Acanthamoeba Keratitis
Author: Sushil Tamrakar
General overview of Acanthamoeba Keratitis
Acanthamoeba keratitis is a rare but serious infection of the eye that can result in permanent visual damage or even causes blindness. This infection is caused by free-living amoeba Acanthamoeba. Acanthamoeba causes the disease when it infects the cornea. Acanthamoebae are very common in nature and can be found in water and soil [1].
Summary Data
Badenoch et al (1990) experimented with Acanthamoeba and Corynabacteruim in rats to study the effect of pathogens in the cornea. In that study, the authors inoculated Acanthamoeba (Ac 118) and Corynebacterium organisms into rat corneas. No effect was observed for groups of rats dosed with graded doses of Acanthamoeba alone, while in combination with Corynebacterium, there were some responses at higher doses.
| Experiment serial number |
Reference |
Host type |
Agent strain |
Route |
# of doses |
Dose units |
Response |
Best fit model |
Optimized parameter(s) |
LD50/ID50
|
| 264 |
[2] |
rat |
Ac118 |
eyes -cornea |
4 |
no of trophozoites |
infection |
exponential |
k = 1.01E-04 |
6.89E+03
|
| 265 |
[2] |
rat |
Ac119 |
eyes -cornea |
4 |
no of trophozoites |
infection |
exponential |
k = 3.63E-04 |
1.91E+03
|
| *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 264
Dose response data [2]
| Dose |
Infected |
Non-infected |
Total
|
| 10 |
0 |
8 |
8
|
| 100 |
0 |
16 |
16
|
| 1000 |
2 |
16 |
18
|
| 1E+04 |
5 |
3 |
8
|
|
Goodness of fit and model selection
| Model |
Deviance |
Δ |
Degrees
of freedom |
χ20.95,1
p-value |
χ20.95,m-k
p-value
|
| Exponential
|
0.388
|
0.00767
|
3
|
3.84
0.93
|
7.81
0.943
|
| Beta Poisson
|
0.381
|
2
|
5.99
0.827
|
| 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 |
1.01E-04 |
2.24E-05 |
3.58E-05 |
4.82E-05 |
1.90E-04 |
2.16E-04 |
2.59E-04
|
| ID50/LD50/ETC* |
6.89E+03 |
2.68E+03 |
3.21E+03 |
3.65E+03 |
1.44E+04 |
1.94E+04 |
3.10E+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 265
Dose response data [2]
| Dose |
Infected |
Non-infected |
Total
|
| 10 |
0 |
8 |
8
|
| 100 |
0 |
16 |
16
|
| 1000 |
7 |
17 |
24
|
| 1E+04 |
10 |
0 |
10
|
|
Goodness of fit and model selection
| Model |
Deviance |
Δ |
Degrees
of freedom |
χ20.95,1
p-value |
χ20.95,m-k
p-value
|
| Exponential
|
1.78
|
-0.000219
|
3
|
3.84
1
|
7.81
0.62
|
| Beta Poisson
|
1.78
|
2
|
5.99
0.411
|
| 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 |
3.63E-04 |
2.04E-04 |
2.30E-04 |
2.59E-04 |
5.69E-04 |
5.69E-04 |
7.09E-04
|
| ID50/LD50/ETC* |
1.91E+03 |
9.78E+02 |
1.22E+03 |
1.22E+03 |
2.68E+03 |
3.01E+03 |
3.39E+03
|
| *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
Summary
There was no effect of Acanthamoeba without Corynebacterium.
References
- ↑ CDC. (2012). "Parasites- Acanthamoeba." Retrieved 03/30/2012, 2012, from http://www.cdc.gov/parasites/acanthamoeba/.
- ↑ 2.0 2.1 2.2 2.3 Badenoch, P. R., A. M. Johnson, et al. (1990). "Pathogenicity of Acanthamoeba and Corynebacterium in the Rat Cornea." Archives of Ophthalmology 108: 107-112.
