Correlation between low levels of maternal IgG antibodies to R protein and neonatal septicemia with group B streptococci carrying R protein.

A method was designed for quantitation of serum antibodies to R protein in group B streptococci (GBS). Four sera from mothers of infants with neonatal septicemia caused by type II, R+ GBS showed a binding range from 400 to 740 cpm in contrast to a range of 690-1,220 cpm in 5 parturients carrying type II, R+ strains in the urogenital tract giving birth to healthy infants (p less than 0.05). The range of antibodies in sera from 8 mothers to infants infected with GBS type III,R+ was 370-750 cpm, whereas the range in sera from 10 carriers of type III,R+ giving birth to healthy infants varied between 510 and 1,280 cpm (p less than 0.01). These findings indicate that R protein is an important virulence factor in neonatal GBS septicemia/meningitis.