Ibc PROTEINS AS SEROTYPE MARKERS OF GROUP B STREPTOCOCCI

Abstract

A collection of 106 clinical isolates of group B streptococci were type classified by a direct fluorescent antibody test (FAT). In all, 99 of the isolates were typable and belonged to the serotypes Ia (8 strains), Ib (9 strains), Ic (30 strains), II (15 strains), or III (37 strains). The presence of Ibc proteins was demonstrated in 60 of the strains, including 6 of the non-typable isolates. Indirect FAT was performed to test whether the bacteria produced the α and β antigens of the Ibc protein fraction, using specific anti-α and anti-β sera. Both α and β were produced by 22 strains, only α by 33 strains, and only β by 5 strains. The results show that the α and β antigens can be used as markers to detect serovars among group B strains which carry identical serotype-specific carbohydrate antigens, or strains listed as non-typable according to the classification currently used.