TABLE 2.
Model validation results, showing the change in −2 log likelihood associated with modifying and deleting model features
| Model features | Resulta for Acinetobacter baumannii strain: |
|||
|---|---|---|---|---|
| ATCC 19606 | AB307-0294 | FADDI-AB008 | FADDI-AB030 | |
| Simplified model | ||||
| Contribution of susceptible bacteria to viable counts on drug-containing plates, equation 12 | NSa | 77.6 | NS | 96.5 |
| Transition of susceptible bacteria into a dormant, nonculturable, polymyxin-resistant state, equation 3 | 30.6 | 65.9 | 11.6 | 109.8 |
| Constitutively highly polymyxin-resistant bacteria, equation 2 | 488.5 | 391.7 | 338.0 | 281.3 |
| Adaptive resistance, equations 8 and 9 | 82.3 | —b | — | — |
| Alternative model specification | ||||
| Linear relationship between polymyxin concn and bacterial killing | 73.9 | 136.6 | — | 128.9 |
| Three transit compartments for adaptive resistance (instead of one; equation 9) | NS | 38.1 | NS | 51.3 |
| Five transitory compartments for adaptive resistance (instead of one; equation 9) | NS | 74.6 | 24.4 | 50.8 |
a
NS, not significant: the data did not support inclusion of this feature in the model for the respective strain.
b
—, feature lacking: the models that lacked this feature could not be robustly estimated for the respective strain(s), most likely since the simplified model provided very poor curve fits. This strongly suggested that the respective model feature was beneficial and should be included.