TABLE 3.
Interactions between DIHQ and metronidazole against C. difficile clinical isolates
| C. difficile strain | MIC (μg/ml) by drug treatment |
ΣFIC indexa | Interpretationb | |||
|---|---|---|---|---|---|---|
| Metronidazole |
DIHQ |
|||||
| Alone | Combined with DIHQ | Alone | Combined with metronidazole | |||
| ATCC BAA-1870 | 0.125 | 0.015 | 1 | 0.125 | 0.25 | SYN |
| ATCC 43255 | 0.125 | 0.015 | 1 | 0.25 | 0.375 | SYN |
| ATCC 9689 | 0.25 | 0.03 | 0.125 | 0.06 | 0.62 | ADD |
| ATCC 1801 | 0.25 | 0.03 | 4 | 1 | 0.37 | SYN |
| P11 | 0.25 | 0.03 | 0.5 | 0.125 | 0.37 | SYN |
| P19 | 0.5 | 0.06 | 0.5 | 0.06 | 0.24 | SYN |
| P30 | 0.5 | 0.06 | 1 | 0.06 | 0.185 | SYN |
| I6 | 0.25 | 0.03 | 2 | 0.125 | 0.188 | SYN |
| I9 | 0.125 | 0.015 | 0.06 | 0.06 | 1.125 | ADD |
a
ΣFIC, fractional inhibitory concentration summation.
b
An ΣFIC index of ≤0.5 is considered synergistic (SYN); an ΣFIC index of >0.5 to 1.25 is considered additive (ADD); an ΣFIC index of >1.25 to 4 is considered indifferent (IND); and an ΣFIC index of >4 is considered antagonistic.