TABLE 2.
Pertinent regression parameters (with confidence intervals [CI]) and statistical analysis of the dose-response curves illustrated in Fig. 1 (killing curves of ciprofloxacin and moxifloxacin in broth)a,b
| Antibiotic and strain | Antibiotic alone
|
Antibiotic plus 20-mg/liter reserpine
|
ANCOVA | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Emax (CI) (Δlog10 CFU) | EC50 (CI) (mg/liter) |
Cstatic
|
R2 | Emax (CI) (Δlog10 CFU) | EC50 (CI) (mg/liter) |
Cstatic
|
R2 | ||||
| mg/ liter | Multiple of MIC | mg/ liter | Multiple of MIC | ||||||||
| Ciprofloxacin | |||||||||||
| EGD | −3.28 (−4.47 to −2.10) a; A | 1.02 (0.34 to 3.07) a; A | 0.7 | 0.6 | 0.959 | −3.60 (−4.49 to −2.72) a; A | 1.35 (0.63 to 2.90) a; A | 0.8 | 0.7 | 0.981 | NS |
| CLIP21369 | −5.21 (−8.37 to −2.06) b; A | 10.3 (2.75 to 38.9) b; A | 4.8 | 1.0 | 0.963 | −4.19 (−5.12 to −3.26) b; B | 1.76 (0.85 to 3.63) a; B | 1.1 | 0.8 | 0.987 | P < 0.001 |
| Moxifloxacin | |||||||||||
| EGD | −3.74 (−4.44 to −3.04) a; A | 0.53 (0.23 to 1.19) c; A | 0.3 | 0.5 | 0.966 | −3.69 (−4.20 to −3.19) a; A | 0.70 (0.39 to 1.28) b; A | 0.3 | 0.5 | 0.981 | NS |
| CLIP21369 | −4.64 (−5.21 to −4.06) b; A | 0.55 (0.30 to 0.99) c; A | 0.3 | 0.5 | 0.979 | −4.81 (−5.11 to −4.51) c; A | 0.45 (0.32 to 0.61) c; A | 0.2 | 0.7 | 0.994 | NS |
Parameters are defined as follows: Emax, CFU decrease (in log10 units) at 5 h from the original inoculum, as extrapolated for antibiotic concentration = ∞; EC50, antibiotic concentration (mg/liter) causing a reduction of the inoculum halfway between initial (E0) and maximal (Emax) values, as obtained from the Hill equation (using a slope factor of 1); Cstatic, concentration (mg/liter or multiple of the MIC) as determined in the absence (antibiotic alone) or in the presence (antibiotic plus reserpine) of 20-mg/liter reserpine resulting in no apparent bacterial growth (number of CFU identical to the original inoculum), as determined by graphical intrapolation.
Statistical analyses: for analysis per column (one-way analysis of variance with Tukey test for multiple comparisons), values with different lowercase letters are significantly different from each other (P < 0.01); for analysis per row (unpaired, two-tailed t test between corresponding parameters for activity in the absence and in the presence of reserpine), values with different uppercase letters are significantly different from each other (P < 0.01); for global analysis of covariance (ANCOVA) with Tukey test for multiple comparison, curves are compared in the absence and in the presence of reserpine for each antibiotic toward each strain. NS, nonsignificant.