title: Inhibition of Actinobacillus actinomycetemcomitans leukotoxicity by bacteria from the subgingival flora.
abstract: Actinobacillus actinomycetemcomitans produces a pore-forming leukotoxin that lyses human polymorphonuclear leukocytes and monocytes. Certain proteolytic bacteria may coexist with A. actinomycetemcomitans in periodontal pockets. We aimed therefore to examine whether oral bacteria can modify the leukotoxicity of A. actinomycetemcomitans. A total of 55 strains representing 45 bacterial species of the subgingival flora were tested. Each strain was incubated with the highly toxic strain of A. actinomycetemcomitans HK 1519 and the leukotoxic activity of the suspension against human polymorphonuclear leukocytes was determined from the activity of the lactate dehydrogenase released upon lysis of the leukocytes. Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Prevotella melaninogenica and Prevotella loeschii inhibited the leukotoxicity of A. actinomycetemcomitans cells as well as the activity of leukotoxin purified from the same strain. The bacterial strains without the ability to block leukotoxic activity also failed to destroy pure leukotoxin even after 5 h of incubation. The proteolytic degradation of leukotoxin by P. gingivalis was mainly dependent on the activity of the enzymes R- and K-gingipains. P. intermedia and P. nigrescens also degraded the leukotoxin by enzymes. The results imply a role of the periodontal microflora in modifying the virulence of A. actinomycetemcomitans by destroying its leukotoxin.
authors.affiliation: Department of Odontology, Divisions of Oral Microbiology and Periodontology, Faculty of Medicine and Odontology, Umeå University, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Johansson
authors.forename: L
authors.initials: L
authors.lastname: Hänström
authors.forename: S
authors.initials: S
authors.lastname: Kalfas
mesh_terms: D018829:Adhesins, Bacterial; D016976:Aggregatibacter actinomycetemcomitans / Q000472:pathogenicity* / Q000502:physiology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D003546:Cysteine Endopeptidases / Q000378:metabolism; D003773:Dental Plaque / Q000382:microbiology*; D017753:Ecosystem; D004591:Electrophoresis, Polyacrylamide Gel; D005098:Exotoxins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000080867:Gingipain Cysteine Endopeptidases; D006388:Hemagglutinins / Q000378:metabolism; D006801:Humans; D009504:Neutrophils / Q000187:drug effects*; D016966:Porphyromonas gingivalis / Q000201:enzymology / Q000502:physiology; D018720:Prevotella / Q000201:enzymology / Q000502:physiology; D014774:Virulence / Q000187:drug effects
chemical_list: D018829:Adhesins, Bacterial; D017077:Culture Media, Conditioned; D005098:Exotoxins; D000080867:Gingipain Cysteine Endopeptidases; D006388:Hemagglutinins; C018579:leukotoxin; D003546:Cysteine Endopeptidases