Table 1.
MIC values for the different antibiotics used alone or in combination with pterostilbene against each of the tested bacterial isolates.
| Species | Source and mcr-1 confirmation | Antibiotics | MIC (μg/mL) | FIC Index | |
|---|---|---|---|---|---|
| Alone | Combination | ||||
| K. pneumoniae ZJ02 |
mcr-1-carrying K. pneumoniae from clinical infections in Zhejiang |
Colistin | 16.00 ± 0.00 | 1.33 ± 0.58 | 0.11 ± 0.04 |
| Cefalotin sodium | 1024.00 ± 0.00 | 1024.00 ± 0.00 | 1.03 ± 0.00 | ||
| Penicillin | 1024.00 ± 0.00 | 1024.00 ± 0.00 | 1.03 ± 0.00 | ||
| Imipenem | 2.67 ± 0.00 | 2.67 ± 0.00 | 1.03 ± 0.00 | ||
| Streptomycin | 512.00 ± 0.00 | 512.00 ± 0.00 | 1.03 ± 0.00 | ||
| Kanamycin | 1024.00 ± 0.00 | 1024.00 ± 0.00 | 1.03 ± 0.00 | ||
| Gentamycin | 512.00 ± 0.00 | 512.00 ± 0.00 | 1.03 ± 0.00 | ||
| Chloramphenicol | 512.00 ± 0.00 | 512.00 ± 0.00 | 1.03 ± 0.00 | ||
| Erythromycin | 256.00 ± 0.00 | 256.00 ± 0.00 | 1.03 ± 0.00 | ||
| Acheomycin | 213.33 ± 73.90 | 213.33 ± 73.90 | 1.20 ± 0.76 | ||
| K. pneumoniae ZJ05 |
mcr-1-carrying K. pneumoniae from clinical infections in Zhejiang |
Colistin | 26.67 ± 9.24 | 2.67 ± 1.15 | 0.14 ± 0.04 |
| Cefalotin sodium | 1024.00 ± 0.00 | 1024.00 ± 0.00 | 1.03 ± 0.00 | ||
| Penicillin | 1024.00 ± 0.00 | 1024.00 ± 0.00 | 1.03 ± 0.00 | ||
| Imipenem | 1.00 ± 0.00 | 1.00 ± 0.00 | 1.03 ± 0.00 | ||
| Streptomycin | 21.33 ± 9.24 | 21.33 ± 9.24 | 1.03 ± 0.00 | ||
| Kanamycin | 26.67 ± 9.24 | 26.67 ± 9.24 | 1.03 ± 0.00 | ||
| Gentamycin | 3.33.00 ± 1.15 | 2.67 ± 1.15 | 0.86 ± 0.29 | ||
| Chloramphenicol | 5.33 ± 2.31 | 5.33 ± 2.31 | 1.03 ± 0.00 | ||
| Erythromycin | 128.00 ± 0.00 | 128.00 ± 0.00 | 1.03 ± 0.00 | ||
| Acheomycin | 170.67 ± 73.90 | 170.67 ± 73.90 | 1.03 ± 0.00 | ||
| E. coli DH5α (pUC19-mcr-1) | Laboratory strain (carried a mcr-1 gene that originated from K. pneumoniae ZJ05) |
Colistin | 13.33 ± 4.62 | 2.00 ± 0.00 | 0.20 ± 0.07 |
| Cefalotin sodium | 256.00 ± 0.00 | 256.00 ± 0.00 | 1.03 ± 0.00 | ||
| Penicillin | 512.00 ± 0.00 | 512.00 ± 0.00 | 1.03 ± 0.00 | ||
| Imipenem | 0.25 ± 0.00 | 0.25 ± 0.00 | 1.03 ± 0.00 | ||
| Streptomycin | 2.00 ± 0.00 | 2.00 ± 0.00 | 1.03 ± 0.00 | ||
| Kanamycin | 2.67 ± 1.15 | 2.67 ± 1.15 | 1.03 ± 0.00 | ||
| Gentamycin | 1.67 ± 0.58 | 1.67 ± 0.58 | 1.03 ± 0.00 | ||
| Chloramphenicol | 4.00 ± 0.00 | 4.00 ± 0.00 | 1.03 ± 0.00 | ||
| Erythromycin | 16.00 ± 0.00 | 16.00 ± 0.00 | 1.03 ± 0.00 | ||
| Acheomycin | 1.00 ± 0.00 | 1.00 ± 0.00 | 1.03 ± 0.00 | ||
