Table 1. Distribution of L. monocytogenes-positive samples in four slaughterhouses in Québec, between October 2013 and February 2015.
| Characteristics | Number of samples | Number (%) of L. monocytogenes- positive samples | Odds ratiosa | |
|---|---|---|---|---|
| Estimates | P-valueb | |||
| Seasons | ||||
| Fall | 624 | 44 (7.1) | Not included in the final modelc | |
| Winter | 936 | 90 (9.6) | ||
| Spring | 468 | 52 (11.1) | ||
| Summer | 468 | 57 (12.2) | ||
| Slaugherhouses | ||||
| A | 624 | 58 (9.3) | 1.9 | 0.05 |
| B | 624 | 55 (8.8) | 1.8 | 0.08 |
| C | 624 | 98 (15.7) | 3.6 | <0.001 |
| D | 624 | 32 (5.1) | Ref | |
| Operation areas | ||||
| Lairage | 848 | 68 (8.0) | 1.5 | 0.55 |
| Slaughtering and bleeding | 288 | 10 (3.5) | Ref | |
| Dehairing and evisceration | 368 | 51 (13.9) | 5.7 | <0.001 |
| Chilling and hanging | 128 | 24 (18.8) | 5.5 | <0.01 |
| Cutting and deboning | 864 | 90 (10.4) | 3.5 | <0.001 |
| Contact of surfaces with carcasses or meat | ||||
| Yes | 912 | 86 (9.4) | Not included in the final modelc | |
| No | 1584 | 157 (9.9) | ||
| Type of surfaced | ||||
| Conveyor belt top side | 160 | 19 (11.9) | 2.7 | <0.01 |
| Conveyor belt bottom side | 160 | 21 (13.1) | 3.0 | <0.01 |
| Environment | 656 | 86 (13.1) | 3.0 | <0.001 |
| Machines | 256 | 27 (10.6) | 2.6 | <0.01 |
| Pens | 800 | 65 (8.1) | 4.0 | 0.04 |
| Materials | 464 | 25 (5.4) | Ref | |
Ref: Reference category used for odds ratios.
a Odds ratios from multi-level multivariable logistic regression model.
b P-value adjusted for multiple comparison (Tukey-Cramer).
c Rejected from the final multivariable model (P-value>0.05 during backward selection)
d Sites, machines and materials are described in S1 Table.