Aggregatibacter actinomycetemcomitnas
Aa, as this species is commonly referred to, is a bacteria found in severe infections in the oral cavity, mainly the periodontium. Aggregatibacter actinomycetemcomitnas, which used to be called Actinobacillus actinomycetemcomitans, is a gram negative facultative non motile rod. It is also associated with non oral infections.
Importance
It is one of the major bacteria implicated in destructive periodontal disease. It is specifically associated with Localized Aggressive Periodontitis, LAP[1]. It has also been isolated from actinomycotic lesions (mixed infection with A. israelii). It also possesses virulence factors that enable it to invade tissues, such as leukotoxins formation.
Virulence Factors
- Leukotoxin; kills PMN's and monocytes.
- Immunosupression factors that inhibit blastogenesis, antibody production and activate T-suppressor cells
- inhibition of PMN's functions
- Resistant to complement mediated killing.
Aa Serotypes
- a strain ATCC 29523, frequently in oral cavity, variable Leukotoxin expression.
- b strain Y4, most frequently in LAP, always leukotoxin.
- c strain ATCC 33384, no leukotoxin.
Nomenclature
Newer studies have shown a genetic link between Actinobacillus actinomycetemcomitans , Haemophilus aphrophilus, Haemophilus paraphrophilus and Haemophilus segnis and has suggested the genus Aggregatibacter for them, making Aa called Aggregatibacter actinomycetemcomitnas[2] . This bacteria has been cited in other recent periodontal literature under the new genus name, Aggregatibacter[3][4]