TABLE 4.
Mean tetracycline MICs for E. coli, Salmonella, and Campylobacter after initiation of the intervention, by type of sample and intervention status, from isolates regrown from frozen stock
| Agent | Sample type | Intervention
|
Control
|
Kruskal-Wallis result
|
|||||
|---|---|---|---|---|---|---|---|---|---|
| No. of isolates | MIC (μg/ml)
|
No. of isolates | MIC (μg/ml)
|
||||||
| Mean | SD | Mean | SD | χ2 | P | ||||
| E. coli | Fecal | 578 | 55.2 | 19.8 | 834 | 57.8 | 14.4 | 1.1 | 0.2952 |
| Calf pen | 33 | 45.8 | 26.9 | 30 | 46.8 | 25.9 | 0.0 | 0.9604 | |
| Maternity pen | 32 | 9.9 | 17.7 | 41 | 21.0 | 26.7 | 3.5 | 0.0615 | |
| Salmonella | Fecal | 11 | 36.7 | 31.3 | 144 | 64.0 | 14.2 | 67.2 | <0.0001 |
| Calf pen | 4 | 4.0 | 0 | 6 | 44.0 | 31.0 | 4.0 | 0.0455 | |
| Maternity pen | 2 | 4.0 | 0 | 5 | 16.0 | 26.8 | 0.4 | 0.5271 | |
| Campylobacter | Fecal | 13 | 108.5 | 39.9 | 12 | 106.8 | 41.2 | 0.0 | 0.9130 |
| Calf pen | 0 | 1 | 4.0 | ||||||
| Maternity pen | 3 | 21.4 | 36.9 | 2 | 48.0 | 22.6 | 1.4 | 0.2386 | |