Salmonella. Coloured transmission electron micrograph (TEM) of Salmonella paratyphi B bacteria (also called Salmonella schotmulleri). These Gram-negative rod-shaped bacteria have flagella (hair-like strands) that are used for movement. This type of Salmonella causes paratyphoid fever, which is a severe type of gastroenteritis (digestive system infection) combined with typhoid-like symptoms (a long, extremely high-temperature fever that may be fatal if left untreated). Infection is usually through ingesting contaminated food or water, but this can be quickly treated by antibiotics. Magnification: x27,200 when printed 10 centimetres wide.