TABLE 3.
Percentage of E. coli isolates that were resistant to specific antimicrobials grouped by period and treatmenta
| Antimicrobial | Period | % Resistant isolates (SE)b
|
|||||
|---|---|---|---|---|---|---|---|
| Continuous tylosin (n1 = 126, n2 = 150) | Continuous CTC (n1 = 113, n2 = 126) | Pulse tylosin (n1 = 118, n2 = 150) | Pulse CTC (n1 = 121, n2 = 146) | No antimicrobial (n1 = 118, n2 = 128) | All isolates (n1 = 596, n2 = 700)c | ||
| Amoxicillin-clavulanic acid | 1 | 0.8 (0.7) | 3.5 (2.3) | 0.0 | 0.8 (0.5) | 0.0 | 1.0 (0.6) |
| 2 | 2.0 (0.5) | 0.0 | 2.0 (1.2) | 0.0 | 0.0 | 0.9 (0.4) | |
| Ampicillin | 1 | 33.3 (9.5) | 42.5 (4.9) | 39.8 (8.4) | 30.6 (8.3) | 45.8 (8.6) | 38.3 (4.0) |
| 2 | 30.7 (7.1) | 35.7 (6.5) | 32.7 (7.5) | 31.5 (5.6) | 27.3 (1.6) | 31.6 (2.8) | |
| Cefoxitin | 1 | 0.8 (0.7) | 2.6 (1.7) | 0.0 | 0.0 | 0.0 | 0.7 (0.5) |
| 2 | 1.3 (0.6) | 0.0 | 2.0 (1.2) | 0.0 | 0.0 | 0.7 (0.4) | |
| Ceftiofur | 1 | 0.0 | 0.9 (0.6) | 0.0 | 0.0 | 0.0 | 0.2 (0.2) |
| 2 | 0.7 (0.6) | 0.8 (0.8) | 0.0 | 0.0 | 0.8 (0.6) | 0.4 (0.2) | |
| Cephalothin | 1 | 5.6 (4.3) | 3.5 (2.3) | 8.5 (3.1) | 3.3 (0.5) | 7.6 (1.2) | 5.7 (1.3) |
| 2 | 6.0 (1.5) | 6.4 (5.4) | 10.7 (3.8) | 11.0 (4.9) | 3.9 (2.2) | 7.7 (1.9) | |
| Chloramphenicol | 1 | 10.3 (4.4) | 8.0 (1.8) | 9.3 (4.6) | 1.6 (1.6) | 5.1 (1.4) | 6.9 (1.6) |
| 2 | 6.0 (3.4) | 8.7 (5.8) | 12.0 (5.4) | 5.5 (2.9) | 10.2 (4.2) | 8.4 (2.1) | |
| Gentamicin | 1 | 6.4 (4.2) | 3.5 (1.5) | 1.7 (0.9) | 2.5 (0.9) | 2.5 (1.2) | 3.4 (1.0) |
| 2 | 2.0 (1.3) | 9.5 (4.2) | 6.0 (2.6) | 2.7 (1.2) | 6.2 (1.5) | 5.1 (1.3) | |
| Kanamycin | 1 | 64.3 (4.0) | 43.4 (3.7) | 65.2 (6.1) | 45.4 (5.5) | 48.3 (7.0) | 53.5 (3.6) |
| 2 | 28.0 (7.2) | 23.8 (9.0) | 35.3 (9.0) | 26.7 (8.8) | 20.3 (4.6) | 27.1 (3.7) | |
| Streptomycin | 1 | 56.4 (7.0) | 41.6 (5.7) | 56.4 (4.6) | 50.4 (2.5) | 64.1 (3.9) | 53.9 (3.1) |
| 2 | 25.3 (5.2) | 34.9 (5.8) | 34.7 (3.8) | 26.7 (5.4) | 17.2 (4.6) | 27.9 (2.6) | |
| Sulfamethoxazole | 1 | 72.2 (4.5) | 40.7 (8.3) | 62.7 (7.6) | 51.2 (1.9) | 49.2 (7.1) | 55.5 (4.2) |
| 2 | 38.0 (13.1) | 28.6 (11.1) | 40.0 (12.5) | 24.0 (5.8) | 18.8 (2.4) | 30.3 (4.9) | |
| Tetracycline | 1 | 98.4 (1.2) | 90.3 (1.3) | 98.3 (1.6) | 98.4 (1.2) | 95.8 (0.6) | 96.3 (1.0) |
| 2 | 98.7 (0.6) | 98.4 (1.1) | 96.7 (1.5) | 98.0 (2.0) | 94.8 (2.7) | 97.1 (0.8) | |
| Trimethoprim-sulfamethoxazole | 1 | 1.6 (0.6) | 1.8 (0.8) | 2.5 (1.8) | 2.5 (1.9) | 0.8 (0.9) | 1.8 (0.6) |
| 2 | 1.3 (0.8) | 1.6 (1.1) | 0.7 (0.6) | 1.4 (1.0) | 0.8 (0.8) | 1.1 (0.4) | |
a
Pansusceptible antimicrobials (amikacin, ceftriaxone, ciprofloxacin and nalidixic acid) were excluded from this table.
b
n1 and n2 represent the number of isolates in periods 1 and 2, respectively. For amikacin, only 592 and 685 isolates were tested in periods 1 and 2, respectively.
c
Only 594 isolates were tested for resistance to streptomycin in period 1.