Table 4.
Antimicrobial resistance of 136 S. Infantis isolated from 58 commercial farms of 5 integrated broiler operations.
| Antimicrobial agents | No. of antimicrobial resistant S. Infantis isolates (%) |
||||||
|---|---|---|---|---|---|---|---|
| Environments |
Dead chickens |
Total |
|||||
| Prior to placement |
At the time of depletion |
Within 1 week old (n = 2) | At 4–5 weeks old (n = 30) | pESI-negative (n = 15) | pESI-positive (n = 121) | ||
| Dust (n = 3)1 | Dust (n = 40) | Feces (n=61) | |||||
| Amoxicillin-clavulanate | 0 (0.0) | 5 (12.5) | 1 (1.6) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 6 (5.0) |
| Ampicillin | 1 (33.3)b | 38 (95.0)a | 52 (85.2)a,b | 1 (50.0)d | 29 (96.7)c | 2 (13.3)B | 119 (98.3)A |
| Cefazolin | 1 (33.3)b | 38 (95.0)a | 50 (82.0)a,b | 1 (50.0)d | 29 (96.7)c | 0 (0.0)B | 119 (98.3)A |
| Cefepime | 0 (0.0) | 2 (5.0) | 2 (3.3) | 0 (0.0) | 4 (13.3) | 0 (0.0) | 8 (6.6) |
| Cefotaxime | 1 (33.3)b | 37 (92.5)a | 50 (82.0)a,b | 1 (50.0)d | 29 (96.7)c | 0 (0.0)B | 118 (97.5)A |
| Cefoxitin | 0 (0.0) | 7 (17.5) | 11 (18.0) | 0 (0.0) | 4 (13.3) | 1 (6.7) | 21 (17.4) |
| Chloramphenicol | 1 (33.3)b | 36 (90.0)a | 50 (82.0)a,b | 1 (50.0)d | 30 (100.0)c | 2 (13.3)B | 116 (95.9)A |
| Ciprofloxacin | 0 (0.0) | 3 (7.5) | 2 (3.3) | 0 (0.0) | 1 (3.3) | 0 (0.0) | 6 (5.0) |
| Gentamicin | 1 (33.3) | 24 (60.0) | 29 (47.5) | 1 (50.0) | 15 (50.0) | 0 (0.0)B | 70 (57.9)A |
| Imipenem | 0 (0.0) | 1 (2.5) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 1 (0.8) |
| Nalidixic acid | 3 (100.0) | 38 (95.0) | 56 (91.8) | 2 (100.0) | 30 (100.0) | 9 (60.0)B | 120 (99.2)A |
| Tetracycline | 1 (33.3)b | 37 (92.5)a | 48 (78.7)a,b | 1 (50.0)d | 30 (100.0)c | 0 (0.0)B | 117 (96.7)A |
| Trimethoprim/sulfamethoxazole | 1 (33.3) | 28 (70.0) | 37 (60.7) | 0 (0.0)d | 23 (76.7)c | 0 (0.0)B | 89 (73.6)A |
| MDR | 1 (33.3)b | 38 (95.0)a | 51 (83.6)a,b | 1 (50.0)d | 30 (100.0)c | 1 (6.7)B | 120 (99.2)A |
1
n = No. of S. Infantis isolated from 5 integrated broiler operations.
Values with different superscript letters (a, b or c, d) represent significant differences between environments or dead chickens, respectively, while subscript letters (A, B) represent significant differences between pESI-positive and pESI-negative S. Infantis (P < 0.05). Multidrug-resistance (MDR) was defined as resistance to 3 or more antimicrobial classes.