Cohort description: The Danish Blood Donor Staphylococcus aureus Carriage Study

Figures & data

Figure 1 Flowchart of the Danish Blood Donor S. aureus Carriage Study cohort.

Table 1 Characteristics of the DBDSaCS cohort (n=6082) in comparison with the national blood donor cohort (n=234,836)

	DBDSaCS^a		Blood donors not participating^a
	Women	Men	Women	Men
N (%)	2683 (44.1)	3399 (55.9)	126,738 (54.0)	108,098 (46.0)
Age, years	36.7 (25.7–50.2)	39.1 (28.5–50.9)	34.6 (24.6–48.0)	39.5 (28.0–51.1)
Age strata (%)
18–25	21.6	12.3	26.5	16.8
26–35	26.0	29.3	24.2	24.0
36–45	17.5	21.7	18.9	20.9
46–55	19.2	19.8	18.1	21.3
56–67	15.7	17.0	12.4	17.1
Hemoglobin, mmol/L	8.5 (8.2–8.8)	9.4 (9.1–9.7)	8.5 (8.1–8.8)	9.4 (9.1–9.8)
Donations during previous:
1 year	2 (2–3)	3 (2–4)	2 (1–3)	2 (1–3)
3 years	5 (4–7)	6 (4–9)	3 (1–5)	4 (2–7)
5 years	7 (5–10)	9 (6–12)	4 (2–8)	7 (3–11)
Weight, kg	70 (63–80)^b	84 (76–93)^b	NA	NA
Height, cm	170 (165–174)^c	183 (178–187)^c	NA	NA
BMI, kg/m^2	24.3 (22.1–27.5)^d	25.2 (23.3–27.4)^d	NA	NA
Current smoker (%)	11.8^e	12.6^e	NA	NA
Short form-12
Physical Component Score	56.6 (53.8–57.8)^f	56.6 (54.1–57.9)^f	NA	NA
Mental Component Score	55.1 (51.2–57.7)^f	55.8 (52.8–57.7)^f	NA	NA

Notes: Results are reported as medians (interquartile ranges) and numbers (percentages). ^aThe DBDSaCS cohort includes blood donors from Central Denmark Region and North Denmark Region compared with blood donors from all five regions of Denmark not participating. ^b=49 missing values; ^cn=87 missing; ^dn=91 missing; ^en=46 missing values; ^fn=45.

Abbreviations: DBDSaCS, the Danish Blood Donor S. aureus Carriage Study; BMI, body mass index.

Figure 2 Bar chart illustrating the number of participants included by calendar month and their carrier status. Orange (or lower pillar) = S. aureus positive; Green (or upper pillar) = S. aureus negative.

Table 2 Samples and data collected in DBDSaCS

	No. of samples/measurements	Material
Baseline plasma samples	12,164	5 mL EDTA plasma from the first inclusion in DBDSaCS
Follow-up plasma samples	4180	5 mL EDTA plasma from follow-up in DBDSaCS
Baseline nasal swabs	6082	Nasal swabs from anterior nares, both nostrils
Follow-up nasal swabs, 2nd visit	1385	Nasal swabs from anterior nares, both nostrils
Follow-up nasal swabs, 3rd visit	459	Nasal swabs from anterior nares, both nostrils
Follow-up nasal swabs, 4th visit	165	Nasal swabs from anterior nares, both nostrils
Follow-up nasal swabs, 5th visit	76	Nasal swabs from anterior nares, both nostrils
Throat swabs	262	Throat swabs from oropharynx and both tonsils
S. aureus isolates	3465	S. aureus isolates after culturing from positive nasal and throat swabs
Questionnaire data, DBDSaCS	8067	Anthropometric, health-related quality of life, smoking, and physical activity data
Questionnaire data, DBDS version 2	4488	Asthma, allergy, upbringing, and screening questions of hidradenitis suppurativa
Immunological markers
Complete blood count	7886	Hemoglobin, white blood cells, hemotocrit, platelets,
Leukocyte subsets	6742	Blood cell counts of basophil, eosinophil, lymphocytes, monocytes, and neutrophil
Ferritin	724	Marker of iron metabolism
Genetics	3133	Approx. 650,000 single nucleotide polymorphisms
Nasal microbiome	2161	Nasal microbiome characterization using 16S rRNA gene-based sequencing
Danish registers linkage	6082	Entire cohort linked to NPR, DNPR, and socioeconomic data at Statistics Denmark

