ANTIBODIES TO GROUP-B STREPTOCOCCI IN NEONATES AND INFANTS

Invasive group B streptococcal (GBS) infections are common in neonates but are rare after the Ist month of life. It is not known why GBS inf ections have this age distribution which differs from that of invasive infections caused by other encapsulated bacteria. The aim of this stu dy was to test the possibility that serum antibodies against the GBS c apsular polysaccharides (CPS) are acquired during the first months of life thereby preventing infections after the neonatal period. Cord ser a were collected from 321 healthy term newborns. A second blood sample was collected at 2, 4, 8, 13 or 26 weeks of age. IgG CPS antibodies ( measured by ELISA) against serotypes Ia, II and III were present in 98 %-100% of all cord sera and decreased continuously during the first 6 months of life. No IgM antibodies against serotype III CPS were presen t in cord sera. Only 16%-17% of the children acquired IgM antibodies a gainst serotype III CPS at 3 and 6 months of age. Conclusion Early acq uisition of IgG or IgM antibodies against CPS of the most common GBS s erotypes was not demonstrated and cannot explain the rare occurrence o f invasive GBS infections in children after the 1st month of life.