Merck Manual

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Overview of Salmonella Infections


Larry M. Bush

, MD, FACP, Charles E. Schmidt College of Medicine, Florida Atlantic University;

Maria T. Vazquez-Pertejo

, MD, FACP, Wellington Regional Medical Center

Last full review/revision Feb 2020| Content last modified Feb 2020
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The genus Salmonella is divided into 2 species, S. enterica and S. bongori, which include > 2400 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.

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