TABLE 5.
Mean and median farm prevalence of blaCTX-M-positive E. coli strains according to farm-level characteristics
| Characteristic | No. of farms | Farm prevalence of blaCTX-M-positive E. coli strains |
Wilcoxon 2-sample P value | |
|---|---|---|---|---|
| Mean (SEM) | Median (range) | |||
| Region | ||||
| Northwest Washington | 9 | 0.439 (0.121) | 0.487 (0.822) | |
| Eastern Washington | 21 | 0.718 (0.063) | 0.822 (0.930) | 0.03 |
| No. of adult cows in the herd | ||||
| <3,000 | 19 | 0.551 (0.081) | 0.714 (1.0) | |
| ≥3,000 | 11 | 0.779 (0.076) | 0.860 (0.822) | 0.04 |
| Any animal movements onto the farm | ||||
| Yes | 11 | 0.824 (0.046) | 0.86 (0.442) | |
| No | 19 | 0.525 (0.083) | 0.714 (1.0) | 0.03 |
| Frequency of adding fresh bedding to calf hutches | ||||
| ≥weekly | 5 | 0.295 (0.703) | 0.178 (0.714) | |
| <weekly | 25 | 0.703 (0.059) | 0.8 (1.0) | 0.02 |
| Use of residual fly sprays | ||||
| No | 17 | 0.774 (0.045) | 0.822 (0.692) | |
| Yes | 13 | 0.452 (0.111) | 0.511 (1.0) | 0.04 |