Table 1.
Zone of inhibition (mm) for the antimicrobial agents and catechin alone and in combination against E. coli isolates.
| Bacteria | Antimicrobials | Zone of Inhibition (ZI) (mm) | ||||
|---|---|---|---|---|---|---|
| ZI of Antimicrobials | ZI Breakpoints According to CLSI * | ZI of Catechin | ZI of Catechin in Combination with Antimicrobials | Outcome | ||
| Escherichia coli ATCC 25922 # | Rifampin | 7.42 ± 0.0 | R | 10.47 ± 0.0 | 16 ± 0.0 | Antagonism |
| Tetracycline | - | R | 10.4 ± 0.0 | Additive | ||
| Erythromycin | - | R | 10.0 ± 0.0 | Antagonism | ||
| Clindamycin | - | R | 10.45 ± 0.0 | Additive | ||
| Azithromycin | 10.95 ± 0.0 | R | 22.5 | Synergy | ||
| Vancomycin | - | R | 10.4 ± 0.0 | Additive | ||
| Gentamicin | 31.32 ± 0.0 | S | 35 ± 0.0 | Antagonism | ||
| Escherichia coli ATCC 8739 # | Rifampin | 17.24 ± 0.0 | I | 9 ± 0.0 | 26 ± 0.0 | Additive |
| Tetracycline | - | R | 9.1 ± 0.0 | Additive | ||
| Erythromycin | - | R | 8.8 ± 0.0 | Antagonism | ||
| Clindamycin | - | R | 9.0 ± 0.0 | Additive | ||
| Azithromycin | 15.15 ± 0.0 | S | 25 ± 0.0 | Synergy | ||
| Vancomycin | - | R | 9.5 ± 0.0 | Synergy | ||
| Gentamicin | 13.14 ± 0.0 | I | 22 ± 0.0 | Additive | ||
| Escherichia coli ATCC 43895 # | Rifampin | - | R | 11.8 ± 0.0 | 11.5 ± 0.0 | Antagonism |
| Tetracycline | - | R | 12.0 ± 0.0 | Synergy | ||
| Erythromycin | - | R | 11.5 ± 0.0 | Antagonism | ||
| Clindamycin | - | R | 11.45 ± 0.0 | Antagonism | ||
| Azithromycin | 6.03 ± 0.0 | R | 17 ± 0.0 | Synergy | ||
| Vancomycin | - | R | 11.8 ± 0.0 | Additive | ||
| Gentamycin | 13.6 ± 0.0 | I | 22 | Antagonism | ||
|
Escherichia coli
(isolate 1) |
Rifampin | 2.45 ± 4.2 | R | 12.27 ± 1.3 | 13.89 ± 3.6 | Antagonism |
| Tetracycline | 13.85 ± 2.5 | I | 28.58 ± 1.0 | Synergy | ||
| Erythromycin | 11.97 ± 7.9 | I | 25.04 ± 0.6 | Synergy | ||
| Clindamycin | 7.71 ± 8.7 | R | 22.19 ± 1.3 | Synergy | ||
| Azithromycin | 11.58 ± 3.2 | R | 24.8 ± 0.5 | Synergy | ||
| Vancomycin | 13.72 ± 7.2 | I | 26.43 ± 0.5 | Synergy | ||
| Gentamicin | 10.42 ± 5.6 | R | 23.58 ± 0.4 | Synergy | ||
|
Escherichia coli
(isolate 2) |
Rifampin | - | R | 13.92 ± 3.6 | 14.0 ± 0.0 | Additive |
| Tetracycline | 16.83 ± 1.0 | S | 31.5 ± 10.0 | Synergy | ||
| Erythromycin | 18.97 ± 3.5 | I | 33.1 ± 0.0 | Synergy | ||
| Clindamycin | 17.75 ± 0.4 | I | 31.5 ± 4.5 | Additive | ||
| Azithromycin | 12.60 ± 2.84 | I | 27.2 ± 0.5 | Synergy | ||
| Vancomycin | 17.87 ± 2.2 | S | 31.6 ± 0.9 | Additive | ||
| Gentamicin | 16.95 ± 0.3 | S | 30.7 ± 0.8 | Additive | ||
|
Escherichia coli
(isolate 3) |
Rifampin | - | R | 12.9 ± 2.4 | 9.0 ± 5.2 | Antagonism |
| Tetracycline | 12.35 ± 0.4 | I | 26.12 ± 0.2 | Synergy | ||
| Erythromycin | 16.19 ± 1.0 | I | 31.5 ± 2.1 | Synergy | ||
| Clindamycin | 15.37 ± 3.8 | I | 28.2 ± 3.1 | Additive | ||
| Azithromycin | 12.43 ± 2.2 | I | 26.3 ± 0.3 | Synergy | ||