Abbreviations: DBDSaCS, the Danish Blood Donor S. aureus Carriage Study; NPR, the Danish National Patient Register; DNPR, the Danish National Prescription Register.

Table 3 Characteristics of the DBDSaCS cohort by carrier status (n=6082)

	Total	S. aureus-positive	S. aureus-negative
N (%)	6082	2488 (41)	3594 (59)
Age, years	38.1 (26.9–50.6)	36.6 (26.5–49.0)	39.3 (27.5–51.3)
18–25	997 (16)	442 (44)	555 (56)
26–35	1693 (28)	729 (43)	964 (57)
36–45	1206 (20)	505 (42)	701 (58)
46–55	1189 (20)	460 (39)	729 (61)
56–67	997 (16)	352 (35)	645 (65)
Women	2683 (44)	924 (34)	1759 (66)
Men	3399 (56)	1564 (46)	1835 (54)
Weight, kg^a	79 (70–89)	80 (71–90)	78 (69–88)
Height, cm^b	177 (170–184)	178 (172–185)	176 (170–183)
BMI, kg/m^2 c	24.9 (22.7–27.5)	25.1 (22.9–27.8)	24.8 (22.6–27.2)
BMI, categorized (kg/m2)^c
BMI<18.5, underweight (%)	26 (0.4)	12 (0.5)	14 (0.4)
18.5≤BMI<25, normal weight (%)	3064 (51.1)	1191 (48.5)	1873 (53.0)
25≤BMI<30, overweight (%)	2167 (36.2)	899 (36.6)	1268 (35.9)
BMI>30, obese (%)	734 (12.3)	353 (14.4)	381 (10.8)
Current smoker (%)^d	739 (12.2)	255 (10.3)	484 (13.6)
Short form-12^e
Physical Component Score	56.6 (54.0–57.9)	56.9 (53.8–57.9)	56.6 (54.0–57.9)
Mental Component Score	55.7 (52.3–57.7)	55.7 (52.2–57.7)	55.7 (52.3–57.7)

Notes: Results are reported as medians (interquartile ranges), numbers (percentages). ^an=49 missing values; ^bn=87 missing; ^cn=91 missing; ^dn=46 missing values; ^en=45.

Abbreviation: BMI, body mass index.

Table 4 Characteristics of the DBDSaCS cohort by carrier status and stratified by sex (n=6082)

