Group B streptococcal colonization and serotype-specific immunity in pregnant women at delivery.
OBJECTIVE
To describe the relationship between serum concentration of group B streptococcal capsular polysaccharide-specific immunoglobulin (Ig) G, colonization status, race or ethnicity, and age in pregnant women.


METHODS
Pregnant women (n = 3307) were enrolled from geographically and ethnically diverse populations. At the time of admission for delivery, swabs of the lower vagina and rectum were obtained for isolation of group B streptococci. In a subset of women whose sera were available, capsular polysaccharide-specific IgG concentrations were quantified by serotype-specific (Ia, Ib, II, III, and V) enzyme-linked immunosorbent assay and compared by group B streptococcal colonization status.


RESULTS
Group B streptococcal colonization was detected in 856 women (26%), and the rate was significantly higher among black women (37%) than in other racial or ethnic groups (odds ratio 1.7, 95% confidence interval 1.4, 2.1). Colonization status did not differ by study site or age. Colonization with serotypes Ia, II, III, or V was associated with significantly higher serum concentrations of IgG specific for the capsular polysaccharide of the colonizing serotype compared with noncolonization. However, 48% of colonized women had low capsular polysaccharide-specific IgG levels (less than 0.5 microg/mL) in their delivery sera. Colonized teenagers had the lowest median concentration.


CONCLUSIONS
Colonization with group B streptococcus can elicit a systemic immune response, with a cumulative increase in the prevalence of capsular polysaccharide-specific IgG with increasing age. Conversely, low antibody levels in colonized teenagers might account in part for the reported increased risk of group B streptococcal disease in neonates born to these patients.
Campbell
J R
JR
Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA. judithc@bcm.tmc.edu
Hillier
S L
SL
Krohn
M A
MA
Ferrieri
P
P
Zaleznik
D F
DF
Baker
C J
CJ
D000328:Adult; D000907:Antibodies, Bacterial / Q000097:blood; D000918:Antibody Specificity; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005006:Ethnicity; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007743:Labor, Obstetric; D011135:Polysaccharides, Bacterial / Q000276:immunology; D011247:Pregnancy / Q000276:immunology*; D011446:Prospective Studies; D044469:Racial Groups; D012007:Rectum / Q000382:microbiology; D012703:Serotyping; D013292:Streptococcus agalactiae / Q000145:classification / Q000276:immunology* / Q000302:isolation & purification*; D014621:Vagina / Q000382:microbiology
D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D011135:Polysaccharides, Bacterial