| Vancomycin | 18.87 ± 0.0 | S | 32.0 ± 0.7 | Synergy | ||
| Gentamicin | 16.24 ± 1.3 | S | 29.0 ± 0.1 | Additive | ||
|
Escherichia coli
(isolate 4) |
Rifampin | 10.87 ± 0.0 | R | 13.09 ± 0.0 | 20.21 ± 1.6 | Antagonism |
| Tetracycline | 15.26 ± 0.5 | S | 30.0 ± 1.6 | Synergy | ||
| Erythromycin | 20.61 ± 4.0 | I | 34.0 ± 0.0 | Synergy | ||
| Clindamycin | 16.42 ± 1.1 | I | 29.5 ± 1.2 | Additive | ||
| Azithromycin | 12.42 ± 0.7 | I | 26.1 ± 0.5 | Synergy | ||
| Vancomycin | 20.03 ± 5.2 | S | 25.5 ± 0.1 | Additive | ||
| Gentamicin | - | R | 13.1 ± 2.4 | Additive | ||
|
Escherichia coli
(isolate 5) |
Rifampin | - | R | 10.68 ± 5.6 | 10.71 ± 1.1 | Additive |
| Tetracycline | 16.82 ± 2.3 | S | 30.23 ± 0.0 | Synergy | ||
| Erythromycin | 16.5 ± 0.0 | I | 28.0 ± 4.4 | Synergy | ||
| Clindamycin | - | R | 12.1 ± 3.3 | Synergy | ||
| Azithromycin | 12.12 ± 1.5 | I | 24.0 ± 0.8 | Synergy | ||
| Vancomycin | 17.71 ± 3.4 | S | 29.0 ± 0.3 | Synergy | ||
| Gentamicin | - | R | 11.0 ± 0.2 | Synergy | ||
|
Escherichia coli
(isolate 6) |
Rifampin | - | R | 9.93 ± 3.6 | 9.0 ± 4.5 | Additive |
| Tetracycline | 12.26 ± 1.0 | I | 25.0 ± 0.0 | Synergy | ||
| Erythromycin | 14.1 ± 0.6 | I | 25.0 ± 0.0 | Synergy | ||
| Clindamycin | - | R | 10.5 ± 0.0 | Synergy | ||
| Azithromycin | 12.31 ± 2.6 | I | 23.2 ± 0.4 | Synergy | ||
| Vancomycin | 16.82 ± 0.5 | I | 27.0 ± 0.5 | Synergy | ||
| Gentamicin | 11.45 ± 0.0 | R | 21.8 ± 0.3 | Synergy | ||
|
Escherichia coli
(isolate 7) |
Rifampin | - | R | 12.75 ± 5.6 | 14.74 ± 8.3 | Synergy |
| Tetracycline | 12.93 ± 0.2 | I | 27.3 ± 0.9 | Synergy | ||
| Erythromycin | 14.59 ± 1.4 | I | 28.1 ± 3.4 | Synergy | ||
| Clindamycin | - | R | 13.22 ± 0.2 | Synergy | ||
| Azithromycin | 12.94 ± 0.6 | I | 26.6 ± 0.9 | Synergy | ||
| Vancomycin | 18.21 ± 1.5 | S | 30.89 ± 0.6 | Additive | ||
| Gentamicin | 11.81 ± 0.0 | R | 25.6 ± 0.4 | Synergy | ||
|
Escherichia coli
(isolate 8) |
Rifampin | - | R | 10.08 ± 4.3 | 14.69 ± 0.8 | Synergy |
| Tetracycline | 12.12 ± 11.0 | I | 24.6 ± 5.3 | Synergy | ||
| Erythromycin | 17.73 ± 8.76 | I | 28.4 ± 0.0 | Synergy | ||
| Clindamycin | - | R | 11.54 ± 1.3 | Synergy | ||
| Azithromycin | 12.04 ± 5.6 | I | 23.1 ± 0.2 | Synergy | ||
| Vancomycin | - | R | 10.0 ± 3.4 | Additive | ||
| Gentamicin | 11.02 ± 7.0 | R | 22.0 ± 1.1 | Synergy | ||
|
Escherichia coli
(isolate 9) |
Rifampin | 9.46 ± 1.1 | R | 13.58 ± 2.3 | 23.1 ± 2.5 | Additive |
| Tetracycline | 13.46 ± 2.3 | I | 27.89 ± 6.8 | Synergy | ||
| Erythromycin | 19.09 ± 0.6 | I | 33.1 ± 0.5 | Synergy | ||
| Clindamycin | - | R | 14.0 ± 0.0 | Synergy | ||
| Azithromycin | 12.82 ± 0.0 | I | 27.0 ± 0.4 | Synergy | ||
| Vancomycin | - | R | 13.5 ± 0.6 | Additive | ||
| Gentamicin | 11.1 ± 0.0 | R | 26.4 ± 0.8 | Synergy | ||
|
Escherichia coli
(isolate 10) |
Rifampin | - | R | 12.9 ± 1.7 | 12.6 ± 1.3 | Additive |
| Tetracycline | 13.4 ± 0.5 | I | 27.0 ± 1.1 | Synergy | ||
