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| − | Smith et al.(2008) studied dose-response model for ''Listeria monocytogenes''- induced stillbirths in nonhuman primates <ref name=Smith></ref> and Williams et al ( 2007 and 2009) explored fetal mortality in guinea pigs after oral exposure <ref name=Williams2007></ref>. | + | Smith et al.(2008)<ref name=Smith></ref> studied dose-response model for ''Listeria monocytogenes''- induced stillbirths in nonhuman primates and Williams et al ( 2007 and 2009)<ref name=Williams2007></ref> explored fetal mortality in guinea pigs after oral exposure. |
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| | {{DRSummaryTableStart|agent=''Listeria monocytogenes''}} | | {{DRSummaryTableStart|agent=''Listeria monocytogenes''}} |
Revision as of 03:48, 12 October 2012
Listeria monocytogenes (Stillbirths in animals)
Author: Sushil Tamrakar
General overview of Listeria monocytogenes
Listeria monocytogenes is a gram-positive rod-shaped 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 [1] .
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 [1].
Summary Data
Smith et al.(2008)[2] studied dose-response model for Listeria monocytogenes- induced stillbirths in nonhuman primates and Williams et al ( 2007 and 2009)[3] explored fetal mortality in guinea pigs after oral exposure.
| Experiment serial number |
Reference |
Host type |
Agent strain |
Route |
# of doses |
Dose units |
Response |
Best fit model |
Optimized parameter(s) |
LD50/ID50
|
| 289,290* |
[2][3] |
pooled |
|
oral |
13 |
CFU |
stillbirths |
beta-Poisson |
α = 4.22E-02 , N50 = 1.78E+09 |
1.78E+09
|
| 289 |
[2] |
rhesus monkeys |
|
oral |
8 |
CFU |
stillbirths |
beta-Poisson |
α = 4E-02 , N50 = 8.26E+08 |
8.26E+08
|
| 290 |
[3] |
guinea pig |
|
oral |
5 |
CFU |
fetal mortality |
beta-Poisson |
α = 9.36E-02 , N50 = 4.67E+07 |
4.67E+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 pooled data (experiment 289 and 290)
Rhesus monkey/Listeria monocytogenes
| Dose |
Stillbirths |
Not stillbirths |
Total
|
| 316 |
0 |
1 |
1
|
| 1580 |
2 |
6 |
8
|
| 1E+04 |
0 |
4 |
4
|
| 2E+04 |
0 |
3 |
3
|
| 1E+05 |
2 |
9 |
11
|
| 126000 |
1 |
4 |
5
|
| 1E+06 |
2 |
7 |
9
|
| 1580000 |
2 |
4 |
6
|
| 1E+07 |
3 |
6 |
9
|
| 1.26E+07 |
2 |
3 |
5
|
| 1E+08 |
3 |
1 |
4
|
| 1.26E+08 |
2 |
2 |
4
|
| 3.98E+10 |
1 |
0 |
1
|
|
Goodness of fit and model selection
| Model |
Deviance |
Δ |
Degrees
of freedom |
χ20.95,1
p-value |
χ20.95,m-k
p-value
|
| Exponential
|
71.8
|
63.9
|
12
|
3.84
1.33e-15
|
21
1.49e-10
|
| Beta Poisson
|
7.88
|
11
|
19.7
0.724
|
| Beta-Poisson fits better than exponential; cannot reject good fit for beta-Poisson.
|
|
Optimized parameters for the beta-Poisson model, from 500 bootstrap iterations
| Parameter
|
MLE estimate
|
Percentiles
|
| 0.5% |
2.5% |
5% |
95% |
97.5% |
99.5%
|
| α
|
4.22E-02
|
1.14E-02 |
1.54E-02 |
1.78E-02 |
1.26E-01 |
1.51E-01 |
2.71E-01
|
| N50
|
1.78E+09
|
1.74E+06 |
4.42E+06 |
7.04E+06 |
2.28E+15 |
8.63E+16 |
8.36E+20
|
|
Parameter scatter plot for beta Poisson model ellipses signify the 0.9, 0.95 and 0.99 confidence of the parameters. 
