Table 1. Hazard ratios (HR) of broiler chickens’ colonization with ESBL- and pAmpC- producing E. coli in the four investigated groups (control group, increased litter, reduced stocking density (reduced stocking) and alternative breed) adjusted for interaction ‘animal and sampling time’.

Strain	Factor	p-value		HR (95% CI)
ESBL- E. coli	Group	< 0.001	Control (reference)	1
			Increased litter (3 kg/m2)	2.38 (1.49–3.82)
			Reduced Stocking (25 kg/m2)	0.18 (0.12–0.28)
			Alternative breed (Rowan x Ranger)	1.01 (0.66–1.56)
	Animal	< 0.001	Seeder (reference)	1
			Sentinel	0.11 (0.05–0.23)
	Sampling time	< 0.001	1 (reference)	1
			2	3.90 (1.68–9.10)
			3	6.46 (2.57–16.25)
			4	7.54 (2.91–19.54)
			5	6.49 (2.57–16.36)
			6	2.36 (1.06–5.26)
			7	1.82 (0.83–3.97)
			8	4.35 (1.83–10.34)
			9	5.58 (2.26–13.75)
			10	4.91 (2.03–11.87)
pAmpC- E. coli	Group	< 0.001	Control (reference)	1
			Increased litter (3 kg/m2)	4.58 (2.09–10.06)
			Reduced Stocking (25 kg/m2)	0.94 (0.50–1.78)
			Alternative breed (Rowan x Ranger)	1.25 (0.65–2.40)
	Animal	> 0.999	Seeder (reference)	not estimated
			Sentinel
	Sampling time	< 0.001	1 (reference)	1
			2	10.56 (1.29–86.71)
			3	not estimated
			4	not estimated
			5	not estimated
			6	3.41 (0.86–13.48)
			7	1.61 (0.53–4.93)
			8	1.01 (0.36–2.80)
			9	10.83 (1.31–89.49)
			10	2.00 (0.62–6.49)

95% CI = 95% confidence interval; sampling time: 1 = 24 h post inoculation, 2 = 72 h post inoculation, 3–5 = 2nd week of trial, 6–7 = 3rd week of trial, 8–9 = 4th week of trial, 10 = 5th week of trial.