	Women			Men
	Total	S. aureus-positive	S. aureus-negative	Total	S. aureus-positive	S. aureus-negative
N (%)	2683	924 (34)	1759 (66)	3399	1564 (46)	1835 (54)
Age, years	36.7 (25.7–50.2)	31.3 (24.9–47.6)	38.9 (26.3–51.2)	39.1 (28.5–50.9)	38.8 (28.0–49.8)	39.3 (29.0–51.5)
18–25	580 (22)	234 (40)	346 (60)	417 (12)	208 (50)	209 (50)
26–35	697 (26)	275 (39)	422 (61)	996 (29)	454 (46)	542 (54)
36–45	470 (18)	146 (31)	324 (69)	736 (22)	359 (49)	377 (51)
46–55	515 (19)	155 (30)	360 (70)	674 (20)	305 (45)	369 (55)
56–67	421 (16)	114 (27)	307 (73)	576 (17)	238 (41)	338 (59)
Weight, kg^a	70 (63–80)	70 (64–80)	70 (63–79)	84 (76–93)	85 (77–93)	83 (76–92)
Height, cm^b	170 (165–174)	170 (165–174)	170 (165–174)	183 (178–187)	183 (178–187)	182 (178–187)
BMI, kg/m^2 c	24.3 (22.1–27.5)	24.5 (22.1–27.9)	24.2 (22.0–27.4)	25.2 (23.3–27.4)	25.4 (23.4–27.8)	25.0 (23.1–27.2)
BMI, categorized (kg/m^2)^c
BMI<18.5, underweight (%)	20 (0.8)	7 (0.8)	13 (0.8)	6 (0.2)	5 (0.3)	1 (0.1)
18.5≤BMI<25, normal weight (%)	1464 (55.6)	500 (55.2)	964 (55.9)	1600 (47.6)	691 (44.6)	909 (50.2)
25≤BMI<30, overweight (%)	775 (29.4)	252 (27.8)	523 (30.3)	1392 (41.4)	647 (41.8)	745 (41.2)
BMI>30, obese (%)	373 (14.2)	147 (16.2)	226 (13.1)	361 (10.7)	206 (13.3)	155 (8.6)
Current smoker (%)^d	312 (11.8)	88 (9.6)	224 (12.9)	427 (12.6)	167 (10.7)	260 (14.2)
Short form-12^e
Physical Component Score	56.6 (53.8–57.8)	56.6 (53.8–57.8)	56.6 (53.7–57.9)	56.6 (54.1–57.9)	56.6 (53.9–57.9)	56.6 (54.2–57.9)
Mental Component Score	55.1 (51.2–57.7)	55.0 (50.9–57.7)	55.1 (51.2–57.7)	55.8 (52.8–57.7)	55.8 (52.8–57.7)	55.8 (52.9–57.7)

Notes: Results are reported as medians (interquartile ranges), numbers (percentages). ^an=49 missing values; ^bn=87 missing; ^cn=91 missing; ^dn=46 missing values; ^en=45

Abbreviation: BMI, body mass index.

Table 5 Characteristics of participants sampled from the nose and using the two-step culture method (n=2217)

	Women					Men
	Total	S. aureus-positive	Positive. after 1^st culture	Additional positive after enrichment	S. aureus-negative	Total	S. aureus-positive	Positive. after 1^st culture	Additional positive after enrichment	S. aureus-negative
Number of participants	880	303 (34)	236 (27)	67 (8)	577 (66)	1337	611 (46)	520 (39)	91 (7)	726 (54)
Age<25	169	74 (44)	53 (31)	21 (12)	95 (56)	166	87 (52)	76 (46)	11 (7)	79 (48)
25≤age<35	236	94 (40)	71 (30)	23 (10)	142 (60)	383	172 (45)	141 (37)	31 (8)	211 (55)
35≤age<45	146	52 (36)	43 (29)	9 (6)	94 (64)	297	147 (49)	127 (43)	20 (7)	150 (51)
45≤age<55	179	44 (25)	39 (22)	5 (3)	135 (75)	258	113 (44)	98 (38)	15 (6)	145 (56)
Age≥55	150	39 (26)	30 (20)	9 (6)	111 (74)	233	92 (39)	78 (33)	14 (6)	141 (61)
Age, years	37.7 (26.1–50.9)	30.0 (25.1–46.5)	32.4 (25.3–47.1)	28.0 (24.3–41.8)	41.1 (26.8–52.5)	39.1 (28.7–50.8)	38.3 (28.0–49.4)	38.9 (28.4–49.3)	36.4 (26.7–49.4)	39.9 (29.4–51.8)
Weight, kg^a	69 (62–78)	68 (62–78)	68 (62–78)	66 (59–79)	69 (62–78)	83 (76–92)	84 (76–93)	85 (76–93)	83 (76–90)	83 (76–91)
Height, cm^b	169 (165–173)	169 (165–172)	169 (165–173)	168 (164–171)	169 (165–174)	182 (178–187)	182 (178–187)	182 (178–187)	183 (178–187)	182 (178–187)
BMI, kg/m^2 c	24.0 (21.9–26.7)	23.7 (21.7–26.5)	23.7 (21.7–26.6)	23.7 (21.6–25.5)	24.2 (22.0–26.8)	24.9 (23.1–27.2)	25.1 (23.2–27.8)	25.1 (23.2–28.1)	25.1 (23.1–27.1)	24.8 (23.1–26.9)
Current smoker^d	117 (13.3)	30 (9.9)	24 (10.1)	6 (9.0)	72 (15.1)	178 (13.3)	76 (12.5)	62 (12.0)	14 (15.4)	102 (14.1)

