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Aggregatibacter actinomycetemcomitans: Wikis


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Aggregatibacter actinomycetemcomitans
Scientific classification
Kingdom: Bacteria
Phylum: Proteobacteria
Class: Gammaproteobacteria
Order: Pasteurellales
Family: Pasteurellaceae
Genus: Aggregatibacter
Species: actinomycetemcomitans

Aggregatibacter actinomycetemcomitans is an oral commensal found also in severe infections in the oral cavity, mainly the periodontium. A. actinomycetemcomitans, previously Actinobacillus actinomycetemcomitans, is a gram negative facultative non motile rod. It is also associated with non oral infections. It was first discovered by periodontist Dr. Jorgen Slots, now a University of Southern California faculty member.

Bacterium actinomycetem comitans’ was described by Klinger (1912) as coccobacillary bacteria isolated together with Actinomyces from actinomycotic lesions of man. It was reclassified as Actinobacillus actinomycetemcomitans by Topley & Wilson (1929) and as Haemophilus actinomycetemcomitans by Potts et al. (1985). The species has attracted attention because of its association with localized aggressive periodontitis (Slots & Ting, 1999; Haubek et al., 2001). [1]



Recent studies have shown a phylogenetic similarity of Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus, Haemophilus paraphrophilus, and Haemophilus segnis suggesting the new genus Aggregatibacter for them.[1]


It is one of the bacteria which might be implicated in destructive periodontal disease. Although it has been found more frequently in localized aggressive periodontitis,[2] prevalence in any population is rather high. It has also been isolated from actinomycotic lesions (mixed infection with certain Actinomyces species, in particular Actinomyces israelii). It possesses certain virulence factors that enable it to invade tissues, such as leukotoxin.

Virulence Factors

- Leukotoxin; kills PMN's and monocytes.

- Cytolethal distending toxin

- Immunosuppression factors that inhibit blastogenesis, antibody production and activate T-suppressor cells

- Inhibition of PMN's functions

- Resistant to complement mediated killing.

A. actinomycetemcomitans Serotypes

- a strain, for example ATCC 29523, frequently in oral cavity, variable leukotoxin expression.

- b strain Y4, most frequently in localized aggressive periodontitis, leukotoxin expression.

- c strain ATCC 33384, low leukotoxin.

- serotypes d, e




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