Table 3.
Logistic regression model of variables associated with the presence of S. enterica in samples collected from the floor(s) of commercial broiler chicken barns in Ontario during the rest period (n = 696 samples from 36 b; random effects for barn, visit, and floor; α = 0.05).
| Variable | OR | 95% CI | P value |
|---|---|---|---|
| Sanitation procedure1,2 | |||
| Dry cleaning (n = 312) | Referent | ||
| Wet cleaning (n = 48) | 0.33 | 0.002–59.53 | 0.674 |
| Disinfection (n = 336) | 5.67 | 0.35–91.46 | 0.221 |
| Sampling point1 | |||
| Baseline (n = 232) | Referent | ||
| 2 d After sanitation (n = 232) | 0.36 | 0.14–0.92 | 0.032 |
| 6 d After sanitation (n = 232) | 0.28 | 0.11–0.72 | 0.008 |
| Flooring type1 | |||
| Concrete (n = 432) | Referent | ||
| Wood (n = 264) | 0.41 | 0.15–1.11 | 0.078 |
| Sanitation procedure ∗ Floor type | |||
| Dry ∗ Concrete (n = 192) | Referent | ||
| Wet ∗ Wood (n = 12) | 53.00 | 4.96–566.75 | 0.001 |
| Disinfection ∗ Wood (n = 132) | 3.76 | 0.95–14.87 | 0.059 |
| Season3 | |||
| Fall (n = 216) | Referent | ||
| Winter/Spring (n = 324) | 0.02 | 0.001–0.35 | 0.008 |
| Summer (n = 156) | 0.30 | 0.009–9.36 | 0.489 |
| Variance components | Variance | SE | ICC4 |
|---|---|---|---|
| Barn | 12.10 | 6.17 | 0.76 |
| Visit | 0.54 | 0.54 | 0.79 |
| Floor | 3.61 × 10−34 | 2.38 × 10−17 | 0.79 |
Overall P value for the model: 0.0022.
Abbreviations: CI, confidence interval; OR, odds ratio; SE, significance of error.
Included regardless of significance because it was an a priori variable of interest.
Dry cleaning: dry cleaning only; wet cleaning: dry cleaning followed by wet cleaning; disinfection: dry cleaning followed by wet cleaning followed by disinfection.
Fall: September 21st to December 20th; winter: December 21st to March 20th; spring: March 21st to June 20th; summer: June 21st to September 20th.
ICC: intraclass correlation coefficient calculated using the latent variable technique (variance at sample-level = π2/3 = 3.29).