Notes: Numbers with percentages or medians with interquartile ranges. ^an=2 missing values; ^bn=33 missing; ^cn=33 missing; ^dn=2 missing values.

Abbreviation: BMI, body mass index.

Table 6 Prevalence of throat and nasal colonization after primary culture and after enrichment (n=262)

Site of colonization	No.	%	Additional proportion of positive samples after enrichment (%)
S. aureus-positive in nares	106	40
Before enrichment	86	33
After enrichment	20	8	23
S. aureus-positive in throat	117	45
Before enrichment	82	31
After enrichment	35	13	43
S. aureus-positive in nares and/or throat	144	55
Before enrichment	119	45
After enrichment	25	10	21

Note: Numbers and percentages of samples positive for S. aureus among 262 participants with concomitant nasal and throat swabs.

Abbreviation: No., number.

Table 7 Predictors of Staphylococcus aureus colonization by log-binomial regression analysis (n=6082)^a

Characteristics	Women					Men
	Crude model			Adjusted model		Crude model			Adjusted model
	Number	RR	95% CI	RR	95% CI	Number	RR	95% CI	RR	95% CI
Age, 10-year increment	2683	0.88	0.85–0.92	0.87	0.84–0.91	3399	0.97	0.94–0.99	0.96	0.93–0.98
18–25	580	1		1		396	1		1
26–35	697	0.98	0.85–1.12	0.97	0.85–1.11	959	0.91	0.81–1.03	0.90	0.81–0.99
36–45	470	0.77	0.65–0.91	0.75	0.63–0.89	704	0.98	0.87–1.10	0.95	0.84–1.08
46–55	515	0.75	0.63–0.88	0.72	0.61–0.85	653	0.91	0.80–1.03	0.88	0.77–1.00
56-67	421	0.67	0.56–0.81	0.66	0.55–0.79	559	0.83	0.72–0.95	0.80	0.70–0.92
BMI (categorized), kg/m^2 b
Normal weight (18.5≤BMI<25)	1464	1				1600	1
Underweight (BMI<18.5)	20	1.02	0.56–1.87	0.96	0.53–1.74	6	1.93	1.34–2.77	1.80	1.25–2.59
Overweight (25≤BMI<30)	775	0.95	0.84–1.08	1.00	0.88–1.13	1392	1.08	0.99–1.17	1.10	1.01–1.19
Obese (BMI≥30)	373	1.15	1.00–1.33	1.22	1.06–1.41	361	1.32	1.19–1.47	1.36	1.22–1.51
Current smoking^c
Nonsmoker	2341	1		1		2956	1		1
Smoker	312	0.80	0.66–0.96	0.78	0.64–0.93	427	0.83	0.73–0.94	0.83	0.73–0.94

Notes: Results presented as risk ratios (RR) with 95% CI. ^aLog-binomial regression analysis of S. aureus colonization with age (10-year age-groups), body mass index (BMI) categorized cf. WHO definitions, and current smoking as predictors, stratified by sex. Crude model = univariate log-binomial regression without adjustment; adjusted model = based on the crude model with additional adjustment for age, BMI (continuous), and current smoking status. ^bn=91 missing; ^cn=46 missing values.

Abbreviation: BMI, body mass index.