Shigella dysenteriae is a species of the rod-shaped bacterial genus Shigella.[1][page needed] Shigella species can cause shigellosis (bacillary dysentery). Shigellae are Gram-negative, nonspore-forming, facultatively anaerobic, nonmotile bacteria.[2]
S. dysenteriae, spread by contaminated water and food, causes the most severe dysentery because of its potent and deadly Shiga toxin, but other species may also be dysentery agents.[3] Contamination is often caused by bacteria on unwashed hands during food preparation, or soiled hands reaching the mouth.[citation needed]