TABLE 1.
Selection of first- and second-step mutants
| Straina | MIC (μg/ml)
|
Frequency of mutation at:
|
Changes in:
|
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Trovafloxacin | Ciprofloxacin | Levofloxacin | Sparfloxacin | Pefloxacin | 2× the MIC | 4× the MIC | 8× the MIC | GrlA | GrlB | GyrA | GyrB | |
| Parent strain RN4220 | 0.015 | 0.25 | 0.125 | 0.063 | 0.25 | None | None | None | None | |||
| First-step mutants | ||||||||||||
| 4220-53T | 0.125 | 2 | 0.5 | 0.063 | 4 | 1.1 × 10−10 | 1.1 × 10−10 | <1.1 × 10−10 | Ser80 to Phe | None | None | None |
| 4220-54T | 0.125 | 2 | 0.5 | 0.063 | 4 | Ser80 to Tyr | None | None | None | |||
| 4220-55T | 0.063 | 2 | 0.5 | 0.063 | 4 | Ser80 to Tyr | None | None | None | |||
| 4220-56T | 0.125 | 2 | 0.5 | 0.063 | 4 | Ser80 to Phe | None | None | None | |||
| 4220-16C | 0.063 | 1 | 0.5 | 0.125 | 4 | Glu84 to Lys | None | None | None | |||
| 4220-19C | 0.125 | 2 | 1 | 0.125 | 4 | Ser80 to Phe | None | None | None | |||
| 4220-20C | 0.125 | 1 | 0.5 | 0.125 | 4 | Ser80 to Phe | None | None | None | |||
| 4220-57C | 0.063 | 2 | 0.5 | 0.063 | 4 | 3.1 × 10−7 | 3.0 × 10−8 | <4.6 × 10−9 | Glu84 to Lys | None | None | None |
| 4220-58C | 0.125 | 2 | 0.5 | 0.063 | 4 | Ser80 to Phe | None | None | None | |||
| 4220-5L | 0.063 | 2 | 0.5 | 0.125 | 4 | 3.0 × 10−7 | 3.2 × 10−8 | <1.4 × 10−9 | None | Pro451 to Gln | None | None |
| 4220-7L | 0.125 | 2 | 0.5 | 0.125 | 4 | Gly78 to Cys | None | None | None | |||
| 4220-9L | 0.125 | 2 | 0.5 | 0.125 | 4 | Ser80 to Phe | None | None | None | |||
| 4220-11L | 0.125 | 2 | 0.5 | 0.125 | 4 | Ser80 to Phe | None | None | None | |||
| 4220-1P | 0.125 | 2 | 0.5 | 0.125 | 4 | 1.03 × 10−7 | <4.4 × 10−9 | <4.4 × 10−9 | Ser80 to Phe | None | None | None |
| 4220-3P | 0.125 | 2 | 0.5 | 0.125 | 4 | Glu84 to Lys | None | None | None | |||
| 4220-5P | 0.125 | 2 | 0.5 | 0.125 | 4 | Ser80 to Phe | None | None | None | |||
| 4220-7P | 0.125 | 2 | 0.5 | 0.125 | 4 | Ser80 to Tyr | None | None | None | |||
| Second-step mutants | ||||||||||||
| 4220-16-3S | 0.25 | 8 | 8 | 8 | 32 | 3.5 × 10−8 | 3.3 × 10−8 | 2.1 × 10−8 | Glu84 to Lys | None | Ser84 to Leu | None |
| 4220-16-8S | 0.5 | 8 | 4 | 8 | 32 | Glu84 to Lys | None | Ser84 to Leu | None | |||
| 4220-16-10S | 0.25 | 8 | 8 | 4 | 32 | Glu84 to Lys | None | Glu88 to Lys | None | |||
| 4220-16-21S | 0.25 | 8 | 4 | 4 | 32 | Glu84 to Lys | None | Glu88 to Lys | None | |||
| 4220-19-1S | 1 | 8 | 4 | 8 | 32 | 1.6 × 10−8 | 1.3 × 10−8 | 1.8 × 10−8 | Ser80 to Phe | None | Ser84 to Leu | None |
| 4220-19-6S | 1 | 8 | 4 | 4 | 32 | Ser80 to Phe | None | Glu88 to Lys | None | |||
| 4220-19-12S | 1 | 8 | 4 | 8 | 32 | Ser80 to Phe | None | Ser84 to Leu | None | |||
| 4220-19-23S | 1 | 8 | 4 | 4 | 32 | Ser80 to Phe | None | Glu88 to Lys | None | |||
| 4220-20-48C | 1 | 8 | 4 | 4 | 32 | Ser80 to Phe | None | Ser84 to Leu | None | |||
a
The strain number followed by T, C, L, P, or S designates mutant selected with trovafloxacin, ciprofloxacin, levofloxacin, pefloxacin, or sparfloxacin, respectively. The first-step mutants were selected with trovafloxacin or perfloxacin at 2× the MIC for RN4220 or with ciprofloxacin or levofloxacin at 4× the MIC for RN4220.