Distribution of serovariants of group B streptococci in isolates from England and Norway.

The distribution of capsular polysaccharide antigen (CHO) types, surface-exposed c proteins alpha (c alpha) and beta (c beta) and an R-protein antigen was examined in 334 group B streptococci (GBS) isolates from three groups of patients hospitalised in England and Wales or Norway. The isolates were from 108 carriers, 67 cases of neonatal infection and 154 cases of adult infection. Each group contained all CHO types (Ia, Ib, II, III, IV, V and NT); type III strains predominated except in the adult infected group. Strains within each CHO type could be further subdivided by the protein markers into five subtypes by a combined typing system. The proportion of type Ib and type III strains in the neonatal infection cases and of type Ib strains in the adult infection cases significantly outnumbered isolates of these serotypes among the carrier strains. Twenty-nine different serovariants were identified; 24, 13 and 23 serovariants among the carrier, neonatal infection and adult infection isolates, respectively. Certain CHO antigen-protein associations were identified, notably those between Ia/c alpha, Ib/c alpha beta and III/R. The proportion of invasive isolates that expressed protein was not higher than in the carrier isolates. All CHO-type Ib isolates contained a c protein, but 7% of the Ib isolates did not contain any of these proteins. These findings indicate that this combined typing approach may be useful in examining epidemiological problems associated with GBS.