beta Poisson model plot, with confidence bounds around optimized model
Optimization Output for experiment 289
Rhesus monkey/Listeria monocytogenes [2]
| Dose |
Stillbirths |
Not stillbirths |
Total
|
| 316 |
0 |
1 |
1
|
| 1580 |
2 |
6 |
8
|
| 2E+04 |
0 |
3 |
3
|
| 126000 |
1 |
4 |
5
|
| 1580000 |
2 |
4 |
6
|
| 1.26E+07 |
2 |
3 |
5
|
| 1.26E+08 |
2 |
2 |
4
|
| 3.98E+10 |
1 |
0 |
1
|
|
Goodness of fit and model selection
| Model |
Deviance |
Δ |
Degrees
of freedom |
χ20.95,1
p-value |
χ20.95,m-k
p-value
|
| Exponential
|
51.4
|
47.7
|
7
|
3.84
4.95e-12
|
14.1
7.71e-09
|
| Beta Poisson
|
3.68
|
6
|
12.6
0.72
|
| Beta-Poisson fits better than exponential; cannot reject good fit for beta-Poisson.
|
|
Optimized parameters for the beta-Poisson model, from 10000 bootstrap iterations
| Parameter
|
MLE estimate
|
Percentiles
|
| 0.5% |
2.5% |
5% |
95% |
97.5% |
99.5%
|
| α
|
4E-02
|
9.86E-04 |
9.94E-04 |
1.02E-02 |
1.22E-01 |
1.96E-01 |
3.05E-01
|
| N50
|
8.26E+08
|
1.94E+03 |
4.54E+04 |
5.30E+05 |
8.90E+18 |
6.18E+22 |
4.86E+65
|
|
Parameter scatter plot for beta Poisson model ellipses signify the 0.9, 0.95 and 0.99 confidence of the parameters. 
beta Poisson model plot, with confidence bounds around optimized model
Optimization Output for experiment 290
Guinea pig/Listeria monocytogenes [3]
| Dose |
Fetal mortality |
Not fetal mortality |
Total
|
| 1E+04 |
0 |
4 |
4
|
| 1E+05 |
2 |
9 |
11
|
| 1E+06 |
2 |
7 |
9
|
| 1E+07 |
3 |
6 |
9
|
| 1E+08 |
3 |
1 |
4
|
|
Goodness of fit and model selection
| Model |
Deviance |
Δ |
Degrees
of freedom |
χ20.95,1
p-value |
χ20.95,m-k
p-value
|
| Exponential
|
19.3
|
17.6
|
4
|
3.84
2.71e-05
|
9.49
0.000677
|
| Beta Poisson
|
1.72
|
3
|
7.81
0.632
|
| Beta-Poisson fits better than exponential; cannot reject good fit for beta-Poisson.
|
|
Optimized parameters for the beta-Poisson model, from 10000 bootstrap iterations
| Parameter
|
MLE estimate
|
Percentiles
|
| 0.5% |
2.5% |
5% |
95% |
97.5% |
99.5%
|
| α
|
9.36E-02
|
1.19E-02 |
2.03E-02 |
2.95E-02 |
1.10E+00 |
1.02E+02 |
8.41E+02
|
| N50
|
4.67E+07
|
9.56E+05 |
2.12E+06 |
3.23E+06 |
8.13E+11 |
4.28E+14 |
2.83E+23
|
|
Parameter scatter plot for beta Poisson model ellipses signify the 0.9, 0.95 and 0.99 confidence of the parameters. 
beta Poisson model plot, with confidence bounds around optimized model
Summary
The risk of fetal mortality in nonhuman primate ( rhesus monkeys) and guinea pigs statistically same and hence the pooled model with larger data points is recommended model.
References
- ↑ 1.0 1.1 Todar K (2012) Todar's Online Textbook of Bacteriology.Todar
- ↑ 2.0 2.1 2.2 2.3 Smith, M. A., K. Takeuchi, et al. (2008). "Dose-Response Model for Listeria monocytogenes-Induced Stillbirths in Nonhuman Primates." Infection and Immunity 76(2): 726-731
- ↑ 3.0 3.1 3.2 3.3 Williams, D., E. A. Irvin, et al. (2007)."Dose-Response of Listeria monocytogenes after Oral Exposure in Pregnant Guinea Pigs." Journal of Food Protection 70(5): 1122-1128
Williams D, Castleman J, et al. (2009) Risk of Fetal Mortality After Exposure to Listeria monocytogenes Based on Dose-Response Data from Pregnant Guinea Pigs and Primates. Risk Analysis 29(11): 1495-1505.
