Salmonella. Coloured transmission electron micrograph of a Salmonella enteritidis bacterium. This Gram-negative rod-shaped bacillus is a cause of food poisoning (Salmonellosis) in humans. Note the presence of many flagellae used for motility. Salmonella enteritidis produces enterotoxins which act on the small intestine. Infection occurs when numbers of these bacteria are ingested through the medium of contaminated food, particularly meat, milk and chicken eggs. Typical Salmonella food poisoning occurs with symptoms including vomiting, nausea, abdominal pain and diarrhoea. The infection is usually controllable and rarely fatal. Magnification: x13,100 6x4.5cm size.