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.