Antigenic and genetic homogeneity ofStreptococcus uberisstrains from the bovine udder

Abstract

SUMMARYDNA- fingerprints (Hind III) ofStreptococcus uberisfield isolates from New York State and Europe showed substantial homogeneity, but were different to those of the type strain of the newly proposed psychrophilic speciesS. parauberis. S. uberisstrains had major SDS-heat extracted antigens of molecular masses (Mr) < 14, 40–41, 42–43, 59–61, 80–86 and 118–122 kDa following immunoblotting with rabbit hyperimmune sera. Bovine sera and milk reacted with the 40–41 and 118–122 kDa antigens. Variations in theMrof particular bands were too unevenly distributed to permit formation of subgroups. Although cross reactive, the sizes of the antigens ofS. parauberisstrain NCDO 2020 were substantially different to those ofS. uberis,the most prominent antigen having aMrof 50 kDa. The antigenic and genetic data therefore strongly support the introduction ofS. parauberisas a distinct species.S. uberisstrains reacted with antiserum to Lancefield groups B, E, G and P, their grouping reactions showing no correlation with DNA and immunoblot fingerprints. Lancefield grouping ofS. uberistherefore appears to have little value in identification.