Salmonella  is a Gram-negative facultative rod-shaped bacterium in the same proteobacterial family as Escherichia coli, the family Enterobacteriaceae, trivially known as "enteric" bacteria. Salmonella is nearly as well-studied as E. coli from a structural, biochemical and molecular point of view, and as poorly understood as E. coli from an ecological point of view. Salmonellae live in the intestinal tracts of warm and cold blooded animals. Some species are ubiquitous. Other species are specifically adapted to a particular host. In humans, Salmonella are the cause of two diseases called salmonellosis: enteric fever (typhoid), resulting from bacterial invasion of the bloodstream, and acute gastroenteritis, resulting from a foodborne infection/intoxication.At the beginning of the 19th century, typhoid was defined on the basis of clinical signs and symptoms and pathological (anatomical) changes. However, at this time, all sorts of enteric fevers were characterized as "typhoid". 

Salmonella typhi

Nowadays in developed countries, salmonella is commonly associated with acute non-systemic gastroenteritis. But certain serovars of Salmonella, such as S.typhi and S. paratyphi are important as the causative agent of typhoid fever that is a common diseases in developing countries. Typhoid fever caused by Salmonella enterica serover Typhi (S. Typhi) is responsible for an estimated 21.7 million cases per year worldwide.Recent reports indicate that the incidence of paratyphoid A fever is on the rise in areas of endemicity (e.g., South and Southeast Asia and China) and among travelers returning from those areas.The emergence of multiple antibiotic-resistant Salmonella strains has further increased the health risks posed by these infections.

Recent studies have shown the importance of the role of porins in bacterial pathogenesis and ability of them in promoting of humoral and cellular immune system in host. Nowadays there are many approaches to design vaccines, but we need new methods to access vaccines with better quality, less complications and more effectiveness. Due to the severity of the disease, relapse and spread through asymptomatic carriers, the incidence of drug resistance and use as a biological weapon, Salmonella has become a serious threat. Therefore in some study  try to design a new multiepitopic recombinant protein as a candidate model for new generation of vaccine against Salmonella typhi.

References:

[1]Mathur, R. et al. A mouse model of Salmonella Typhi infection. Cell 151, 590–602 (2012)

[2]Sztein, M.B., Bafford, A.C. & Salerno-Goncalves, R. Salmonella enterica serovar Typhi exposure elicits ex vivo cell-type-specific epigenetic changes in human gut cells. Sci Rep 10, 13581 (2020). 

[3]http://textbookofbacteriology.net/salmonella.html

[4]https://www.nature.com/articles/mi201524

[5]https://systems.enpress-publisher.com/index.php/ti/article/view/891