|Straight cells, cocoid to rod-shaped, 0.2-0.4 / 0.4-2.0 µm, Gram-negative, nonmotile. Aerobic, with varying degrees of
microaerophilia, or facultatively anaerobic. Acid is produced through fermentation of D-glucose. Characteristically,
oxidase, catalase, and alkaline phosphatase reactions are positive, but negative reactions can be detected in some
species. Nitrates are reduced to nitrites. For isolation, complex media are required. Obligate parasites in vertebrates. Type
genus: Pasteurella Trevisan 1887. There are eight genera: Actinobacillus, Avibacterium, Aggregatibacter. Gallibacterium,
Haemophilus, Histophilus, Lonepinella, Mannheimia, Pasteurella, Phocoenobacter & Volucribacter.