Color enhanced SEM (scanning electron micrograph) of Shigella sonnei, an aerobic, gram-negative bacteria. Shigella sonnei is a foodborne pathogen that causes the food poisoning "shigellosis." The bacterium is spread by the ingestion of food or water contaminated by infected feces. Symptoms include diarrhea, blood in stool, mucus in stool, pus in stool, and fever. Children and the elderly are more affected by infection. Rehydration and antibiotics are used for treatment. (Image width: 6.25 micrometers)