Antigenicity of group B Streptococcus strain "M9" and its prevalence in Japan.
Serological typing of group B streptococci is important for the epidemiological study of group B streptococcal infections. These days, non typable (NT) strains by conventional serotypes were on an increase. In 1984, strain "M9" was isolated from a pregnant woman in Meijo Hospital, Nagoya City; herein the antigenicity and prevalence of strains typed as "M9" were investigated and discussed. The results obtained were as follows: 1) It was confirmed that strain "M9" had a new polysaccharide antigen, different from conventional types, Ia, Ib, II, III, IV and V, type candidate NT6 and type candidate 7271, as found by precipitation and precipitation absorption reaction. This procedure, moreover, was useful for differentiation type candidate NT6 and 7271 from "M9" because of their provisionality. 2) Group B streptococci typed as "M9" were isolated not only from carriers but from patients who were newborn babies and suffered from sepsis. 3) Strain "M9" was not necessarily located in Nagoya City but in Chiba and in Kyoto, this type was isolated from clinical materials already in 1979. 4) It was observed that polysaccharide "M9" liked to combine with protein "R" and without other proteins, as our collection extends.