Shigella dysenteriae infection: Shigella dysenteriae is a species of bacteria from the Shigella genus. Dysenteriae is the most common cause of epidemic dysentery in condensed populations such as refugee camps. Infection with this bacteria causes diarrhea.The severity of the disease is variable depending on the underlying health of the individual-the young and old tend to be more severely affected.ysenteriae is the most common cause of epidemic dysentery in condensed populations such as refugee camps. Infection with this bacteria causes diarrhea. The severity of the disease is variable depending on the underlying health of the individual-the young and old tend to be more severely affected.