| Erythromycin | 14.34 ± 4.1 | I | 28.5 ± 8.85 | Synergy | ||
| Clindamycin | 15.38 ± 3.2 | I | 30.0 ± 5.5 | Synergy | ||
| Azithromycin | 12.55 ± 8.5 | I | 26.4 ± 0.5 | Synergy | ||
| Vancomycin | - | R | 12.82 ± 0.9 | Additive | ||
| Gentamicin | 13.52 ± 6.1 | I | 27.2 ± 0.4 | Synergy | ||
|
Escherichia coli
(isolate 11) |
Rifampin | - | R | 10.38 ± 0.6 | 10.4 ± 0.5 | Additive |
| Tetracycline | 12.28 ± 0.0 | I | 24.5 ± 0.7 | Synergy | ||
| Erythromycin | - | R | 10.5 ± 1.4 | Additive | ||
| Clindamycin | 16.69 ± 1.1 | I | 28.1 ± 1.1 | Synergy | ||
| Azithromycin | 12.21 ± 0.9 | I | 22.5 ± 0.5 | Additive | ||
| Vancomycin | 16.59 ± 3.1 | I | 29.0 ± 0.7 | Synergy | ||
| Gentamicin | 13.76 ± 2.5 | I | 25.4 ± 1.1 | Synergy | ||
|
Escherichia coli
(isolate 12) |
Rifampin | 8.76 ± 5.3 | R | 13.17 ± 1.5 | 22.5 ± 6.4 | Synergy |
| Tetracycline | 18.34 ± 7.1 | I | 31.9 ± 0.5 | Synergy | ||
| Erythromycin | - | R | 13.4 ± 11.0 | Additive | ||
| Clindamycin | 15.71 ± 2.6 | I | 30.5 ± 0.0 | Synergy | ||
| Azithromycin | 12.77 ± 1.5 | I | 26.4 ± 0.2 | Synergy | ||
| Vancomycin | 15.24 ± 1.1 | I | 28.5 ± 0.4 | Additive | ||
| Gentamicin | 13.73 ± 0.6 | I | 27.5 ± 0.9 | Synergy | ||
|
Escherichia coli
(isolate 13) |
Rifampin | - | R | 13.18 ± 8.7 | 13.0 ± 0.0 | Additive |
| Tetracycline | 9.82 ± 4.3 | R | 25.4 ± 1.4 | Synergy | ||
| Erythromycin | - | R | 14.21 ± 0.0 | Synergy | ||
| Clindamycin | 18.27 ± 5.2 | I | 32.0 ± 0.5 | Synergy | ||
| Azithromycin | 12.67 ± 9.7 | I | 27.1 ± 0.0 | Synergy | ||
| Vancomycin | 16.37 ± 10.0 | I | 29.45 ± 0.5 | Additive | ||
| Gentamicin | 13.14 ± 8.7 | I | 27.2 ± 0.3 | Synergy | ||
|
Escherichia coli
(isolate 14) |
Rifampin | 7.67 ± 2.6 | R | 12.4 ± 1.3 | 20.0 ± 3.8 | Additive |
| Tetracycline | 10.22 ± 11.0 | R | 23.4 ± 1.5 | Synergy | ||
| Erythromycin | - | R | 12.42 ± 0.5 | Additive | ||
| Clindamycin | - | R | 13.1 ± 0.6 | Synergy | ||
| Azithromycin | 11.28 ± 5.4 | I | 23.5 ± 2.7 | Additive | ||
| Vancomycin | 16.24 ± 8.6 | I | 29.0 ± 0.4 | Synergy | ||
| Gentamicin | 11.81 ± 5.9 | I | 25.1 ± 0.2 | Synergy | ||
|
Escherichia coli
(isolate 15) |
Rifampin | - | R | 12.62 ± 6.6 | 12.5 ± 7.8 | Additive |
| Tetracycline | 15.89 ± 7.4 | S | 29.1 ± 0.0 | Synergy | ||
| Erythromycin | 9.42 ± 11.0 | R | 24.01 ± 11.6 | Synergy | ||
| Clindamycin | - | R | 14.0 ± 4.3 | Synergy | ||
| Azithromycin | - | R | 12.5 ± 0.9 | Additive | ||
| Vancomycin | 15.37 ± 8.3 | I | 28.0 ± 0.9 | Additive | ||
| Gentamicin | - | R | 13.2 ± 0.6 | Synergy | ||
“#” means statistical data are unavailable, “-” means no activity, and “*” indicates that the results are categorized according to Clinical and Laboratory Standards Institute (CLSI) guidelines into R resistant; I intermediately resistant; and S sensitive. All the data were obtained from three independent experiments and is expressed as mean ± SD.