Table 6. ORs for the most important determinants of livestock-associated MRSA positivity in 1,054 pooled pig samples from 32 farms (multivariable final model), the Netherlands, 2011–2013*.
Characteristic | No.† | OR (95% CI) | p value |
---|---|---|---|
Sampling time | |||
0 mo | 262 | 0.83 (0.48–1.43) | <0.001 |
6 mo | 290 | 2.05 (1.25–3.37) | |
12 mo | 259 | 1.96 (1.20–3.20) | |
18 mo |
243 |
Ref |
|
Age group | |||
Gilts | 212 | 1.08 (0.65–1.80) | <0.001 |
Finishers | 140 | 4.09 (2.30–7.25) | |
Suckling piglets | 212 | 3.87 (2.34–6.39) | |
Weaned piglets | 280 | 9.89 (5.96–16.39) | |
Sows |
210 |
Ref |
|
External supply of gilts‡ | |||
Open | 630 | 5.54 (1.56–19.27) | 0.008 |
Closed |
424 |
Ref |
|
Delivery room for materials | |||
Yes | 804 | 0.29 (0.13–0.62) | 0.001 |
No |
250 |
Ref |
|
Sows housed in stable groups | |||
Yes | 594 | 0.53 (0.29–0.96) | 0.038 |
No |
460 |
Ref |
|
Antimicrobial drug use, per 2-fold increase, log2 DDDA/Y |
1,054 |
1.22 (1.03–1.44) |
0.024 |
Use of cephalosporins | |||
Yes | 84 | 3.15 (1.47–6.74) | 0.003 |
No | 970 | Ref |
*Model fit: −2 log RSPL estimation = 5331.7. Multivariable final model after backward elimination of non-significant variables from a full model (online Technical Appendix Table 3, http://wwwnc.cdc.gov/EID/article/21/6/14-0706-Techapp1.pdf) containing the significant associations (p<0.05) presented in Table 5 (http://wwwnc.cdc.gov/EID/article/21/6/14-0706-T5.htm) for all farms, together with antimicrobial drug use, use of cephalosporins, sampling time, and age group of the pool. MRSA, methicillin-resistant Staphylococcus aureus; OR, odds ratio; DDDA/Y, defined daily dosages animal per year; Ref, reference category; RSPL, residual pseudo-likelihood. †Multiple variables had missing values in the full model reducing the number of observations in the final model. ‡Farms were defined as open when they received external supplies of gilts ≥1 time per year from at least 1 supplier and as closed when they received no external supply of gilts.