<unk>  is a genus of rod-shaped (bacillus) Gram-negative bacteria of the family Enterobacteriaceae. The two species of<unk>  are<unk>  enterica and<unk>  bongori. S. enterica is the type species and is further divided into six subspecies that include over 2,600 serotypes.<unk>  was named after Daniel Elmer<unk> on (1850–1914), an American veterinary surgeon.<unk>  species are non-spore-forming, predominantly motile enterobacteria with cell diameters between about 0.7 and 1.5 μm, lengths from 2 to 5 μm, and peritrichous flagella (all around the cell body, allowing them to move). They are chemotrophs, obtaining their energy from oxidation and reduction reactions, using organic sources. They are also facultative anaerobes, capable of generating ATP with oxygen ("aerobically") when it is available, or using other electron acceptors or fermentation ("anaerobically") when oxygen is not available.<unk>  species are intracellular pathogens; of which certain serotypes cause illness. Most infections are due to ingestion of food contaminated by animal feces, or by human feces, such as by a food-service worker at a commercial eatery.<unk>  serotypes can be divided into two main groups—typhoidal and nontyphoidal. Nontyphoidal serotypes are zoonotic and can be transferred from animal-to-human and from human-to-human. They usually invade only the gastrointestinal tract and cause<unk> sis, the symptoms of which can be resolved without antibiotics. However, in sub-Saharan Africa, nontyphoidal<unk>  can be invasive and cause paratyphoid fever, which requires immediate treatment with antibiotics. Typhoidal serotypes can only be transferred from human-to-human, and can cause food-borne infection, typhoid fever, and paratyphoid fever. Typhoid fever is caused by<unk>  invading the bloodstream (the typhoidal form), or in addition spreading throughout the body, invading organs, and secreting endotoxins (the septic form). This can lead to life-threatening hypovolemic shock and septic shock, and requires intensive care including antibiotics.
Salmonella
Shigella
Giardia
Campylobacter jejuni
Vibrio cholerae
Clostridioides difficile 
Enterococcus
Escherichia coli