Age-stratified analysis of serotype-specific baseline immunity against group B streptococcus

Figures & data

Table 1. Comparison of baseline opsonophagocytic activity (OPA) for group B streptococcus (GBS) between risk groups.

Serotypes	Groups*	OPA titers (mean)	95% CI	p-value
Ia	neonates/infants	137	33 – 241	0.596
	pregnant women	285	17 – 552
	old adults	231	3 – 459
III	neonates/infants^a	338	105 – 570	0.002
	pregnant women^b	1377	941 – 1813
	old adults^b	1350	700 – 2000
V	neonates/infants^a	161	−5 – 327	<0.001
	pregnant women^b	9414	6825 – 12003
	old adults^c	3669	1579 – 5759

* The same letters (alphabetical superscripts) indicate non-significant difference between groups based on Tukey’s multiple comparison test.

Table 2. Comparison of baseline opsonophagocytic activity (OPA) for group B streptococcus (GBS) between risk groups: proportion in each range stratified by the magnitude of OPA titer.

Serotype	OPA titer	Case No. (%)			p-value
		neonates/infants	pregnant women	old adults
Ia	<100	21 (70)	24 (80)	25 (83.3)	0.156
	100–499	6 (20)	2 (6.7)	2 (6.7)
	500–999	2 (6.7)	0 (0)	0 (0)
	>1,000	1 (3.3)	4 (13.3)	3 (10)
III	<100	18 (60)	4 (13.3)	4 (13.3)	<0.001
	100–499	4 (13.3)	4 (13.3)	6 (20)
	500–999	6 (20)	6 (20)	7 (23.3)
	>1,000	2 (6.7)	16 (53.3)	13 (43.3)
V	<100	23 (76.7)	0 (0)	2 (6.7)	<0.001
	100–499	5 (16.7)	0 (0)	2 (6.7)
	500–999	1 (3.3)	2 (6.7)	5 (16.7)
	>1,000	1 (3.3)	28 (93.3)	21 (70)

Figure 1. Comparison of baseline opsonophagocytic activity (OPA) titers for group B streptococcus (GBS) between three age groups (upper panel, mean ± standard deviation; lower panel, point distribution): (a) serotype Ia, (b) serotype III, and (c) serotype V. NOTE: the same letters (alphabetical superscripts) indicate non-significant differences between groups based on Tukey’s multiple comparison tests.

Table 3. Comparison of baseline opsonophagocytic activity (OPA) titers between group B streptococcus (GBS)-colonized and non-colonized pregnant women: proportion in each range stratified by the magnitude of OPA titer.

Serotype	OPA titer	Case No. (%)		p-value
		GBS colonized (N = 4)	GBS non-colonized (N = 26)
Ia	<100	2 (50)	22 (84.6)	0.065
	100–499	0 (0)	2 (7.7)
	500–999	0 (0)	0 (0)
	>1,000	2 (50)	2 (7.7)
III	<100	0 (0)	4 (15.4)	0.764
	100–499	1 (25)	3 (11.5)
	500–999	1 (25)	5 (19.2)
	>1,000	2 (50)	14 (53.9)
V	<100	0 (0)	0 (0)	0.566
	100–499	0 (0)	0 (0)
	500–999	0 (0)	2 (7.7)
	>1,000	4 (100)	24 (92.3)

Table 4. Group B streptococcus (GBS) serotypes and opsonophagocytic activity (OPA) titers among four GBS-colonized pregnant women.

No.	Age	Serotypes	OPA titer
			Serotype Ia	Serotype III	Serotype Ⅴ
1	30	NT	2	11	2,773
2	34	Ⅰa	2,001	3,218	3,020
3	29	III, Ⅷ	2,916	2,876	17,496
4	27	Ⅰb	2	614	1,984

Figure 2. Comparison of baseline opsonophagocytic activity (OPA) titers for group B streptococcus (GBS) between GBS-colonized and GBS non-colonized pregnant women at their 35–37 weeks prenatal screening: distribution of OPA titers in each group (red circles, GBS-colonized women and blue circles, GBS non-colonized women).

Table 5. Comparison of baseline opsonophagocytic activity (OPA) titers between preterm and full-term neonates/infants.

	Groups	Preterm (N = 16)	Full-term (N = 14)	p-value
Gestational age at birth, mean weeks (95% CI)		35.0 (33.6–36.4)	39.6 (39.0–40.3)	<0.001
Birth weight, mean Kg (95% CI)		2.2 (1.9–2.4)	3.2 (3.0–3.4)	<0.001
Twin pregnancy		2 (12.5%)	0 (0%)	0.171
Maternal GBS colonization		2/14 (14.3%)	1/10 (10%)	0.754
OPA titers, mean (95% CI)	Serotype Ia	207 (12–402)	57 (15–99)	0.127
	Serotype III	355 (35–674)	319 (−68 – 705)	0.878
	Serotype V	244 (−75 – 564)	65 (9–120)	0.278

GBS, group B streptococcus