TABLE 1.
Characteristics of strains of M. smegmatisa
| Strain | Characteristic (reference) | InhA mutation | Relative MIC (SD)b of:
|
||
|---|---|---|---|---|---|
| Triclosan
|
Isoniazid in 7H9 | ||||
| In LB | In 7H9 | ||||
| mc2155 | Wild type (see reference 12) | None | 1.0 | 1.0 | 1.0 |
| MT1 | mc2155 selected on triclosan (this work) | M161V | 4.9 (0.9) | 6.3 (2.0) | 8.5 (2.5) |
| MT9 | mc2155 selected on triclosan (this work) | M103T | 4.4 (1.1) | 6.3 (2.0) | 1.2 (0.5) |
| MT17 | mc2155 selected on triclosan (this work) | A124V | 4.0 (1.2) | 5.8 (1.7) | 2.0 (0.7) |
| mc2651 | mc2155 selected on isoniazid (3) | S94A | 4.4 (1.3) | 6.3 (2.0) | 22 (12) |
| mc2155/pMD31::inhA+ | mc2155 bearing multicopy inhA+ (see text) | None | 4.6 (0.6) | 6.3 (2.0) | >64 |
All MICs were determined on agar plates by twofold serial dilutions using logarithmic-phase cells as described elsewhere (12). Cells were grown with 0.05% Tween 80 either in LB broth or in 7H9 medium supplemented with Middlebrook ADC enrichment (Difco) plus 0.2% glycerol and were tested on the corresponding solid medium without Tween 80. All plates with triclosan also contained 0.1% ethanol. Less clumping of cells during growth was seen in 7H9 than in LB, but the MIC for mutants on 7H9 agar approached the solubility limit of triclosan in this medium (50 to 100 μg ml−1, observed visually).
Results are means (± standard deviations) from four to five experiments. MICs are expressed as ratios to the MICs for mc2155. MICs for mc2155 are as follows (in micrograms per milliliter): triclosan in LB, 0.61 ± 0.15; triclosan in 7H9, 14 ± 5; isoniazid in 7H9, 7 ± 2.