Table 10.
Minimum inhibitory concentration (MIC) of antimicrobials for E. coli, S. aureus and S. uberis from acute mastitis in dairy cows
| Bacterial species | Antimicrobial agent | Susceptiblea | Intermediatea | Resistanta | MIC50 (μg/mL) | MIC90 (μg/mL) | |||
|---|---|---|---|---|---|---|---|---|---|
| n | % | n | % | n | % | ||||
| Escherichia coli (n = 280) | Amoxicillin/clavulanic acid | 273 | 97.5 | 4 | 1.4 | 3 | 1.1 | 4 | 8 |
| Cefalexin | 268 | 95.7 | 10 | 3.6 | 2 | 0.7 | 4 | 8 | |
| Cefapirin | 185 | 66.1 | 64 | 22.9 | 31 | 11.1 | 8 | 32 | |
| Ceftiofur | 280 | 100 | 0 | 0 | 0 | 0 | 0.25 | 0.5 | |
| Cefquinome | – | – | – | – | – | – | 0.03 | 0.06 | |
| Enrofloxacin | – | – | – | – | – | – | 0.03 | 0.03 | |
| Marbofloxacin | – | – | – | – | – | – | 0.03 | 0.06 | |
| Neomycin | – | – | – | – | – | – | 1 | 2 | |
| Tetracyclines | 239 | 85.4 | 1 | 0.4 | 40 | 14.3 | 2 | ≥ 4 | |
| Staphylococcus aureus (n = 250) | Penicillin G | 160 | 64 | – | – | 90 | 36 | 0.06 | 2 |
| Amoxicillin/clavulanic acid | 250 | 100 | – | – | 0 | 0 | 0.25 | 1 | |
| Cloxacillin | 250 | 100 | – | – | 0 | 0 | 0.25 | 0.5 | |
| Cefalexin | 248 | 99.2 | 2 | 0.8 | 0 | 0 | 2 | 4 | |
| Cefapirin | 250 | 100 | 0 | 0 | 0 | 0 | 0.25 | 0.25 | |
| Ceftiofur | 249 | 99.6 | 1 | 0.4 | 0 | 0 | 1 | 1 | |
| Cefquinome | – | – | – | – | – | – | 0.5 | 1 | |
| Enrofloxacin | – | – | – | – | – | – | 0.12 | 0.25 | |
| Marbofloxacin | – | – | – | – | – | – | 0.25 | 0.5 | |
| Erythromycin | 246 | 98.4 | – | – | 2 | 0.8 | 0.25 | 0.5 | |
| Neomycin | – | – | – | – | – | – | 0.5 | 1 | |
| Tetracyclines | 237 | 94.8 | – | – | 13 | 5.2 | 0.25 | 0.5 | |
| Streptococcus uberis (n = 282) | Penicillin G | 198 | 70.2 | 84 | 29.8 | 0 | 0 | 0.03 | 0.25 |
| Amoxicillin/clavulanic acid | 282 | 100 | 0 | 0 | 0 | 0 | ≤ 0.012 | 0.5 | |
| Cloxacillin | – | – | – | – | – | – | 0.5 | 4 | |
| Cefalexin | 282 | 100 | 0 | 0 | 0 | 0 | 0.5 | 0.5 | |
| Cefapirin | 282 | 100 | 0 | 0 | 0 | 0 | 0.06 | 0.5 | |
| Ceftiofur | 280 | 99.3 | 2 | 0.7 | 0 | 0 | 0.12 | 2 | |
| Cefquinome | – | – | – | – | – | – | 0.03 | 0.25 | |
| Enrofloxacin | – | – | – | – | – | – | 0.5 | 1 | |
| Marbofloxacin | – | – | – | – | – | – | 1 | 2 | |
| Erythromycin | 225 | 79.8 | 4 | 1.4 | 53 | 18.8 | 0.06 | 16 | |
| Neomycin | – | – | – | – | – | – | 64 | ≥ 64 | |
| Tetracyclines | 201 | 71.3 | 0 | 0 | 81 | 28.7 | 0.25 | 64 | |