Antimicrobial use policy change in pre-weaned dairy calves and its impact on antimicrobial resistance in commensal Escherichia coli: a cross sectional and ecological study

Table 7 Multivariable models of the associations between antibiotic treatments, age and resistance class stratified by time

Time	Risk factors	Cross tabulations				Resistance classes (odds ratio & 95% CI)
Time	Risk factors	TET	XNL⁺	NAL⁺	CIP + NAL + XNL⁺	XNL⁺	NAL⁺	CIP + NAL + XNL⁺
Post	Enrofloxacin
	Untreated	70	42	21	22
	Treated	27	12	9	42	0.9 (0.4–2.2)	0.8 (0.3–2.2)	6.4 (2.4–16.9)
	Sulfonamide
	Untreated	25	9	4	2
	Treated	72	45	26	62	6.3 (1.9–20.5)	0.7 (0.1–4.8)	22.7 (4.0–127.3)
	β-lactams
	Untreated	43	23	5	13
	Treated	54	31	25	51	2.3 (0.8–6.0)	4.8 (1.2–19.5)	3.3 (1.1–9.8)
	Age
	29 - 80d	73	25	26	26
	1 - 28d	24	29	4	38	13.9 (4.5–43.3)	0.9 (0.2–4.8)	48.1 (14–165.3)
Transition	Enrofloxacin
	Untreated	46	32	38	34
	Treated	9	2	29	8	1.6 (0.3–9.7)	4.4 (1.7–11.1)	7.2 (1.7–30.1)
	Sulfonamide
	Untreated	1	13	0	5
	Treated	54	21	67	37	0.1 (0.01–1.2)	NA	0.5 (0.05–5.2)
	β-lactams
	Untreated	22	23	19	19
	Treated	33	11	48	23	1.2 (0.4–3.8)	1.2 (0.4–3.8)	2.0 (0.6–4.7)
	Age
	29 - 80d	46	7	55	12
	1 - 28d	9	27	12	30	13.4 (3.7–49.1)	2.2 (0.8–6.2)	31.8 (8.4–120.3)

NA not applicable because cell count is 0
OR and 95% confidence intervals that exclude the null value of 1 are highlighted in bold

ISSN: 1471-2180