ROLE OF GROUP-B STREPTOCOCCAL CAPSULAR POLYSACCHARIDES IN THE INDUCTION OF SEPTIC ARTHRITIS

The ability of different serotypes of group B streptococci (GBS) to in duce septic arthritis in mice was compared. Types II, III, IV, V, VI a nd VII GBS were investigated. A highly capsulate strain of type III GB S, COH1, and its mutants, COH1-11 (lacking capsular sialic acid) and C OH1-13 (non-capsulate), obtained by transposon insertional mutagenesis , were used to assess the role of type-specific polysaccharide on the induction of arthritis. At an intravenous dose of 10(7) cfu/mouse, ref erence strains of types II, III, IV: VI and VII and type III strain CO H1 induced arthritis with an incidence ranging from 70 to 90%, For typ e V and strain COH1-II, 10(8) cfu/mouse was required to obtain a 50% i ncidence of arthritis; lesions were not evident with strain COH1-13. T he presence of the capsule played a major role in the induction of GBS septic arthritis. The presence and amount of sialic acid in capsular polysaccharide influenced the incidence of articular lesions. The bact erial dose affected the manifestations of arthritis; the less virulent strains of GBS also induced articular lesions when an adequate number of micro-organisms reached the joints.