<unk>  is an oral commensal found also in severe infections in the oral cavity, mainly the periodontium. A.<unk> , previously Actinobacillus<unk> , is a gram negative facultative non motile rod.  It is also associated with non oral infections.
Recent studies have shown a phylogenetic similarity of Actinobacillus<unk>  and  Haemophilus aphrophilus, Haemophilus paraphrophilus, and Haemophilus segnis suggesting the  new genus<unk>  for them. Now or before, the bacterium still holds the longest binomial nomenclature name of a living thing.
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,, 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.
- Leukotoxin; kills PMN's and monocytes.
- Immunosuppression factors that inhibit blastogenesis, antibody production and activate T-suppressor cells
- Inhibition of PMN's functions
- Resistant to complement mediated killing.
- 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
Aggregatibacter actinomycetemcomitans
Haemophilus ducreyi
Mansonella perstans
Porphyromonas gingivalis
Klebsiella rhinoscleromatis
Mycobacterium xenopi
Clostridium botulinum
Gardnerella vaginalis