TABLE 3.
Susceptibility of all strains and isolates to fluoroquinolones and dyes
| Agent and efflux inhibitora | MIC (μg/ml) forb: |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Wild-type strain |
FQDR isolates |
FQ-R isolates |
DR isolates |
S isolates |
|||||||
| M3 | M4 | R6 | Range | MIC90 | Range | MIC90 | Range | MIC90 | Range | MIC90 | |
| Cip | 1 | 1 | 0.5 | 2-64 | 16 | 1-64 | 8 | 0.25-0.25 | 0.25 | 0.25-0.5 | 0.25 |
| Cip + res | 0.5 | 0.5 | 0.5 | 0.5-32 | 4 | 0.5-64 | 4 | 0.5-0.5 | 0.5 | 0.25-1 | 0.5 |
| Cip + NaO | 1 | 1 | 0.1 | 0.12-64 | 8 | 0.12-32 | 2 | 0.5-0.5 | 0.5 | 0.12-1 | 0.5 |
| Nor | 4 | 8 | 4 | 16-64 | 32 | 16-32 | 32 | 4-4 | 4 | 2-4 | 4 |
| Nor + res | 2 | 4 | 2 | 1-16 | 8 | 2-16 | 8 | 1-1 | 1 | 1-2 | 1 |
| EtBr | 2 | 2 | 1 | 4-16 | 8 | 1-8 | 2 | 16-16 | 16 | 1-4 | 2 |
| EtBr + res | 0.5 | 0.3 | 0.3 | 0.12-0.5 | 0.5 | 0.12-4 | 0.5 | 0.5-0.5 | 0.5 | 0.06-0.5 | 0.25 |
| EtBr + NaO | 0.3 | 0.3 | 0.1 | 0.12-2 | 1 | 0.06-4 | 0.5 | 1-1 | 1 | 0.06-1 | 0.25 |
| Acr | 4 | 4 | 2 | 8-16 | 8 | 2-4 | 4 | 16-16 | 16 | 2-4 | 4 |
| Acr + res | 1 | 1 | 1 | 0.25-2 | 1 | 0.25-4 | 0.5 | 2-2 | 2 | 0.25-2 | 1 |
| Acr + NaO | 0.5 | 0.5 | 0.3 | 0.25-2 | 1 | 0.25-2 | 0.5 | 2-2 | 2 | 0.25-1 | 0.5 |
a
Cip, ciprofloxacin; Nor, norfloxacin; EtBr, ethidium bromide; Acr, acriflavine; res, reserpine; NaO, sodium orthovanadate.
b
FQDR, resistant to both fluoroquinolones and dyes (n = 15); FQ-R, resistant to fluoroquinolones alone (n = 24); DR, dye resistant (n = 2); S, susceptible to all agents (n = 16). MICs of each agent in the absence of an efflux inhibitor are highlighted in boldface.