TABLE 1.
Description of the strains used in this work
| Strain | Characteristic(s) | MIC (mg/liter)a |
Spontaneous mutation frequency |
|||||
|---|---|---|---|---|---|---|---|---|
| ATM (S ≤ 1–R >16) | TOB (S ≤4–R >4) | 300 mg/liter RIF | ATM |
TOB |
||||
| 4× MIC | 16× MIC | 4× MIC | 16× MIC | |||||
| PAO1 | Wild-type | 2 | 1 | 3.2 × 10−9 | 1.57 × 10−7 | <10−9 | 4.22 × 10−9 | <10−9 |
| PAOMS | △mutS | 2 | 1 | 1.1 × 10−6 | 9.76 × 10−6 | 8.28 × 10−8 | 8.39 × 10−7 | <10−9 |
| PAOMA | △mucA | 2 | 1 | 6.2 × 10−9 | 1.69 × 10−7 | <10−9 | 2.25 × 10−9 | <10−9 |
| PAOMSA | △mutS-△mucA | 2 | 1 | 1.6 × 10−6 | 3.87 × 10−6 | <10−9 | 1.11−7 | <10−9 |
| 146-HSE | CF strain LES-1, MDR epidemic strain (ST146), hypermutable (△mutS)b | 2 | 4 | 1.1 × 10−6 | 4.2 × 10−5 | 2.4 × 10−6 | 2.4 × 10−5 | 4.7 × 10−6 |
| 1089-HSE | CF strain derived from ST274 epidemic clone (ST1089), hypermutable (△mutS)b | 2 | 4 | 2.2 × 10−6 | 2.8 × 10−6 | 8.8 × 10−8 | 9.2 × 10−7 | 1.2 × 10−8 |
a
S, susceptible; R, resistant.
b
Strain 146-HSE shows a nonsynonymous (G778D) mutation in mutS not present in a preceding isogenic nonhypermutable isolate recovered from the same patient. Strain 1089-HSE shows a previously characterized inactivating mutation (4-bp deletion from nucleotide 814) in mutS (18).