Table 2.

Hazard ratio (95% CI) of time until colonization for experiments 1 (n = 53), 2: dose 10² (n = 29), and 3 (n = 40); broilers were challenged with CTX-M-1-Escherichia coli at day 0 in experiment 1, and at day 5 in experiments 2 and 3.

Experiment	Variable		HR2 (95% CI)
1	Isolator1	2 (101 – none, reference)	1
		3 (101 – CEP)	0.25 (0.09–0.72)
		4 (101 – CEP)	0.24 (0.08–0.68)
		5 (102 – none)	0.27 (0.09–0.76)
		6 (102 – CEP)	0.74 (0.25–2.20)
		7 (102 – CEP)	0.89 (0.29–2.71)
	Seeder or contact bird	Seeder (reference)	1
		Contact	0.67 (0.34–1.30)
	Body weight at day 0 (hatch)		0.99 (0.91–1.09)
	Body weight at day 21		1.00 (1.00–1.01)
	Sex	Male (reference)	1
		Female	0.91 (0.43–1.91)
2	Isolator1	5 (102 – none, reference)	1
		6 (102 – CEP)	0.08 (0.02–0.42)
		7 (102 – CEP)	3.71 × 10−3 (2.71 × 10−4–0.05)
	Seeder or contact bird	Seeder (reference)	1
		Contact	1.09 (0.40–2.98)
	Body weight at day 0 (hatch)		0.93 (0.800–1.09)
	Body weight at day 21		1.00 (0.99–1.00)
	Sex	Male (reference)	1
		Female	0.64 (0.25–1.60)
	Total E. coli (cfu/g feces) day 5		1.06 (0.64–1.74)
3	Isolator1	2 (102 – none, reference)	1
		6 (102 – SYN)	0.07 (0.01–0.39)
		7 (102 – SYN)	1.29 (0.39–4.28)
		8 (102 – SYN)	3.11 (0.97–10.05)
	Seeder or contact bird	Seeder (reference)	1
		Contact	0.43 (0.20–0.94)
	Body weight at day 0 (hatch)		1.03 (0.94–1.13)
	Body weight at day 21		1.00 (0.99–1.00)
	Total E. coli (cfu/g feces) day 5		1.18 (0.80–1.74)

Abbreviations: CEP, competitive exclusion product; HR, hazard ratio; SYN, selection of pre- and probiotics.

¹Isolator number, dose level of challenge (10¹ or 10²), and intervention (none, CEP, or SYN).

²HR, indicating the ratio between the hazard of colonization with CTX-M-1-E. coli in the mentioned group and the reference group. A ratio of <1 indicates a smaller hazard, and a ratio of >1 indicates a higher hazard.