Table I.
Prevalences of resistance among fecal Escherichia coli isolates from healthy weaner and finisher pigs on 47 farrow-to-finish farms
| Number of isolates growing at different concentrations (μg/mL)a |
% Resistant
|
||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Antimicrobial | 0.125 | 1 | 4 | 8 | 16 | 30 | 32 | 64 | 80 | 512 | Weaners (n = 470) | Finishers (n = 470) | Combined |
| Amikacin | 0 | 0 | 0.0 | 0.0 | 0 | ||||||||
| Ampicillin | 331 | 44.68 | 25.74 | 35.21 | |||||||||
| Apramycin | 31 | 4.68 | 1.91 | 3.3 | |||||||||
| Carbadox | 95 | 16.17 | 4.04 | 10.11 | |||||||||
| Ceftiofur | 0 | 0.0 | 0.0 | 0 | |||||||||
| Ceftriaxone | 0 | 3 | 0.21 | 0.43 | 0.32 | ||||||||
| Cephalothin | 30 | 4.04 | 2.34 | 3.19 | |||||||||
| Chloramphenicol | 103 | 15.53 | 6.38 | 10.96 | |||||||||
| Ciprofloxacin | 0 | 0 | 0 | 0.0 | 0.0 | 0 | |||||||
| Cotrimoxazole | 52 | 8.51 | 2.55 | 5.53 | |||||||||
| Florfenicol | 3 | 0.64 | 0.0 | 0.32 | |||||||||
| Gentamicin | 7 | 1.06 | 0.43 | 0.74 | |||||||||
| Kanamycin | 90 | 12.34 | 6.81 | 9.57 | |||||||||
| Nalidixic acid | 4 | 0.64 | 0.21 | 0.43 | |||||||||
| Neomycin | 92 | 12.55 | 7.02 | 9.79 | |||||||||
| Nitrofurantoin | 39 | 5.74 | 2.55 | 4.15 | |||||||||
| Spectinomycin | 517 | 65.53 | 44.47 | 55 | |||||||||
| Streptomycin | 301 | 36.60 | 27.45 | 32.02 | |||||||||
| Sulfamethoxazole | 550 | 70.43 | 46.60 | 58.51 | |||||||||
| Tetracycline | 764 | 89.57 | 72.98 | 81.28 | |||||||||
| Tobramycin | 32 | 4.89 | 1.91 | 3.4 | |||||||||
a
Vertical lines in the table indicate breakpoint concentrations at which resistance was determined for each antimicrobial.