TABLE 2.
In vitro MICsa of kibdelomycin and levofloxacin for quinolone-resistant Gram-positive strains
| Organism | Phenotype | Mutation(s) | MIC (μg/ml) |
|
|---|---|---|---|---|
| Kibdelomycin | Levofloxacin | |||
| S. aureus | Wild-type parent | None | 0.25 | 0.25 |
| S. aureus MS5935A | 1st-step mutant | grlA (S80F) | 0.5 | 1 |
| S. aureus MS5935B | 2nd-step mutant | grlA (S80F), gyrA (S84L) | 0.5 | 16 |
| S. aureus MS5935C | 3rd-step mutant | grlA (S80F), gyrA (S84L), grlA (E84K) | 0.5 | 64 |
| S. aureus MS5935D | 4th-step mutant | grlA (S80F), gyrA (S84L), grlA (E84K), gyrA (E88V) | 0.5 | >128 |
| S. pneumoniae IID553 | Wild-type parent | None | 0.5 | 1 |
| S. pneumoniae NC9971 | Quinolone resistant | parC (S79Y), gyrA (S81F) | 0.5 | 32 |
a
MICs were determined by the CLSI agar diffusion method. Similar results were obtained with quinolone-resistant strains generated from S. aureus parent strains MS5952, MS5867, and MR6009. The quinolone-resistant S. aureus mutants were selected sequentially from clinical isolate MS5935 (14). The quinolone-resistant S. pneumoniae strain was selected from strain IID553 (15).