A. actinomycetemcomitans A. arthritidis A. capsulatus A. delphinicola A. equuli A. hominis A. indolicus A. lignieresii A. minor A. muris A. pleuropneumoniae A. porcinus A. rossii A. scotiae A. seminis A. succinogenes A. suis A. ureae Actinobacillus is a genus of Gram-negative, nonmotile and non-spore-forming, oval to rod-shaped bacteria occurring as parasites or pathogens in mammals, birds, and reptiles.

[2] The bacteria are facultatively anaerobic or aerobic, capable of fermenting carbohydrates (without production of gas), and of reducing nitrates.

Actinobacillus (Pasteurella) ureae and A. hominis occur in the respiratory tracts of healthy humans and may be involved in the pathogenesis of sinusitis, bronchopneumonia, and meningitis.

Actinobacilli are susceptible to most antibiotics of the beta-lactam family, aminoglycosides, tetracyclines, chloramphenicol, and many other antibacterial chemotherapeutics.

An analysis of A. actinomycetemcomitans indicated it was monophyletic with Haemophilus aphrophilus and H. segnis, and they were proposed to be reclassified as a new genus, Aggregatibacter (from the Latin aggregare, meaning "to come together").