Table 6.
Parameters estimated by applying the sigmoid model to evaluate the antibacterial activity index for S. aureus at pH 7.4, 6.5, and 5.0 vs. erythromycin in the presence of EO.
| EO-ERY | ATCC 29213 | Sensitive strains | Resistant strains | ||||||
|---|---|---|---|---|---|---|---|---|---|
| pH | 7.4 | 6.5 | 5.0 | 7.4 | 6.5 | 5.0 | 7.4 | 6.5 | 5.0 |
| R | 0.99 | 0.99 | 1.00 | 0.99 | 0.99 | 0.99 | 0.99 | 0.99 | 1.00 |
| Emax (Log10 CFU/mL) | 10.69 | 7.62 | 7.38 | 10.79 | 7.94 | 8.08 | 13.85 | 8.26 | 5.12 |
| ⋎ | 0.64 | 1.35 | 3.89 | 1.27 | 1.99 | 1.61 | 0.39 | 1.19 | 1.87 |
| C50 (μg/mL) of ERY | 0.03 | 0.08 | 0.84 | 0.04a | 0.11a | 0.53b | 189.50c | 33.59d | 61.15e |
| E0 (Log10 CFU/mL) | 6.11 | 5.01 | 4.48 | 6.87 | 4.59 | 4.34 | 5.34 | 4.97 | 1.89 |
Sigmoid model. E0, E index in the absence of antimicrobials; Emax, maximum reduction in bacterial count; C50, concentration of erythromycin (in the presence of EO) necessary to achieve 50% of the maximum antibacterial effect; ⋎, sigmoidicity coefficient. Wild strains were grouped by minimal inhibitory concentration (MIC) similarity. Different lowercase letters between the pHs mean statistical differences (p < 0.05). Values without significant differences have the similar letter (a, b, c, d, e).