However, in sub-Saharan Africa, nontyphoidal Salmonella can be invasive and cause paratyphoid fever, which requires immediate antibiotic treatment.

At the time, Smith was working as a research laboratory assistant in the Veterinary Division of the United States Department of Agriculture.

[13] Initially, Salmonella Choleraesuis was thought to be the causative agent of hog cholera, so Salmon and Smith named it "Hog-cholera bacillus".

A 2014 study showed that S. Reading is very common among young turkey samples, but it is not a significant contributor to human salmonellosis.

[19][20] Most subspecies of Salmonella produce hydrogen sulfide,[21] which can readily be detected by growing them on media containing ferrous sulfate, such as is used in the triple sugar iron test.

[14][16][17][18] Salmonella species lead predominantly host-associated lifestyles, but the bacteria were found to be able to persist in a bathroom setting for weeks following contamination, and are frequently isolated from water sources, which act as bacterial reservoirs and may help to facilitate transmission between hosts.

Serotypes are usually put into subspecies groups after the genus and species, with the serotypes/serovars capitalized, but not italicized: An example is Salmonella enterica serovar Typhimurium.

SPIs are regulated by complex and fine-tuned regulatory networks that allow the gene expression only in the presence of the right environmental stresses.

[58] Molecular modeling and active site analysis of SdiA homolog, a putative quorum sensor for Salmonella typhimurium pathogenicity, reveals the specific binding patterns of AHL transcriptional regulators.

Endotoxins first act on the vascular and nervous apparatus, resulting in increased permeability and decreased tone of the vessels, upset of thermal regulation, and vomiting and diarrhoea.

In severe forms of the disease, enough liquid and electrolytes are lost to upset the water-salt metabolism, decrease the circulating blood volume and arterial pressure, and cause hypovolemic shock.

Infants and young children are much more susceptible to infection, easily achieved by ingesting a small number[clarification needed] of bacteria.

[citation needed] The organisms enter through the digestive tract and must be ingested in large numbers to cause disease in healthy adults.

[citation needed] About 2,000 serotypes of nontyphoidal Salmonella are known, which may be responsible for as many as 1.4 million illnesses in the United States each year.

This second wave of iNTS possibly originated in the Congo Basin, and early in the event picked up a gene that made it resistant to the antibiotic chloramphenicol.

This created the need to use expensive antimicrobial drugs in areas of Africa that were very poor, making treatment difficult.

[67] Successful forms of prevention come from existing entities such as the FDA, United States Department of Agriculture, and the Food Safety and Inspection Service.

All of these organizations create standards and inspections to ensure public safety in the U.S. For example, the FSIS agency working with the USDA has a Salmonella Action Plan in place.

[69] In Latin America an orally administered vaccine for Salmonella in poultry developed by Dr. Sherry Layton has been introduced which prevents the bacteria from contaminating the birds.

[citation needed] While travelling to their target tissue in the gastrointestinal tract, Salmonella is exposed to stomach acid, to the detergent-like activity of bile in the intestine, to decreasing oxygen supply, to the competing normal gut flora, and finally to antimicrobial peptides present on the surface of the cells lining the intestinal wall.

[77] The switch to virulence gives access to a replication niche inside the host (such as humans), and can be summarised into several stages:[citation needed] Nontyphoidal serotypes preferentially enter M cells on the intestinal wall by bacterial-mediated endocytosis, a process associated with intestinal inflammation and diarrhoea.

The combination of the inflammation caused by bacterial-mediated endocytosis and the disruption of tight junctions is thought to contribute significantly to the induction of diarrhoea.

The secretion of T3SS-2 effectors by Salmonella is required for its efficient survival in the host cytosol and establishment of systemic disease.

[81] A 2018 Imperial College London study also shows how salmonella disrupt specific arms of the immune system (e.g. 3 of 5 NF-kappaB proteins) using a family of zinc metalloproteinase effectors, leaving others untouched.

Buchmeier et al.[84] showed that mutants of S. enterica lacking RecA or RecBC protein function are highly sensitive to oxidative compounds synthesized by macrophages, and furthermore these findings indicate that successful systemic infection by S. enterica requires RecA- and RecBC-mediated recombinational repair of DNA damage.

For example, as Baumler et al. have suggested, Salmonella most likely evolved through horizontal gene transfer, and through the formation of new serovars due to additional pathogenicity islands, and through an approximation of its ancestry.

Newport shows signs of adaptation to a plant-colonization lifestyle, which may play a role in its disproportionate association with food-borne illness linked to produce.

Newport, contributes to the strain's fitness in tomatoes, and has homologs in the genomes of other Enterobacteriaceae that are able to colonize plant and animal hosts.

These developments were enabled by the discovery of the first generalized transducing phage P22[94] in S. Typhimurium, that allowed quick and easy genetic editing.

[96] As a natural alternative to traditional antimicrobials, phages are being recognised as highly effective control agents for Salmonella and other foodborne bacteria.