Enterobacteriaceae

Members of the genus Shigella belong to the family Enterobacteriaceae and are obligate pathogens, causing bacillary dysentery in human and nonhuman primates. The structure of each of the Shigella spp. is typical for the family Enterobacteriaceae . A requisite step in the pathogenesis of shigellosis is invasion of the large intestinal epithelium. Shigellae possess a number of genes whose activation results from specific environmental cues. The classical disease begins as watery diarrhea, then after three to four days the feces becomes scant and contains blood and mucus. The distribution of Shigella is essentially limited to the intestinal tracts of humans and large, captive primates in which shigellosis naturally occurs, and sewage. The disease is transmitted by the fecal-oral route, but the infective dose is so small and the organisms survive long enough that fomites also play a role.