Table V.

Final logistic regression models of risk factors for antimicrobial resistance among fecal Escherichia coli of pigs on 47 farrow-to-finish farms

						95% Confidence limits (CI)
Model of resistance outcome (% resistance)	Management and antimicrobial use variables	Pig stage category	Route of medication	P	Odds ratio	Lower CI	Upper CI
Ampicillin (35.21)	Age group of pigs	N/Aa	N/A	0	3.21	2.33	4.43
	Tiamulin use in pigs	N/Sb	N/S	0.002	4.87	1.82	13.01
	Interaction: age group of pigsc tiamulin use on farms	N/S	N/S	0.0242	0.41	0.19	0.89
Carbadox (10.11)	Carbadox use on farms	N/A	N/S	0.009	6.48	1.6	26.23
	Injection of sows	N/A	N/A	0.008	5.72	1.57	20.83
	Lincomycin use on farms	N/A	N/S	0.0137	0.17	0.04	0.69
Cephalothin (3.19)	Age group of pigs	N/A	N/A	0.6298	0.89	0.54	1.46
	Tylosin use on farms	N/S	N/S	0.023	0.04	0.01	0.32
	Interaction: age group of pigsc tylosin use on farms	N/A	N/A	0	8.47	2.44	29.37
Chloramphenicol (10.96)	Age group of pigs	N/A	N/A	0	3.77	2.36	6.03
	Tetracycline use on farms	N/S	N/S	0.0493	0.33	0.11	1
	Tylosin use on farms	Finisher pigs	In-feed	< 0.0001	9.29	2.84	30.37
		Finisher pigs	In-feed and injection	< 0.0001	19.9	3.63	109.1
Kanamycin (9.57)	Use of penicillins on farms	Weaner pigs	Injection	0.0141	10.41	1.61	67.38
Neomycin (9.79)	Age group of pigs	N/A	N/A	0	2.29	1.51	3.46
	Use of penicillins on farms	Piglets	Injection	0.0340d	3.5	1.1	11.17
	Farm size	N/A	N/A	0.008	1	1	1
Spectinomycin (55.00)	Age group of pigs	N/A	N/A	0	3.76	2.71	5.23
	Use of penicillins on farms	N/S	N/S	0.3426d	1.71	−1.77	5.16
	Spectinomycin use on farms	N/S	N/S	0.0539	2.39	−1.01	5.82
	Interaction: age group of pigsc use of penicillins on farms	N/A	N/A	0.004	3.08	1.43	6.6
Streptomycin (32.02)	Age group of pigs	N/A	N/A	0.001	1.62	1.22	2.16
	Spectinomycin use on farms	N/S	N/S	0.0168	2.29	1.15	4.16
	Farm size	N/A	N/A	0.002	1	1	1
Sulfamethoxazole (58.51)	Age group of pigs	N/A	N/A	< 0.0001	3.47	2.45	4.88
	Use of sulfonamides on farms	Weaner pigs	In-feed	0.0344	2.95	1.08	7.11
Tetracycline (81.28)	Age group of pigs	N/A	N/A	< 0.0001	3.47	2.46	4.89
	Ceftiofur use on farms	N/S	N/S	0	6.12	2.14	17.51
	Tiamulin use on farms	Weaner pigs	In-feed	0.0342	3.45	1.1	10.86
Trimethoprim/	Age group of pigs	N/A	N/A	0	4.02	2.52	6.4
sulfamethoxazole (5.53)	Tiamulin use on farms	N/S	N/S	0.028	7.75	1.25	48.11

^aNot applicable.

^bNot significant.

^cDenotes interaction between explanatory variables.

^dWald’s standard errors used.