Trypsinized cell walls of Group B hemolytic streptococci are composed of a group-specific carbohydrate and mucopeptide. The carbohydrate extracted with hot formamide is composed of rhamnose, N-acetylglucosamine, and galactose. Quantitative precipitin inhibition studies have shown that L rhamose is the significant component of the antigenic determinant. The cross-reactivity between B and G carbohydrates is dependent upon the fact that Lrhamose is a determinant sugar in both antigens.

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).

The antimicrobial and cariostatic activities of the dihydrochloride and dihydrofluoride salts of alexidine (1,6-bis-[2-ethylhexylbiguanido]hexane) were compared to those of chlorhexidine acetate and sodium fluoride in rats implanted orally with Streptococcus mutans 6715 and fed a cariogenic diet. Experimental caries was significantly reduced by the continuous administration of low concentrations of biguanides via the drinking water, but this was accompanied by increased staining of the molars. Very high biguanide concentrations, applied infrequently, directly to the molars, effectively reduced caries and resulted in less staining. A combination of alexidine dihydrochloride and sodium fluoride offered no advantage over either drug alone. Alexidine salts prevented the progressive increase in implanted S. mutans, whereas chlorhexidine acetate practically eliminated the micro-organism from the oral cavity. Sodium fluoride had no effect on the implanted flora. It was concluded that alexidine salts are comparable in cariostatic activity to chlorhexidine. The tooth staining accompanying the use of bisbiguanides can be reduced by adjusting the concentration of the drug and its frequency of application.