The genus Pasteurella sensu stricto only includes the type species of the genus, Pasteurella multocida, and the species Pasteurella canis, Pasteurella stomatis, Pasteurella dagmatis, and Pasteurella oralis. These species are closely related according to 16S rRNA gene and conserved housekeeping protein sequence phylogeny. Other species are unrelated to P. sensu stricto even though they are validly named Pasteurella. The species excluded from the P. sensu stricto and labeled with the genus name in brackets are only described briefly: [Pasteurella] aerogenes, [Pasteurella] bettyae, [Pasteurella] caballi, [Pasteurella] caecimuris, [Pasteurella] langaaensis, [Pasteurella] mairii, [Pasteurella] skyensis, and [Pasteurella] testudinis. Members of P. sensu stricto are coccobacilli or rods, 0.3–1.0µm in diameter and 1.0–2.0µm in length, they are gram-negative, nonmotile, nonacid fast, and endospores are not formed. Growth is aerobic to microaerophilic or facultatively anaerobic. The metabolism is chemoheterotrophic with both oxidative and fermentative types of metabolism. The electron transport system is cytochrome-based with oxygen, nitrate, or fumarate as the terminal electron acceptor. Nitrate reductase is produced. Members of the genus are normally oxidase-positive, and the alkaline phosphatase and the catalase tests are positive. The optimum growth temperature of members of Pasteurella is 35°C–37°C. Members of the genus produce acid from (+)-d-glucose, (+)-d-galactose, (-)-d-fructose, (+)-d-mannose, and sucrose. There is no acid production from adonitol, meso-inositol, (+)-l-rhamnose, and (-)-l-sorbose. Members of the genus have a DNA GC content (mol%) of 36.8–43.5. In human beings, members of Pasteurella are mainly isolated from wound infections inflicted by animals. In this respect, members of the genus are zoonotic, since the main habitat of the genus Pasteurella is the oral cavity and respiratory tract of vertebrates including both mammals and birds. In animals, typical infections associated with P. multocida are hemorrhagic septicemia in cattle and buffaloes, fowl cholera in poultry, atrophic rhinitis in pigs, and snuffles in rabbits.