Structural and genetic analyses of O polysaccharide from Actinobacillus actinomycetemcomitans serotype f.
The oral bacterium Actinobacillus actinomycetemcomitans is implicated as a causative agent of localized juvenile periodontitis (LJP). A. actinomycetemcomitans is classified into five serotypes (a to e) corresponding to five structurally and antigenically distinct O polysaccharide (O-PS) components of their respective lipopolysaccharide molecules. Serotype b has been reported to be the dominant serotype isolated from LJP patients. We determined the lipopolysaccharide O-PS structure from A. actinomycetemcomitans CU1000, a strain isolated from a 13-year-old African-American female with LJP which had previously been classified as serotype b. The O-PS of strain CU1000 consisted of a trisaccharide repeating unit composed of L-rhamnose and 2-acetamido-2-deoxy-D-galactose (molar ratio, 2:1) with the structure -->2)-alpha-L-Rhap-(1-3)-2-O-(beta-D-GalpNAc)-alpha-L-Rhap-(1-->* O-PS from strain CU1000 was structurally and antigenically distinct from the O-PS molecules of the five known A. actinomycetemcomitans serotypes. Strain CU1000 was mutagenized with transposon IS903phikan, and three mutants that were deficient in O-PS synthesis were isolated. All three transposon insertions mapped to a single 1-kb region on the chromosome. The DNA sequence of a 13.1-kb region surrounding these transposon insertions contained a cluster of 14 open reading frames that was homologous to gene clusters responsible for the synthesis of A. actinomycetemcomitans serotype b, c, and e O-PS antigens. The CU1000 gene cluster contained two genes that were not present in serotype-specific O-PS antigen clusters of the other five known A. actinomycetemcomitans serotypes. These data indicate that strain CU1000 should be assigned to a new A. actinomycetemcomitans serotype, designated serotype f. A PCR assay using serotype-specific PCR primers showed that 3 out of 20 LJP patients surveyed (15%) harbored A. actinomycetemcomitans strains carrying the serotype f gene cluster. The finding of an A. actinomycetemcomitans serotype showing serological cross-reactivity with anti-serotype b-specific antiserum suggests that a reevaluation of strains previously classified as serotype b may be warranted.
Kaplan
J B
JB
Department of Oral Pathology, Biology and Diagnostic Sciences, New Jersey Dental School, Newark, New Jersey 07103-2714, USA. kaplanjb@umdnj.edu
Perry
M B
MB
MacLean
L L
LL
Furgang
D
D
Wilson
M E
ME
Fine
D H
DH
D000189:Actinobacillus Infections / Q000382:microbiology; D000293:Adolescent; D016976:Aggregatibacter actinomycetemcomitans / Q000737:chemistry / Q000145:classification* / Q000235:genetics / Q000276:immunology*; D000907:Antibodies, Bacterial / Q000276:immunology; D002240:Carbohydrate Sequence; D005260:Female; D006801:Humans; D008969:Molecular Sequence Data; D019081:O Antigens / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology; D010518:Periodontitis / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D012703:Serotyping
D000907:Antibodies, Bacterial; D019081:O Antigens