title: Leukotoxic activity of Aggregatibacter actinomycetemcomitans and periodontal attachment loss.
abstract: Aggregatibacter actinomycetemcomitans is a Gram-negative periodontitis-associated bacterium that expresses a toxin that selectively affects leukocytes. This leukotoxin is encoded by an operon belonging to the core genome of this bacterial species. Variations in the expression of the leukotoxin have been reported, and a well-characterized specific clonal type (JP2) of this bacterium with enhanced leukotoxin expression has been isolated. In particular, the presence of the JP2 genotype significantly increases the risk for the progression of periodontal attachment loss (AL). Based on these findings we hypothesized that variations in the leukotoxicity are linked to disease progression in infected individuals. In the present study, the leukotoxicity of 239 clinical isolates of A. actinomycetemcomitans was analysed with different bioassays, and the genetic peculiarities of the isolates were related to their leukotoxicity based on examination with molecular techniques. The periodontal status of the individuals sampled for the presence of A. actinomycetemcomitans was examined longitudinally, and the importance of the observed variations in leukotoxicity was evaluated in relation to disease progression. Our data show that high leukotoxicity correlates with an enhanced risk for the progression of AL. The JP2 genotype isolates were all highly leukotoxic, while the isolates with an intact leukotoxin promoter (non-JP2 genotypes) showed substantial variation in leukotoxicity. Genetic characterization of the non-JP2 genotype isolates indicated the presence of highly leukotoxic genotypes of serotype b with similarities to the JP2 genotype. Based on these results, we conclude that A. actinomycetemcomitans harbours other highly virulent genotypes besides the previously described JP2 genotype. In addition, the results from the present study further highlight the importance of the leukotoxin as a key virulence factor in aggressive forms of periodontitis.
authors.affiliation: Division of Molecular Periodontology, Department of Odontology, Faculty of Medicine, Umeå University, Umeå, Sweden.
authors.forename: Carola
authors.initials: C
authors.lastname: Höglund Åberg
authors.affiliation: Section for Pediatric Dentistry, Department of Dentistry, Health, Aarhus University, Aarhus, Denmark.
authors.forename: Dorte
authors.initials: D
authors.lastname: Haubek
authors.affiliation: Dental School University of Ghana, Accra, Ghana.
authors.forename: Francis
authors.initials: F
authors.lastname: Kwamin
authors.affiliation: Division of Molecular Periodontology, Department of Odontology, Faculty of Medicine, Umeå University, Umeå, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Johansson
authors.affiliation: Oral Microbiology, Department of Odontology, Faculty of Medicine, Umeå University, Umeå, Sweden.
authors.forename: Rolf
authors.initials: R
authors.lastname: Claesson
mesh_terms: D000293:Adolescent; D016976:Aggregatibacter actinomycetemcomitans / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D004269:DNA, Bacterial / Q000235:genetics; D018450:Disease Progression; D005098:Exotoxins / Q000235:genetics* / Q000633:toxicity*; D015964:Gene Expression Regulation, Bacterial; D005838:Genotype; D005869:Ghana / Q000453:epidemiology; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D016871:Pasteurellaceae Infections / Q000453:epidemiology; D017622:Periodontal Attachment Loss / Q000453:epidemiology / Q000382:microbiology*; D011401:Promoter Regions, Genetic; D012307:Risk Factors; D037521:Virulence Factors / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D005098:Exotoxins; D037521:Virulence Factors; C018579:leukotoxin
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