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Updated: Sep 21, 2026

Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction
Published on: February 24, 2014
Virulence properties of type VII Streptococcus agalactiae (group B streptococci) and immunochemical analysis of
Christina VON Hunolstein1, Laura Parisi1, Luciana Tissi2
1Laboratorio di Batteriologia e Micologia Medica, Rome, Italy.
Abstract:
Strains of a new polysaccharide type of group B streptococci (GBS), type VII, have been isolated from human carriers and invasive infections. Some of these strains bear the protein antigen c or R, as do other GBS serotypes. The capsular type polysaccharide is sialylated and this residue is involved in the immunodeterminant structure. All type VII strains examined were virulent in CD-1 mice; the LD50 after intraperitoneal (i.p.) challenge was 4.57 (SD 0.12) x10(7) cfu for the reference strain and 5.49 (SD 1.5) x10(7) cfu for clinical isolates. A particular feature of this serotype was the ability to induce septic arthritis not only when injected intravenously (i.v.), but also when injected i.p. Rabbit antiserum against the capsular type VII polysaccharide exhibited opsonic activity in a phagocytosis assay and protective activity against infection.
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