Table 1.
Minimum inhibitory concentration (MIC) and fractional inhibitory concentration index (FICI) of antibiotics against three methicillin-resistant staphylococcus aureus strains.
| Strain | MIC | FICI | |||||
|---|---|---|---|---|---|---|---|
| LIN | FOS | LEV | RIF | LIN-FOS | LIN-LEV | LIN-RIF | |
| 154311 | 2 (S) | 64 (R) | 0.25 (S) | >128 (R) | 0.375 (synergism) |
0.25 (synergism) |
>1 (no interaction or antagonism) |
| 152898 | 2 (S) | 32 (R) | 0.25 (S) | >128 (R) | 0.5 (synergism) |
0.75 (no interaction) |
>1 (no interaction or antagonism) |
| 159228 | 2 (S) | 64 (R) | 0.25 (S) | >128 (R) | 0.375 (synergism) |
0.75 (no interaction) |
>1 (no interaction or antagonism) |
LIN: linezolid; FOS: fosfomycin; LEV: levofloxacin; RIF: rifampin
S: susceptible; R: resistant. MIC was according to CLSI standards: Clinical and Laboratory Standards Institute.
FICI = FICA + FICB = (MIC Acombiantion/MIC Aalone) + (MIC Bcombiantion/MIC Balone) = (MIC of drug A in combination/MIC of drug A alone) + (MIC of drug B in combination/MIC of drug B alone).
FICI values were interpreted as follows: synergy, FICI ≤ 0.5; no interaction, 0.5 < FICI ≤ 4.0; antagonism, FICI > 4.0.