Loss of Type Antigen in a Type III Streptococcus and Identification of the Determinant Disaccharide of the Remaining Antigen: A Note on the Nomenclature of Certain Polysaccharides Resembling the Group Antigens of Streptococci

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Abstract
By subcultivating a streptococcal z3 III strain in medium containing anti-Ill serum a strain lacking the type antigen was isolated. Evidence is given that this strain possesses only z3 antigen. From partial acid hydrolysates of formamide extracts of both z3 and a3 III bacteria the same disaccharide was isolated. The most probable structure of the dissacharide is 3-O-[alpha]-N-acetyl-D-glucosaminoyl-N-acetyl-D-galactosamine. It was 250 times more active than [alpha] -methyl-N-acetyl-glucosamine in the inhibition of me z3/anti-z3 system. This denotes that it is an important part of the determinant group of the z3 antigen. By ethanol fractionation of a formamide extract of z3 III bacteria two distinct fractions were isolated. The first fraction reacted only with type-Ill antiserum and consisted of glucose, galactose and rhamnose in the ratio 5:3:1. The second polymer was composed of rhamnose, glucosamine and galactosamine in relative amounts of about 2:1:1. Chemical and serological evidence suggests very strongly that this is the z3 antigen. The similarities between z and true group antigens are discussed.