Table 3.
Summary of time-kill and checkerboard assessments of different combinations in different bacteria (n = 8).
| Combination | [(FOS) + (MEM)] mg/L | 6-h Effect | 24-h Effect | 24-h log10 Killing ∆ 24 h | Checkerboard |
|---|---|---|---|---|---|
| Fosfomycin + Meropenem | Isolate Ab 3 | ||||
| 0.25 FOS + 0.02 MEM | (32, 2) | Synergy | None | >+2 | Growth |
| 0.25 FOS + 0.12 MEM | (32, 8) | Bactericidal | Bactericidal | >−5 | Synergy |
| 0.5 FOS + 0.01 MEM | (64, 0.5) | None | Bactericidal | >−5 | Growth |
| 0.5 FOS + 0.25 MEM | (64, 16) | Bactericidal | Bactericidal | −6 | Partial synergy |
| Fosfomycin + Amikacin | Isolate Ab 1 | ||||
| 0.5 FOS + 0.004 AK | (64, 8) | None | Synergy | −2 | Growth |
| Fosfomycin + Tigecycline | Isolate Ab 4 | ||||
| 0.5 FOS + 0.02 TGC | (64, 0.06) | None | Bactericidal | −3 | Partial synergy |
Abbreviation: FOS = fosfomycin, MEM = meropenem, TGC = tigecycline, AK = amikacin, Ab = A. baumannii, Bactericidal effect = ≥3 log10 reduction in CFU/mL after 24 h compared with the starting inoculum (0 h). Synergy = ≥2 log10 reduction in CFU/mL after 24 h compared with in the antibiotic alone. Difference (∆) in bacterial concentration in log10 CFU/mL at 24 h compared with the starting inoculum. Bactericidal effect (≥3 log10 reduction in CFU/mL after 24 h) and synergy (≥2 log10 reduction in CFU/mL at 24 h with the combination as compared with the most active single drug). Checkerboard FICI values of x ≤ 0.5 (synergism) and 0.5 < x < 1 (partial synergy).