The genus Salmonella is divided into 2 species, S. enterica and S. bongori, which include > 2500 known serotypes. Some of these serotypes are named. In such cases, common usage sometimes shortens the scientific name to include only the genus and serotype; for example, S. enterica, subspecies enterica, serotype Typhi is shortened to Salmonella Typhi.
Salmonella may also be divided into 3 groups based on how well the organism is adapted to human hosts:
Those highly adapted to humans and having no nonhuman hosts: This group includes S. Typhi and S. Paratyphi types A, B (also called S. Schottmülleri), and C (also called S. Hirschfeldii), which are pathogenic only in humans and commonly cause enteric (typhoid) fever.
Those adapted to nonhuman hosts or causing disease almost exclusively in animals: Some strains within this group—S. Dublin (cattle), S. Arizonae (reptiles), and S. Choleraesuis (swine)—also cause disease in humans.
Those with a broad host range: This group includes > 2000 serotypes (eg, S. Enteritidis, S. Typhimurium) that cause salmonella gastroenteritis and account for 85% of all Salmonella infections in the US.
