Salmonella sp. Coloured transmission electron micrograph (TEM) of a Salmonella sp. bacterium. The cell is rod-shaped with long hair-like flagellae. Salmonella bacteria belong to the Enterobacteriaceae family. They are Gram-negative bacilli bacteria that inhabit the human gut. Salmonella includes the species S. typhi and S. paratyphi, responsible for typhoid and paratyphoid fever in humans. Other serotypes are responsible for gastroenteritis or food poisoning. Around 1800 serotypes of this bacteria have been identified. negatively stained. Magnification unknown.