Lack of serotype antigen in A. actinomycetemcomitans.
Aggregatibacter actinomycetemcomitans is divided into 6 serotypes. Occurrence of non-serotypeable strains is known, but background reasons are unclear. We hypothesized that non-serotypeable strains represent new serotypes or have altered expression of serotype-specific polysaccharide antigen (S-PA). We first characterized 311 strains from 189 individuals using both immunoassay- and PCR-based serotyping. Next, using natural human infection and rabbit immunization approaches, we clarified whether the phenotypically non-serotypeable strains expressed S-PA. Immunoassay identified serotypes a-f among 216 strains from 159 individuals. The remaining 95 strains from 30 individuals were phenotypically non-serotypeable. Yet, all these strains were identified by PCR-typing as serotype a-, b-, c-, or f. Non-serotypeability was confirmed by Western immunoblot with respective rabbit antisera. Patient sera remained non-reactive with autologous non-serotypeable strains at the serotype-specific region. Rabbit immunization with a phenotypically non-serotypeable strain induced no antibody production against S-PA. Thus, phenotypically non-serotypeable strains did not include novel serotypes, but lacked S-PA expression.
Section of Oral Microbiology, Institute of Odontology, Umeå University, Umeå SE-90187, Sweden.
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E
Kanasi
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B
Doğan
M
M
Karched
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Thay
J
J
Oscarsson
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S
Asikainen
D016976:Aggregatibacter actinomycetemcomitans / Q000145:classification* / Q000378:metabolism; D000942:Antigens, Bacterial / Q000032:analysis / Q000145:classification / Q000378:metabolism*; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D006801:Humans; D008070:Lipopolysaccharides / Q000145:classification* / Q000378:metabolism; D019081:O Antigens / Q000145:classification / Q000378:metabolism; D010518:Periodontitis / Q000382:microbiology*; D011135:Polysaccharides, Bacterial / Q000032:analysis / Q000145:classification / Q000378:metabolism*; D012703:Serotyping / Q000379:methods*; D013045:Species Specificity
D000942:Antigens, Bacterial; D008070:Lipopolysaccharides; D019081:O Antigens; D011135:Polysaccharides, Bacterial