Table 3. Environmental contamination with a colonizing or clinical infection strain and intra-household transmission by case-control status.

	Case households		Control households
	(N  = 146)		(N  = 145)
	N	(%)	N	(%)	aORa	(95% CI)	P
Environmental contamination with a colonizing or clinical infection strain
Contaminated with a colonizing strain or the clinical infection strain	73	(50)	43	(30)	2.4	(1.5–3.9)	<.01
Contaminated with a colonizing strain	54	(37)	43	(30)	1.4	(0.9–2.3)	.17
Contaminated with the clinical infection strain	45	(31)
Contaminated with a colonizing strain and the clinical infection strain	26	(18)
Intra-household transmission
≥2 household members colonized with identical strains or ≥1non-index household member colonized with the clinical infection strain	55	(38)	26	(18)	3.1	(1.8–5.6)	<.01
≥2 household members colonized with identical strains	35	(24)	26	(18)	1.5	(0.8–2.8)	.17
≥1 non-index household member colonized with theclinical infection strain	36	(25)
≥2 household members colonized with identical strains and ≥1non-index household member colonized with the clinical infection strain	16	(11)

Abbreviations: aOR, adjusted odds ratio; CI, confidence interval.

a. Logistic regression was used to calculate adjusted OR’s and 95% CI’s, controlling for household size.