Table 1.
Minimum inhibitory concentration for medically important antimicrobials, according to the WHO, of 593 Escherichia coli isolated from calf or cow feces or manure pit of 101 dairy farms in Québec Canada.
| Importance for human medicine† | Antimicrobial Class | Antimicrobial Agent | MIC (μg ml−1)* |
% resistant |
|||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.015 | 0.03 | 0.06 | 0.12 | 0.25 | 0.5 | 1 | 2 | 4 | 8 | 16 | 32 | 64 | 128 | 256 | 512 | ||||
| Critically important | Cephalosporin | Ceftiofur | 38.4 | 57.8 | 0.5 | 0.8 | -8,-515pt0.7 | 0.5 | 1.2 | 2.4 | |||||||||
| – Highest priority | 3rd generation | Ceftriaxone | 96.3 | 0.5 | 0.2 | -8,-515pt0.7 | 1.0 | 0.5 | 0.8 | 3.0 | |||||||||
| Quinolone | Ciprofloxacin | 97.3 | 1.3 | 0.3 | 0.2 | 0.8 | -8,-515pt | 0 | |||||||||||
| Danofloxacin | 99.0 | 0.3 | -8,-515pt0.5 | 0.2 | 0.7 | ||||||||||||||
| Enrofloxacin | 99.0 | 0.5 | -8,-515pt 0.3 | 0.2 | 0.5 | ||||||||||||||
| Nalidixic acid | 5.4 | 74.4 | 19.1 | 0.3 | 0.2 | 0.7 | 0.7 | ||||||||||||
| Macrolide | Azithromycin | 0.2 | 1.2 | 19.6 | 68.6 | 7.6 | 0.5 | 1.3 | 1.0 | 2.3 | |||||||||
| Critically important | Aminoglycoside | Gentamicin | 2.0 | 70.0 | 25.8 | 0.7 | -8,-515pt | 0.2 | 1.3 | 1.5 | |||||||||
| – High priority | Neomycin | 91.1 | 0.5 | 0.2 | 1.3 | 6.9 | 8.4 | ||||||||||||
| Streptomycin | 0.3 | 43.0 | 33.4 | 1.3 | 2.5 | 5.7 | 13.7 | 19.4 | |||||||||||
| Carbapenem | Meropenem | 99.7 | 0.3 | -8,-515pt | 0 | ||||||||||||||
| Amino/β-lac inh‡ | Amox.-CLA‡ | 2.4 | 17.4 | 63.1 | 14.2 | -8,-515pt 0.5 | 2.0 | 0.5 | 3.0 | ||||||||||
| Aminopenicillin | Ampicillin | 5.6 | 42.7 | 36.3 | 1.7 | -8,-515pt | 13.8 | 13.8 | |||||||||||
| Highly important | Cephamycin | Cefoxitin | 0.2 | 6.2 | 68.6 | 21.8 | -8,-515pt1.0 | 0.8 | 1.3 | 3.2 | |||||||||
| Folate pathway | Sulfisoxazole | 43.5 | 31.5 | 2.4 | 22.6 | 22.6 | |||||||||||||
| antagonist | TMP-sulfa§ | 81.5 | 5.4 | 0.7 | 0.2 | 12.3 | 12.3 | ||||||||||||
| Phenicol | Chloramphenicol | 0.8 | 26.0 | 62.6 | -8,-515pt 0.7 | 9.9 | 10.6 | ||||||||||||
| Florfenicol¶ | 0.2 | 5.9 | 68.5 | 16.7 | 8.8 | NA | |||||||||||||
| Tetracycline | Tetracycline | 74.4 | -8,-515pt 0.7 | 0.5 | 1.9 | 22.6 | 25.6 | ||||||||||||
| Important | Aminocyclitol | Spectinomycin | 4.4 | 75.9 | 9.4 | -8,-515pt 2.0 | 8.3 | 10.3 | |||||||||||
Numbers indicate percentages of isolates. White areas are concentrations of antimicrobials tested by the broth microdilution method. Percentages in gray areas have a MIC superior to the concentration range tested. Percentages in the first white area starting from left have MIC inferior or equal to the corresponding concentration. Dashed and plain lines represent threshold used to define intermediate and resistant clinical breakpoints, respectively. Intermediate and resistant isolates were grouped together and labeled as resistant for the last column of the table;
Importance of antimicrobials according to World Health Organization (15).
Penicillin + β-lactamase inhibitor: Amoxicillin/clavulanic acid combination;
Trimethoprim-sulfamethoxazole combination;
Florfenicol has no valid clinical breakpoints for Enterobacteriaceae and the concentration of 0.25 to 4μg mL−1 did not include the European epidemiological breakpoint of 16μg mL−1, thus no interpretation could be given.