<P> Salmonella is a genus of rod - shaped (bacillus) gram - negative bacteria of the Enterobacteriaceae family . The two species of Salmonella are Salmonella enterica and Salmonella bongori . Salmonella enterica is the type species and is further divided into six subspecies that include over 2,500 serotypes . </P> <P> Salmonella 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). 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 when oxygen is not available, using other electron acceptors or fermentation ("anaerobically"). S. enterica subspecies are found worldwide in all warm - blooded animals and in the environment . S. bongori is restricted to cold - blooded animals, particularly reptiles . </P> <P> Salmonella species are intracellular pathogens: certain serotypes cause illness . Nontyphoidal serotypes can be transferred from animal - to - human and from human - to - human . They usually invade only the gastrointestinal tract and cause Salmonella food poisoning; symptoms resolve without antibiotics . However, in sub-Saharan Africa they 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 Salmonella food poisoning, typhoid fever and paratyphoid fever . Typhoid fever occurs when Salmonella invades the bloodstream--the typhoidal form; or in addition spreads throughout the body, invades organs, and secretes endotoxins--the septic form . This can lead to life - threatening hypovolemic shock and septic shock and requires intensive care including antibiotics . </P> <P> The genus Salmonella is part of the family of Enterobacteriaceae . Its taxonomy has been revised and has the potential to confuse . The genus comprises two species, Salmonella bongori and Salmonella enterica, the latter of which is divided into six subspecies: S. e. enterica, S. e. salamae, S. e. arizonae, S. e. diarizonae, S. e. houtenae, and S. e. indica . The taxonomic group contains more than 2500 serotypes (also serovars) defined on the basis of the somatic O (lipopolysaccharide) and flagellar H antigens (the Kauffman--White classification). The full name of a serotype is given as, for example, Salmonella enterica subsp . enterica serotype Typhimurium, but can be abbreviated to Salmonella Typhimurium . Further differentiation of strains to assist clinical and epidemiological investigation may be achieved by antibiotic sensitivity testing and by other molecular biology techniques such as pulsed - field gel electrophoresis, multilocus sequence typing, and, increasingly, whole genome sequencing . Historically, salmonellae have been clinically categorized as invasive (typhoidal) or noninvasive (nontyphoidal salmonellae) based on host preference and disease manifestations in humans . </P>

Salmonella spp. typically transmitted from animals to humans