Table 2. Antimicrobial susceptibility of Macrococcus caseolyticus and Staphylococcus aureus strains to β-lactams as determined by broth microdilution.
| Strain/plasmid | Characteristics | mec genes | MIC of β-lactam antibiotics (mg/L) |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PEN | OXA | TMC | FOX | CTX | CAZ | FEP | CBP | CRL | ETP | IPM | MEM | |||
| M. caseolyticus | ||||||||||||||
| CCUG 15606 T | Type strain | — | ≤0.25 | ≤0.25 | 32 | 1 | 0.5 | 4 | 0.5 | ≤0.125 | ≤0.125 | 0.25 | ≤0.12 | 0.06 |
| KM1352 | Field strain | — | ≤0.25 | 0.5 | 64 | 2 | 1 | 8 | 1 | ≤0.125 | 0.25 | 0.5 | ≤0.12 | 0.12 |
| IMD0819 | Field strain | mecD-mecR1m-mecIm | 8 | 128 | >128 | 64 | >64 | >128 | >32 | 2 | 1 | >2 | 8 | 4 |
| IMD0473 | Field strain | mecD-mecR1m-mecIm | 8 | >128 | >128 | 64 | >64 | >128 | >32 | 4 | 2 | >2 | 4 | 8 |
| KM0211 | Field strain | mecD-mecR1m-mecIm | 16 | >128 | >128 | 128 | >64 | >128 | >32 | 8 | 2 | >2 | >16 | 8 |
| IMD0819_20 | IMD0819 ΔmcRImecD-1 | — | ≤0.25 | ≤0.25 | 32 | 1 | 0.5 | 4 | 0.5 | ≤0.125 | ≤0.125 | 0.25 | ≤0.12 | 0.12 |
| IMD0819_33 | IMD0819 ΔmcRImecD-1-McCIIMD0819 | — | ≤0.25 | ≤0.25 | 32 | 1 | 0.5 | 4 | 0.5 | ≤0.125 | ≤0.125 | 0.25 | ≤0.12 | 0.12 |
| S. aureus | ||||||||||||||
| RN4220 | Recipient strain | — | ≤0.25 | ≤0.25 | ND | 2 | ND | ND | ND | 0.5 | 0.25 | ND | ND | ND |
| RN4220/pTSSCm | RN4220 with S. aureus-E. coli shuttle vector pTSSCm | — | ≤0.25 | ≤0.25 | 64 | 2 | 1 | 8 | 2 | 0.5 | 0.25 | 0.12 | ≤0.12 | 0.12 |
| RN4220/pTSSCm-D1 | RN4220 with mecD cloned into pTSSCm | mecD | 2 | 2 | >128 | 32 | 16 | 64 | 8 | 1 | 1 | 2 | 0.5 | 2 |
| RN4220/pTSSCm-D2 | RN4220 with mecD, mecR1m and mecIm cloned into pTSSCm | mecD-mecR1m-mecIm | 0.5 | 1 | >128 | 16 | 4 | 16 | 4 | 0.5 | 1 | 0.12 | ≤0.12 | 0.25 |
Abbreviations: PEN, benzylbenicillin; OXA, oxacillin; TMC, temocillin; FOX, cefoxitin; CTX, cefotaxime; CAZ, ceftazidime; FEP, cefepime; CBP, ceftobiprole; CRL, ceftaroline; ETP, ertapenem; IPM, imipenem; MEM, meropenem.