Research Article
Synergistic Effect between Usnic Acid and Polymyxin B against Resistant Clinical Isolates of Pseudomonas aeruginosa
Table 3
Evaluation of usnic acid and polymyxin B interaction by the Checkerboard method.
| Clinical isolates | MIC (μg/mL) | MIC of the combination (μg/mL) | FICI | Interaction | Polymyxin B | Usnic acid | Polymyxin B + usnic acid |
| PA05 | 4 | 500 | 0.25/15.625 | 0.094 | Synergism | PA07 | 4 | 500 | 0.25/15.625 | 0.094 | Synergism | PA18 | 8 | 500 | 0.25/31.25 | 0.094 | Synergism | PA19 | 4 | 500 | 0.5/15.625 | 0.156 | Synergism | PA46 | 32 | 250 | 0.25/7.8125 | 0.039 | Synergism | PA56 | 8 | 250 | 0.25/31.25 | 0.094 | Synergism | PA57 | 32 | 500 | 0.25/15.625 | 0.039 | Synergism | PA78 | 32 | 500 | 0.25/15.625 | 0.039 | Synergism | PA82 | 4 | 250 | 0.25/15.625 | 0.125 | Synergism |
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MIC: minimum inhibitory concentration; FICI: fractional inhibitory concentration index.
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