A New Serotype-Specific Antigen, Designated Serotype g, from Actinobacillus Actinomycetemcomitans

Abstract

During the isolation of Actinobacillus actinomycetemcomitans from periodontal pockets, a serologically untypeable strain, designated NUM-Aa 4039, was observed. Biochemical and serological identification and PCR-based analysis confirmed that NUM-Aa 4039 was a strain of A. actinomycetemcomitans. An antigen from NUM-Aa 4039 did not react with a to e serotype-specific antibodies in double-immunodiffusion experiments. DNA from the strain could not be amplified by PCR using specific PCR DNA primer of a to f serotype-specific O-polysaccharide gene cluster. The antigen was extracted from whole cells by autoclaving and purified by ion-exchange and gel filtration chromatography. The molecular weight was approximately 180,000. The new antigen was composed of glucose, rhamnose and N-acetyl-glucosamine. Double immunodiffusion and ELISA experiments with antigens and antibodies showed that the antigen had individual antigen determinant. I propose that untyped strain be assigned to a new A. actinomycetemcomitans serotype, designated serotype g.