New phenotypic typing scheme for group B streptococci.

AIMS To develop a new typing system for group B streptococci based on 35S-methionine-labelled protein profiles of bacterial proteins. METHODS 377 clinical isolates of group B streptococci were examined by incorporation of 35S-methionine into bacterial proteins under strict anaerobic conditions. After sodium dodecylsulphate-polyacrylamide gel electrophoresis, autoradiography was performed. The patterns produced were visually analysed and categorised into clusters of organisms based on the pattern of band production between 32-46 kilodaltons. RESULTS 294 of the typed strains classified into seven different groups designated a-g. 32 strains failed to incorporate 35S-methionine sufficiently to be grouped and 11 strains did not fall into one of the seven identified groups. Typability, reproducibility, and discrimination of the system was evident. CONCLUSIONS This typing system may help to distinguish between colonising and invasive strains of the organism.