TABLE 1.
Relative fitness of rifampin-resistant S. aureus in vitro mutants
| Strain | No. of independent isolates | rifampin MIC (μg/ml) | Amino acid change | Ratio of wild type/mutant
|
Relative fitness (mean ± SEM)a | |
|---|---|---|---|---|---|---|
| Initialb | Finalb | |||||
| Wild type | ≤0.008 | 1 | ||||
| Mutant 1 | 1 | 4 | 481His→Asn | 1.1 | 1.1 | 1 ± 0.004 |
| Mutant 2 | 1 | 4 | 471Asp→Tyr | 0.8 | 6.0 | 0.88 ± 0.012d |
| Mutant 3 | 1 | 0.5 | 471Asp→Glu | 1.2 | 2.1 | 0.96 ± 0.008d |
| Mutant 4 | 2 | 0.5 | 471Asp→Gly | 0.9 | 7.9 | 0.87 ± 0.022d |
| Mutant 5 | 3 | 4 | 527Ile→Phe | 0.7 | 2.2 | 0.93 ± 0.016d |
| Mutant 6 | 1 | 4 | 464Ser→Pro | 0.7 | 2.0 | 0.93 ± 0.008d |
| Mutant 7 | 2 | 8 | 474Asn→Lys | 0.7 | 298.0 | 0.60 ± 0.040d |
| Mutant 8 | 1 | 1 | 477Ala→Val | 0.7 | 5.0 | 0.88 ± 0.023d |
| Mutant 9 | 1 | 256 | 477Ala→Asp | 0.8 | 3.8 | 0.91 ± 0.013d |
| Mutant 10 | 3 | 256 | 484Arg→His | 0.5 | 34.0 | 0.75 ± 0.019d |
| Mutant 11 | 3 | 512 | 486Ser→Leu | 0.5 | 5.1 | 0.86 ± 0.011d |
| Mutant 12 | 1 | >512 | 468Gln→Arg | 0.8 | 20.1 | 0.80 ± 0.007d |
| Mutant 13 | 1 | 512 | 468Gln→Leu | 1.0 | 2.5 | 0.95 ± 0.016d |
| Mutant 14 | 5 | 512 | 481His→Tyr | 1.0 | 2.7 | 0.93 ± 0.011d |
| Mutant 15c | 1 | >512 | 481His→Asn, 482Lys→Asn | 0.8 | 1.9 | 0.94 ± 0.024d |
| Mutant 16c | 1 | 256 | 481His→Asn, 478Glu→Asp | 0.6 | 2.2 | 0.92 ± 0.019d |
| Mutant 17c | 1 | 256 | 481His→Asn, 477Ala→Thr | 0.7 | 1.2 | 0.98 ± 0.015 |
| Mutant 18c | 1 | >512 | 481His→Asn, 466Leu→Pro | 0.6 | 5.6 | 0.87 ± 0.036d |
a
Mean values and standard errors of the mean (SEMs) were derived from a total of four different fitness assays.
b
Mean values were derived from a total of four different fitness assays.
c
Mutant was obtained by culturing mutant 1 on agar containing 10 μg of rifampin per ml.
d
The fitness reduction is significant, as determined by the one-sample t test (P < 0.05).