Naturally occurring IgG antibody levels to the Staphylococcus aureus protein IsdB in humans

Figures & data

Table 1. Demographic characteristics of the study populations.

Group	Race White (%)	Gender Female (%)	Age (years) Median (range)
Healthy (n = 21)	86	57	40 (28–56)
Hospital controls (n = 50)	92	50	77 (19–94)
Hospital S. aureus cases (n = 52)	88	27	66 (21–91)

Table 2. Clinical characteristics of hospitalized patients with S. aureus or other infections

	Hospital S. aureus cases n = 52	Hospital controls ^a n = 50
Coexisting medical conditions	n (%)	n (%)
Malignancy	5 (10)	6 (12)
Hydrocephalus	2 (4)	3 (6)
Bone conditions^b	23 (44)	12 (24)
Spinal disorder	7 (13)	2 (4)
Sepsis/UTI	3 (6)	11 (22)
Pneumonia	4 (8)	4 (8)
Gastrointestinal	2 (4)	10 (20)
Other^c	6 (11)	2 (4)
Immunosuppression or other risk factors
Active malignancy	2 (4)	7 (14)
Diabetes	2 (4)	2 (4)
Elderly	5 (10)	7 (14)
Steroids	3 (6)	1 (2)
Hemodialysis	2 (4)	1 (2)
Cirrhosis	1 (2)	0 (0)
Other^d	1 (2)	1 (2)
None	36 (69)	31 (62)

^aPathogens isolated from hospital controls: Escherichia coli (25), Pseudomonas aeruginosa (8), Staphylococcus epidermidis (4), Enterococcus species (2), Proteus mirabilis (2), Streptococcus pneumoniae (2), Acinetobacter baumannii (1), Candida albicans (1), Enterobacter species (1), Group G Streptococcus (1), Hemophilus influenzae (1), Klebsiella oxytoca (1), Klebsiella pneumoniae (1). ^b Bone conditions included osteoarthritis, septic arthritis, bone trauma, hip or knee joint replacements, bone necrosis. ^c Other Underlying Medical Condition: Cellulitis, Fasciitis, Whipple's Operation, PUO, aortic aneurysm, craniopharyngioma. ^d Other Immunosuppression or Risk Factor: Organ failure, previous endocarditis.

Table 3. IsdB-specific IgG Levels at study entry.

Group	Geometric mean concentration^a (µg /mL)	95% CI	Range
Healthy (n = 21)	34.9	24.2–50.2	5.0–133.7
Hospital controls (n = 50)	19.6	14.1–27.3	0.8–162.4
Hospital S. aureus cases (n = 52)	37.2	28.3–48.9	4.0–500.8

^aGeometric mean of IsdB-specific IgG levels at study entry. IsdB: iron-surface determinant B.

Figure 1. Longitudinal scatterplot of anti-IsdB antibody levels (ug/mL) over time in the Healthy Group.

Figure 2. Longitudinal scatterplot of Anti-IsdB antibody levels (ug/mL) over time in the hospital controls and hospital cases.

Table 4. Geometric mean fold rise in IsdB-specific IgG levels among the hospital cases and controls*.

Type of infection	Group	Time Point of Maximum antibody titer (days)	N	Geometric mean fold-rise	95% CI	Range
All	Hospital S. aureus cases	≥ 7	36	2.0	1.4–2.8	0.4–47.7
		≥ 10	31	2.1	1.4–3.1	0.4–47.7
		≥ 14	28	2.0	1.3–3.0	0.4–47.7
	Hospital controls	≥ 7	25	1.1	0.9–1.2	0.7–2.8
		≥ 10	20	1.0	0.9–1.2	0.7–2.8
		≥ 14	17	0.7	0.3–1.6	0.0–2.8
Blood stream infections	Hospital S. aureus cases	≥ 7	18	2.5	1.4–4.4	1.0–47.7
		≥ 10	15	2.8	1.5–5.4	1.1–47.7
		≥ 14	12	2.7	1.3–5.6	1.1–47.7
	Hospital controls	≥ 7	15	1.1	0.9–1.4	0.7–2.8
		≥ 10	13	1.1	0.9–1.3	0.7–2.8
		≥ 14	10	0.6	0.1–2.5	0.0–2.8

Note: *Only includes patients with serum collected on days < 7, and ≥ 7, ≥ 10 or ≥ 14. IsdB, iron-surface determinant B.

Figure 3. Reverse Cumulative Distribution Analysis of IsdB-specific IgG Titers (µg /mL) in the hospital cases and controls.