Table 3. Molecular analysis of 27 MRSA isolates with elevated linezolid MICs (≥8 µg/mL) using VITEK 2 (bioMérieux, Marcy-l'Étoile, France).
| Patient | Isolate No. | Results of molecular analysis of genes conferring linezolid resistance | |||
|---|---|---|---|---|---|
| Domain V of 23S rRNA (proportion)* | Peptidyl transferase center† | Transferable element | |||
| L3 (rplC) | L4 (rplD), L22 (rplV) | optrA, cfr, cfr(B) | |||
| A | 1 | - | Gly152Asp | - | - |
| B | 2 | - | Gly152Asp | - | - |
| 3 | - | Gly152Asp | - | - | |
| 4 | - | Gly152Asp | - | - | |
| 5 | - | Gly152Asp | - | - | |
| 6 | - | Gly152Asp | - | - | |
| C | 7 | - | Ser214Leu | - | - |
| D | 8 | - | - | - | - |
| E | 9 | - | - | - | - |
| F | 10 | - | Gly152Asp | - | - |
| G | 11 | - | - | - | - |
| H | 12 | - | Gly152Asp | - | - |
| 13 | - | Gly152Asp | - | - | |
| 14 | - | Gly152Asp | - | - | |
| 15 | - | Gly152Asp | - | - | |
| 16 | - | Gly152Asp | - | - | |
| I | 17 | - | Gly152Asp | - | - |
| J | 18 | - | Gly152Asp | - | - |
| K | 19 | - | Gly152Asp | - | - |
| L | 20 | - | Gly152Asp | - | - |
| 21 | - | Gly152Asp | - | - | |
| M | 22 | T2500A (2/5) | - | - | - |
| 23 | T2500A (2/5) | - | - | - | |
| 24 | T2500A (2/5) | - | - | - | |
| 25 | T2500A (2/5) | - | - | - | |
| O | 26 | - | Gly152Asp | - | - |
| 27 | - | Gly152Asp | - | - | |
*23S rRNA mutations (E. coli numbering) and the proportion of the total number of 23S rRNA copies with the detected mutation; †Ribosomal protein mutations (S. aureus numbering) detected in the peptidyl transferase center of the genes (rplC, rplD, and rplV).
Abbreviations: MRSA, methicillin-resistant Staphylococcus aureus; MIC, minimal inhibitory concentration; rRNA, ribosomal RNA; cfr, chloramphenicol-florfenicol resistance.