Negatively stained Shigella dysenteriae prepared from a stool sample (bacillary dysentery). Shigella are a genus of non-lactose-fermenting, nonmotile, gram-negative rods belonging to the family Enterobacteriaceae. The species S. dysenteriae, also known as Shiga's bacillus is a virulent form isolated during a severe epidemic of dysentery in Japan in 1896. S. flexneri is a frequent cause of acute diarrhea in man, and is synonymous with group B dysentery bacilli. TEM Magnification =x11,000 at 2.25 fill size.