TABLE 4.
Logistic regression models for resistance of E. coli isolates to selected antimicrobials and the percentage of variation in resistance due to barn, pen, and samples
| Antimicrobiala | Model (logit)b | % of variation in resistance
|
||
|---|---|---|---|---|
| Barn | Pen | Sample | ||
| Ampicillin | Intercept only | 3.3 | 2.7 | 94.0 |
| Cephalothin* | −2.7 − 0.68(pulse-CTC) + 0.09(period 2) + 1.19(pulse-CTC*period 2) | 13.8 | 2.8 | 83.4 |
| Chloramphenicol* | −2.76 + 0.60(cont-tylosin) + 0.46(period 2) - 1.05(cont-tylosin*period 2) | 31.9 | 2.1 | 66.0 |
| Kanamycin | 0.14 − 1.13(period 2) | 9.5 | 1.8 | 88.7 |
| Streptomycin | 0.26 − 0.60(cont-CTC) − 1.29(period 2) + 1.01(cont-CTC*period 2) | ∼0.0 | 2.7 | 97.3 |
| Sulfamethoxazole | 0.22 − 1.066(period 2) | 14.4 | 2.0 | 83.6 |
a
*, only the interaction was significant at the 0.05 level. The main effects were kept in the model despite their lack of significance since their interaction was significant.
b
cont, continuous.