Table 2.
In vitro interaction between ASA and AMB as determined by the nonparametric methoda
| Drug combination (MIC) and strain | FICI |
ΔE model (%) |
||||
|---|---|---|---|---|---|---|
| Mean (range) | Interpretation | Mean (range) | ΣSyn (n) | ΣAnt (n) | Interpretation | |
| F/MIC-1 (MIC80) | ||||||
| CCA10 | 1.000 (0.750-1.000) | Ind | 0.9 (−0.4-2.6) | 119 (11) | –74 (9) | Ind |
| YEM30 | 0.625 (0.563-0.750) | Ind | 2.3 (1.2-3.4) | 162 (15) | –16 (3) | Syn (M) |
| ATCC 22019 | 0.500 (0.375-0.500) | Syn | 4.5 (2.8-6.3) | 276 (15) | –8 (1) | Syn (S) |
| BF/MIC-2 (MIC50) | ||||||
| CCA10 | 0.125 (0.125-0.188) | Syn | 15.3 (12.8-17.8) | 1,225 (51) | 0 (0) | Syn (SS) |
| YEM30 | 0.250 (0.188-0.313) | Syn | 10.8 (6.5-15.1) | 927 (21) | 0 (0) | Syn (SS) |
| ATCC 22019 | 0.156 (0.156-0.1888) | Syn | 10.8 (6.6-14.9) | 918 (22) | 0 (0) | Syn (SS) |
F, planktonic cells; BF, biofilm cells; Syn, synergism; Ant, antagonism; Ind, indifference; (M), moderate synergism; (S), strong synergism; (SS), super strong synergism. For the FICI model, synergy was defined as a FICI of <0.5, antagonism was defined as a FICI of >4.0, and indifference was defined as a FICI of >0.5 to 4 (i.e., no interaction). For the ΔE model, ΣSyn and ΣAnt were the sums of the percentages of all statistically significant synergistic and antagonistic interactions. Interactions with 100% statistically significant interactions were considered weak synergism, those with 100 to 200% were considered moderate, and those with >200% were considered strong.