Salmonella species (spp.) are a group of bacteria capable of causing disease which live naturally in the intestinal tracts of humans and other warm-blooded animals, especially birds. They are the second most common cause of bacterial foodborne illness in Ireland (Campylobacter spp. is the most frequent cause). They are facultative anaerobic Gram-negative rods and members of the Enterobacteriaceae group.
The genus Salmonella contains two species: Salmonella enterica and Salmonella bongori. Salmonella enterica is an important agent of foodborne illness and is sub-classified into six subspecies, of which S. enterica subspecies enterica is the most important for human health.
The genus S. enterica can be subdivided into more than 2,500 serotypes. S. Typhimurium and S. Enteritidis are the most frequently isolated serotypes in human clinical cases in Ireland. Serotypes are further subdivided by resistance to bacteriophages (phage types or lystotypes), antibiotics or heavy metals; biochemical characteristics (biovars or biotypes); or sensitivity to or production of bacteriocins.