Pasteurella is a genus of Gram-negative, facultatively anaerobic bacteria. Pasteurella species are nonmotile and pleomorphic, and often exhibit bipolar staining ("safety pin" appearance). Most species are catalase- and oxidase-positive. The genus is named after the French chemist and microbiologist, Louis Pasteur, who first identified the bacteria now known as Pasteurella multocida as the agent of chicken cholera.