Immunochemical Studies on the Specific Carbohydrate of Group G Streptococci

Abstract

Although Group G streptococci have been recovered frequently from various sources including the human nasopharynx and the serological classification has been firmly established (1), little attention has been directed to the distinctive immunochemical features of the group-specific carbohydrate antigen. In the present study, therefore, the Group G carbohydrate purified from isolated cell walls, has been characterized and a major chemical determinant of antigenic specificity has been identified.In certain respects the chemical content of the cell walls and carbohydrate antigens of Group G streptococci resembles that of Groups A, A-variant, and C streptococci. The trypsinized cell walls of the latter Groups of streptococci contain two major components: a mucopeptide matrix consisting of N-acetylmuramic acid, N-acetylglucosamine, and four amino acids; and the groupspecific carbohydrate, exterior to the mucopeptide, which is composed of rhamnose and N-acetylhexosamine (2, 3). Data to be reported here indicate that the constituent sugars of Group G carbohydrate are rhamnose, galactosamine, and galactose while the composition of the mucopeptide is similar to that of the other three groups of streptococci. Materials and MethodsStreptococcal Strains.--Group G cell walls were prepared from strains D166B, B763A, and B549 obtained from Dr. Rebecca C. Lancefield, The Rockefeller Institute. Preparation of Cell Walls and C-roup-SpeciJ~Carbohydrate.--Cell walls were prepared by previously described methods (4). The group carbohydrate was extracted from the cell walls by the formamide procedure (5).Analytical Methods.--Analyses for rhamnose, muramic acid, glucosamine, galactosamine, and the amino acids were performed by previously described methods (3, 4).

Immunochemical characterization of the carbohydrate antigens of serotype k and Lancefield group G “Streptococcus milleri”

“…• The group G antigen preparation, which still carried over a trace of type k antigen (see Results), contained high amounts of rhamnose (6.45) as well as glucose (1.00), A^-acetylglucosamine (0.24), and A^-acetylgalactosamine (1.15) ( Table 1), and rhamnose inhibited completely the precipitin reaction between the group antigen and its homologous antiserum (Table 2). These results support the previous finding by other investigators that Lancefield group G antigen consists of N-acetylga.lactosamine and rhamnose and its immunodeterminant residue is rhamnose (5). The reason remains unknown at present for the extremely low values of A^-acetyiglucosamine and iV-acetylgalactosamine detected in the crude antigen extracts from the 8 type k and group G strains including K214-2K (Tables 1, 3).…”

“…In conclusion, the type k antigen of S. anginosus is considered to be a unique antigen distinct from any group or type antigen hitherto detected with "S. milleri" strains. The results obtained here for the group G antigen preparation support the chemical structure proposed in the previous report (5).…”

Antigenic Relationships Between Groups B and G Streptococci

“…It is to be noted that the addition of 1 per cent, or 55 micromoles per ml, of L-rhamnose to the Group B antigen-antibody system markedly inhibits the precipit[n reaction, whereas the other constituent sugars of the carbohydrate have no significant inhibitory effect. In this connection it should be emphasized that L-rhamnose also inhibits the Group G precipit[n reaction (5), a finding which suggests, in view of data reported here, that this sugar is a major feature of the antigenic determinants for both Groups B and G carbohydrates.…”

“…Antigenic Relationship between Group B and the Variant Carbohydrates.--It may be recalled that in the Groups A-variant and the C-variant carbohydrates side chains of rhamnose oligosaccharides have been identified as the major determinants of antigenic specificity, whereas in the case of Groups A and C the serologic reactivity of the rhamnose side chains is masked by terminal amino sugars. In a previous paper attention was directed to the fundamental difference between the role of rhamnose in the determinant of the variant carbohydrates on the one hand, and in the determinant of Group G carbohydrate on the other (5). This was suggested by the fact that variant and G carbohydrates do not cross-react with heterologous antisera.…”

Direct detection of groups A, C and G streptococci in clinical specimens by a trivalent colour test

“…It is not possible to extend the present test system to cover group D cultures, since the antigen is not extracted significantly with nitrous acid (34), although groups B and F could be covered. No false positive reactions were obtained with any of the other streptococcal groups tested, even between groups B and G, where some structural similarity in the determinants has been recorded (35).…”