TABLE 1 .
The tobramycin-resistant subpopulation exhibits increased cross-resistance to gentamicin but not other antimicrobials
| Direct comparison of strains |
MIC (µg/ml) of druga: |
||||||
|---|---|---|---|---|---|---|---|
| TOB | CST | RIF | TET | AMK | CHL | GEN | |
| Comparison 1 | |||||||
| VIR-O | 48 | 1 | 4 | 3 | 192 | 256 | 96 |
| hetR-O2 | 128 | 1 | 4 | 3 | 192 | >256 | 192 |
| Comparison 2 | |||||||
| VIR-O | 64 | 1 | 4 | 3 | 96 | 96 | 32 |
| hetR-O3 | 192 | 1 | 4 | 3 | 96 | 128 | 128 |
| Comparison 3 | |||||||
| AV-T | 48 | 1 | 4 | 2 | 128 | 256 | 96 |
| hetR-T1 | 256 | 1 | 4 | 2 | 128 | 192 | >256 |
| Comparison 4 | |||||||
| AV-T | 32 | 1 | 4 | 3 | 64 | 96 | 32 |
| hetR-T4 | 384 | 1 | 4 | 3 | 64 | 96 | 128 |
a
Abbreviations: TOB, tobramycin; CST, colistin; RIF, rifampin; TET, tetracycline; AMK, amikacin; CHL, chloramphenicol; GEN, gentamicin. MICs were measured after 16 (TOB, CST, RIF, and TET) or 5 (AMK, CHL, and GEN) h of growth at 37°C. MICs were determined using Etest strips. Direct comparisons between isolates were performed by inoculating two cultures at an optical density A600 of 0.1 along the same Etest strip. Two independent experiments were performed for each comparison to assess reproducibility; data from a single representative experiment are shown.