| E. coli DH5α (pUC19) | Laboratory strain (Polymyxin-sensitive mcr-1-negative) |
Colistin | 0.83 ± 0.29 | 0.67 ± 0.89 | 0.86 ± 0.29 |
| Cefalotin sodium | 256.00 ± 0.00 | 256.00 ± 0.00 | 1.03 ± 0.00 | ||
| Penicillin | 512.00 ± 0.00 | 512.00 ± 0.00 | 1.03 ± 0.00 | ||
| Imipenem | 0.25 ± 0.00 | 0.25 ± 0.00 | 1.03 ± 0.00 | ||
| Streptomycin | 2.00 ± 0.00 | 2.00 ± 0.00 | 1.03 ± 0.00 | ||
| Kanamycin | 2.00 ± 0.00 | 2.00 ± 0.00 | 1.03 ± 0.00 | ||
| Gentamycin | 1.67 ± 0.58 | 1.67 ± 0.58 | 1.03 ± 0.00 | ||
| Chloramphenicol | 4.00 ± 0.00 | 4.00 ± 0.00 | 1.03 ± 0.00 | ||
| Erythromycin | 8.00 ± 0.00 | 8.00 ± 0.00 | 1.03 ± 0.00 | ||
| Acheomycin | 1.00 ± 0.00 | 1.00 ± 0.00 | 1.03 ± 0.00 | ||
| E. coli ZJ40 |
mcr-1-carrying K. pneumoniae from clinical infection in Zhejiang (mcr-1 located in chromosome) |
Colistin | 85.33 ± 36.95 | 3.33 ± 1.15 | 0.15 ± 0.05 |
| Polymyxin B | 53.33 ± 18.48 | 2.67 ± 1.15 | 0.18 ± 0.02 | ||
| K. pneumoniae-E8.31 | Polymyxin-resistant mcr-1-positive K. pneumoniae from chicken cloacae in Shandong |
Colistin | 21.33 ± 9.24 | 3.33 ± 0.00 | 0.20 ± 0.07 |
| Polymyxin B | 16.00 ± 0.00 | 2.67 ± 1.15 | 0.20 ± 0.07 | ||
| K. pneumoniae-L18 | Polymyxin-resistant mcr-1- positive K. pneumoniae from chicken cloacae |
Colistin | 13.33 ± 4.62 | 3.33 ± 1.15 | 0.28 ± 0.00 |
| Polymyxin B | 16.00 ± 0.00 | 2.67 ± 1.15 | 0.20 ± 0.07 | ||
| K. pneumoniae-13b5 | Polymyxin-resistant mcr-1- positive K. pneumoniae from chicken cloacae in Shanghai |
Colistin | 32.00 ± 0.00 | 3.33 ± 1.15 | 0.14 ± 0.04 |
| Polymyxin B | 26.67 ± 9.24 | 2.67 ± 1.15 | 0.14 ± 0.04 | ||
| K. pneumoniae−16ZJJ9-19BC | Polymyxin-resistant mcr-1-negative K. pneumoniae from chicken cloacae in Zhejiang |
Colistin | 32.00 ± 0.00 | 10.67 ± 4.62 | 0.36 ± 0.14 |
| Polymyxin B | 26.67 ± 9.24 | 10.67 ± 4.62 | 0.45 ± 0.14 | ||
| K. pneumoniae K7 | mcr-1-negative K. pneumoniae from clinical infection in Jilin | Colistin | 1.33 ± 0.58 | 1.33 ± 0.58 | 1.03 ± 0.00 |
| Polymyxin B | 2.00 ± 0.00 | 2.00 ± 0.00 | 1.03 ± 0.00 | ||
| K. pneumoniae ATCC700603 | Laboratory strain | Colistin | 0.67 ± 0.29 | 0.83 ± 0.29 | 1.36 ± 0.58 |
| Polymyxin B | 1.00 ± 0.00 | 1.00 ± 0.00 | 1.03 ± 0.00 | ||
All MICs were determined in triplicate. According to the best synergistic effect, pterostilbene was used at a concentration of 16 μg/mL for K. pneumoniae and 32 μg/mL for E. coli, except E. coli ZJ40 (4 μg/mL). The FIC values of all mcr-1-positive isolates were indicated in bold.