Table 5. Most relevant farm characteristics associated to MRSA in veal calves obtained from the multiple regression models during the study period in the 51 farms, the Netherlands 2010–2012.
| 1st production cycle: ORs for a pooled sample to be MRSA-positive | 2nd production cycle: ORs for an individual animal sample to be MRSA-positive | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Variable a | Category | N b | OR | 95% CI | P-value c | N b | OR | 95% CI | P-value c |
| Sampling time | Week 0 | 510 | 0.20 | 0.15–0.28 | <0.01 | 1408 | 0.09 | 0.07–0.12 | <0.01 |
| Week 12 | 510 | Ref. | - | - | 1404 | Ref. | - | - | |
| Origin of veal calves d | Just from the Netherlands | 160 | 2.36 | 0.78–7.11 | 0.13 | 361 | 3.63 | 0.93–14.20 | 0.06 |
| The Netherlands or neighbor country | 640 | 3.11 | 1.33–7.23 | 0.01 | 1738 | 7.07 | 2.58–19.40 | <0.01 | |
| Not neighbor country | 220 | Ref | - | - | 713 | Ref. | - | - | |
| Number of stables | 4 to 6 | 100 | 3.18 | 1.09–9.22 | 0.03 | NA | NA | NA | NA |
| 1 to 3 | 920 | Ref. | - | - | NA | NA | NA | NA | |
| Ventilation of stables | Mechanical | NA | NA | NA | NA | 2023 | 0.23 | 0.10–0.53 | <0.01 |
| Natural | NA | NA | NA | NA | 789 | Ref. | - | - | |
| Presence of free-ranging cats in the farm | Yes | 540 | 2.14 | 1.11–4.12 | 0.02 | 1495 | 2.25 | 1.01–5.02 | 0.05 |
| No | 480 | Ref | - | - | 1317 | Ref. | - | - | |
Multiple regression associations after backward elimination from 2 full models containing variables with p<0.2 in the univariate analysis (Table 4) for each of the production cycles. P-values <0.05 are in boldface. MRSA, methicillin resistant Staphylococcus aureus; Ref., reference category of the variable; NA, variable not retained in the final model.
a Presented variables comply with the following criteria in at least one study cycle: i) less than 10% missing observations; ii) more than 10% of observations in each of the categories of a variable; iii) p ≤ 0.10.
b Maximum number of observations: i) in first cycle n = 1020 pools (10 pools in 51 farms in 2 sampling moments); ii) in the second cycle n = 2812 animals (mean of 28 animals sampled per farm in 51 farms in 2 sampling moments).
c Wald p-value.
d Neighboring countries from which animals are imported: Luxemburg (8 farms), Belgium (11 farms) and Germany (29 farms). Not neighboring countries were mostly Poland (16 farms), Latvia (5 farms) and Lithuania (13 farms). Overall p = 0.03 in first cycle and p<0.01 in second cycle.