Table 4.
Quantitative drug susceptibility testing for isoniazid, rifampicin, amikacin, and ofloxacin in the presence and absence of efflux inhibitors.
| Antibiotic | Quantitative susceptibility testing (μg/ml) | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Suscep. | INHR | RIFR | OFXR | Poly-DR | MDR | XDR | |||||||||||
| H37Rv | MtbPT3 | MtbPT4 | MtbPT5 | MtbPT6 | MtbBR1 | MtbBR2 | MtbBR3 | MtbBR4 | MtbBR5 | MtbPT7 | MtbBR6 | MtbPT8 | MtbPT9 | MtbPT10 | MtbPT11 | ||
| INH | No EI | 0.1 | 10 | 0.4 | – | – | – | 10 | 10 | 10 | 10 | 3 | 80 | 20 | 20 | 3 | 3 |
| +VP | 0.1 | 10 | 0.4 | – | – | – | 3 | 3 | 3 | 3 | 1 | 3 | 10 | 1 | 1 | 1 | |
| +TZ | 0.1 | 3 | 0.4 | – | – | – | 3 | 3 | 10 | 3 | 1 | 3 | 3 | 20 | 1 | 3 | |
| +CPZ | 0.1 | 3 | 0.4 | – | – | – | 1 | 10 | 10 | 3 | 1 | 3 | 3 | 1 | 1 | 1 | |
| RIF | No EI | 1 | – | – | 256 | 512 | – | 1 | 320 | 640 | 160 | 320 | 80 | 320 | 80 | 320 | 320 |
| +VP | 1 | – | – | 32 | 32 | – | <0.125 | 40 | 40 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | |
| +TZ | 1 | – | – | 256 | 32 | – | <0.125 | 80 | 320 | 40 | 320 | 80 | 320 | 20 | 320 | 320 | |
| +CPZ | 1 | – | – | 32 | 20 | – | <0.125 | 80 | 320 | 40 | 320 | 20 | 20 | 4 | 20 | 20 | |
| AMK | No EI | 1 | – | – | – | – | – | – | – | – | – | – | 320 | 40 | 4 | 640 | 640 |
| +VP | 1 | – | – | – | – | – | – | – | – | – | – | 320 | 1 | 4 | 640 | 640 | |
| +TZ | 1 | – | – | – | – | – | – | – | – | – | – | 320 | 1 | 4 | 640 | 640 | |
| +CPZ | 1 | – | – | – | – | – | – | – | – | – | – | 320 | 1 | 4 | 40 | 40 | |
| CAP | No EI | 2.5 | – | – | – | – | – | – | – | – | – | – | 5 | 25 | 25 | 25 | 50 |
| +VP | 2.5 | – | – | – | – | – | – | – | – | – | – | 5 | 25 | 25 | 5 | 5 | |
| +TZ | 2.5 | – | – | – | – | – | – | – | – | – | – | 2.5 | 25 | 25 | 5 | 25 | |
| +CPZ | 2.5 | – | – | – | – | – | – | – | – | – | – | 2.5 | 25 | 25 | 5 | 5 | |
| OFX | No EI | 1 | – | – | – | – | 32 | 10 | – | – | – | – | – | – | 10 | 10 | 10 |
| +VP | 1 | – | – | – | – | 16 | 2 | – | – | – | – | – | – | 10 | 10 | 10 | |
| +TZ | 1 | – | – | – | – | 16 | <1 | – | – | – | – | – | – | 10 | 10 | 10 | |
| +CPZ | 1 | – | – | – | – | 16 | <1 | – | – | – | – | – | – | 10 | 10 | 10 | |
The lowest concentration tested corresponds to the critical concentration for each antibiotic except for rifampicin testing for strain MtbBR2 (see Section Materials and Methods for details). Synergistic interactions are in bold; –, not done. AMK, amikacin; CAP, capreomycin; CPZ, chlorpromazine; EI, efflux inhibitor; INH, isoniazid; MDR, multidrug resistant; OFX, ofloxacin; RIF, rifampicin; TZ, thioridazine; VP, verapamil; XDR, extensively drug resistant.