Group B, type III streptococcal cell wall: composition and structural aspects revealed through endo-N-acetylmuramidase-catalyzed hydrolysis

Abstract

Cell walls from a group B, type III streptococcus strain were prepared, purified by extraction with sodium dodecyl sulfate, and solubilized by the M-1 fraction of mutanolysin, an endo-N-acetylmuramidase obtained from Streptomyces globisporus. The lysate was resolved into three fractions by ion-exchange chromatography: a fraction containing peptidoglycan (PG) fragments, free of neutral and acidic sugars and of phosphate; a complex of PG fragments and group B-specific polysaccharide; and a complex of PG fragments and group B-specific polysaccharide and type III-specific polysaccharide. The PG-polysaccharide complexes were large and heterogeneous in molecular size. When subjected to base-catalyzed ,Belimination, both complexes were disintegrated, and polysaccharides and lowmolecular-weight PG fragments could then be separated by gel filtration. The lowmolecular-weight PG fragment-containing fraction contained muramic acid, glucosamine, alanine, lysine, glutamic acid, and serine in molar ratios (to lysine) of 0.92:0.98:3.01:1.00:1.00:0.05. Wall-derived, purified group polysaccharide contained rhamnose, galactose, glucosamine, and phosphorus in molar ratios (to galactose) of 5.03:1.00:1.00:1.05. It also contained an unidentified sugar. Wallderived, purified type III polysaccharide contained galactose, glucosamine, glucose, and N-acetylneuraminic acid in molar ratios (to glucose) of 1.94:0.85:1.00:1.39. On a dry-weight basis, the whole wall lysate contained 19.8 and 20.6% of group and type polysaccharide, respectively. Neither glycerol nor ribitol was found, and all of the cell wall phosphorus was accounted for as polysaccharide, indicating the absence of a wall teichoic acid.

Decreased capacity for type-specific-antigen synthesis accounts for high prevalence of nontypeable strains of group B streptococci in Mexico

“…The type-specific capsular polysaccharide antigen of GBS is secreted as a soluble polysaccharide and is also covalently attached to the insoluble peptidoglycan layer of GBS (2,5,20). It is composed of repeating units of glucose, galactose, Nacetylglucosamine, and N-acetylneuraminic acid (sialic acid) (4,16). Approximately 25% of type-specific polysaccharide consists of sialic acid, which is the main virulence and immunodeterminant portion of the antigen (1,18).…”

“…In contrast to developed countries, where type III is a predominant serotype, the most frequently identified serotypes in Mexico are Ia and Ia/c, with serotype III present at a low frequency. In addition, nontypeable strains that are rarely found in developed countries (Ͻ1%) (1) are reported at a 12% rate in Mexico (4,5). Thus, the low frequency of GBS invasive neonatal infections in Mexico has been attributed to the low prevalence of type III strains along with increased levels of nontypeable GBS (12,13).…”

Deletion of Repeats in the Alpha C Protein Enhances the Pathogenicity of Group B Streptococci in Immune Mice

“…Quantitation of cell-associated CPS and alpha C protein. The amount of capsular polysaccharide (CPS) in mutanolysin cell wall extracts (3,4) was determined by ELISA inhibition (23), with minor modifications (18). In this assay, type Ia CPS-poly-L-lysine (1 g/ml) was applied to the microtiter plate, and rabbit antiserum was raised to the type Ia CPS coupled to tetanus toxoid (1: 100,000 final dilution); purified Ia CPS was used as the standard.…”

Purification of the protein X of Streptococcus agalactiae with a monoclonal antibody

“…Mice were immunized with partially purified protein X, extracted by using mutanolysin (Sigma, St. Louis, MO, U.S.A.) as previously described [11], except that Triton X-100 (0.1%) was added. The extract was passed over an affinity column prepared with the immunoglobulin (Ig) fraction of the absorbed anti-X reference strain rabbit serum, coupled to AH-Sepharose (Pharmacia, Uppsala, Sweden) as described previously [12].…”