Definition: A genus of gram-negative, oxidase-positive, aerobic, facultatively anaerobic bacteria (family Vibrionaceae) containing rod-shaped to coccoid cells; motile cells ordinarily possess a single, polar flagellum; some species are nonmotile. The metabolism of these organisms is both respiratory and fermentative; nutritional requirements are not stringent. These bacteria are found in water and sewage; some are pathogenic to freshwater and marine animals, and to humans. Effects in humans include cellulitis; wound infections; acute diarrhea (especially caused by Aeromonas sobria); septicemia; urinary tract infection; hepatobiliary, meningeal, and auricular infections; and endocarditis. The type species is Aeromonas hydrophila.