Table 3.

Bivariable analysis assessing the association between colonisation with S. aureus in the nares and/or oropharynx and participant demographics and risk factors

Risk factor	Number positive (%)	Total (N)	PR	95% CI	P-value
Adults (n = 174)
Age	—	177	0.98	0.97−1.002	0.082
Number of S. aureus positive environmental sites in the home
Zero	45 (36.8)	122	-ref-	-ref-	-ref-
One	11 (47.8)	23	1.34	1.07–1.66	0.009
Two	12 (66.7)	18	1.26	1.10–1.43	<0.001
Three	4 (80.0)	5	1.18	1.11–1.26	<0.001
Four	3 (75.0)	4	1.12	1.09–1.16	<0.001
Five	1 (50.0)	2	1.08	1.03–1.13	<0.001
Minors (n = 83)
Number of Children
One	0 (0)	1	-ref-	-ref-	-ref-
Two	3 (15)	19	1.68	0.83–3.41	0.150
Three	13 (35)	37	1.54	0.90–2.64	0.113
Four	13 (59)	22	1.39	1.01–1.91	0.041
Five	0 (0)	4	1.25	1.07–1.46	0.004
Number of S. aureus positive environmental sites in the home
Zero	12 (22)	53	-ref-	-ref-	-ref-
One	4 (44)	9	1.68	1.07–2.64	0.025
Two	4 (57)	7	1.53	1.08–2.18	0.018
Three	2 (50)	4	1.38	1.10–1.72	0.005
Four	6 (85)	7	1.24	1.09–1.41	<0.001
Five	2 (66)	3	1.14	1.04–1.25	0.006
Asthma
No	21 (30)	70	-ref-	-ref-	-ref-
Yes	8 (66)	12	2.18	1.15–4.15	0.017
NA	1 (100)	1	NA	NA	NA

PR, prevalence ratio.

For adults, PRs were adjusted for age and estimated at age = 43. For minors, PRs were adjusted for the age, gender and age by gender interaction. Estimates for PR are calculated at the values of gender = Female and age = 10. For all discrete numeric variables, PR estimates are calculated as each discrete value over the previous discrete value (i.e. Prevalence ratio for number of positive environmental sites = 2 was calculated as prevalence given positive environmental sites = 2/ prevalence given positive environmental sites = 1). For dichotomous variables, PR estimates are estimated for prevalence given yes over prevalence given no.