott A 
intragastric 
3 
CFU 
death 
exponential 
k = 5.71E07 
1.21E+06 
294 
Czuprynski et al.^{[3]} 
C57BL/6 Mice 
Scott A 
intragastric 
3 
CFU 
death 
betaPoisson 
α = 2.71E01 , N_{50} = 7.89E+07 
7.89E+07 
*This model is preferred in most circumstances. However, consider all available models to decide which one is most appropriate for your analysis. 

Optimization Output for experiment 291
C57BL/6J mice/Listeria monocytogenes (Golnazarian et al. ^{[4]})
Dose 
DEATH 
NOT DEATH 
Total 
5500 
1 
9 
10 
32400 
2 
8 
10 
55000 
4 
6 
10 
251000 
10 
0 
10 
550000 
10 
0 
10 
2820000 
10 
0 
10 

Goodness of fit and model selection
Model 
Deviance 
Δ 
Degrees
of freedom 
χ^{2}_{0.95,1} pvalue 
χ^{2}_{0.95,mk} pvalue 
Exponential 
2.22 
0.000453 
5 
3.84 1 
11.1 0.818 
Beta Poisson 
2.22 
4 
9.49 0.695 
Exponential is preferred to betaPoisson; cannot reject good fit for exponential. 

Optimized k parameter for the exponential model, from 500 bootstrap iterations
Parameter 
MLE estimate 
Percentiles 
0.5% 
2.5% 
5% 
95% 
97.5% 
99.5% 
k 
1.15E05 
7.13E06 
7.83E06 
7.96E06 
1.71E05 
1.85E05 
2.07E05 
ID50/LD50/ETC* 
6.05E+04 
3.35E+04 
3.75E+04 
4.06E+04 
8.71E+04 
8.85E+04 
9.73E+04 
*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
Optimization Output for experiment 293
A/J mice/Listeria monocytogenes (Czuprynski et al.^{[3]})
Dose 
DEATH 
NOT DEATH 
Total 
1E+05 
1 
5 
6 
1E+06 
2 
4 
6 
1E+07 
6 
0 
6 

Goodness of fit and model selection
Model 
Deviance 
Δ 
Degrees
of freedom 
χ^{2}_{0.95,1} pvalue 
χ^{2}_{0.95,mk} pvalue 
Exponential 
1.25 
0.0018 
2 
3.84 1 
5.99 0.536 
Beta Poisson 
1.25 
1 
3.84 0.264 
Exponential is preferred to betaPoisson; cannot reject good fit for exponential. 

Optimized k parameter for the exponential model, from 500 bootstrap iterations
Parameter 
MLE estimate 
Percentiles 
0.5% 
2.5% 
5% 
95% 
97.5% 
99.5% 
k 
5.71E07 
2.31E07 
2.31E07 
2.98E07 
1.30E06 
1.49E06 
2.19E06 
ID50/LD50/ETC* 
1.21E+06 
3.17E+05 
4.64E+05 
5.35E+05 
2.32E+06 
3.00E+06 
3.00E+06 
*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
Optimization Output for experiment 294
C57BL/6 mice/Listeria monocytogenes (Czuprynski et al.^{[3]})
Dose 
DEATH 
NOT DEATH 
Total 
1E+07 
1 
5 
6 
1E+08 
4 
2 
6 
1E+09 
4 
2 
6 

Goodness of fit and model selection
Model 
Deviance 
Δ 
Degrees
of freedom 
χ^{2}_{0.95,1} pvalue 
χ^{2}_{0.95,mk} pvalue 
Exponential 
10.7 
9.97 
2 
3.84 0.0016 
5.99 0.00471 
Beta Poisson 
0.752 
1 
3.84 0.386 
BetaPoisson fits better than exponential; cannot reject good fit for betaPoisson. 

Optimized parameters for the betaPoisson model, from 500 bootstrap iterations
Parameter 
MLE estimate 
Percentiles 
0.5% 
2.5% 
5% 
95% 
97.5% 
99.5% 
α 
2.71E01 
9.85E04 
9.98E04 
1.01E03 
1.46E+00 
5.95E+01 
2.41E+05 
N_{50} 
7.89E+07 
9.28E03 
2.42E+02 
2.56E+03 
7.18E+08 
1.90E+09 
1.99E+14 

Parameter scatter plot for beta Poisson model ellipses signify the 0.9, 0.95 and 0.99 confidence of the parameters.
References
 Listeria (Listeriosis), CDC), Centers for Diseas , (2012)
 Todar's Textbook of Bacteriology, Todar, K , (2012)
 A/J Mice Are Susceptible and C57BL/6 Mice Are Resistant to Listeria monocytogenes, Czuprynski, C. J., Faith N. G., and Steinberg H. , Infection and Immunity, Volume 71, p.2, (2003)
 Comparison of infectious dose of Listeria monocytogenes F5817 as determined for normal versus compromised C57B1/6J mice, Golnazarian, C. A., Donnelly C. W., Pintauro S. J., and Howard D. B. , Journal of food protection, Volume 52, p.10, (Submitted)