Abstract
Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) is a Gram-negative bacterium with a broad host range that causes non-typhoidal salmonellosis in humans. S. Typhimurium infects epithelial cells and macrophages in the small intestine where it replicates in a specialized intracellular niche called the Salmonella-containing vacuole (SCV) and promotes inflammation of the mucosa to induce typically self-limiting gastroenteritis. Virulence and spread of the bacterium is determined in part by the host individual's ability to limit the infection through innate immune responses at the gastrointestinal mucosa, including programmed cell death. S. Typhimurium however, has evolved a myriad of mechanisms to counteract or exploit host responses through the use of Type III Secretion Systems (T3SS), which allow the translocation of virulence (effector) proteins into the host cell for the benefit of optimal bacterial replication and dissemination. T3SS effectors have been found to interact with apoptotic, necroptotic, and pyroptotic cell death cascades, interfering with both efficient clearance of the bacteria and the recruitment of neutrophils or dendritic cells to the area of infection. The interplay of host inflammation, programmed cell death responses, and bacterial defenses in the context of non-typhoidal Salmonella (NTS) infection is a continuing area of interest within the field, and as such has been reviewed here.
Highlights
Reviewed by: Silvia Guglietta, Medical University of South Carolina, United States Elsa Anes, University of Lisbon, Portugal
Typhimurium infects epithelial cells and macrophages in the small intestine where it replicates in a specialized intracellular niche called the Salmonella-containing vacuole (SCV) and promotes inflammation of the mucosa to induce typically self-limiting gastroenteritis
Typhimurium showed similar levels of caspase3/-7 activation when compared to wild type (WT) infection, but resulted in higher levels of mixed lineage kinase domain-like protein (MLKL) phosphorylation, indicating that Salmonella secreted effector K1 (SseK1) and SseK3 may inhibit necroptotic cell death [83]
Summary
Infections caused by Salmonella enterica are a major challenge in both human and animal health. Enterica serovars are categorized by their disease phenotypes into typhoidal (Typhi and Paratyphi) and non-typhoidal Salmonella (NTS) serovars Typhoidal serovars cause invasive disease and are human restricted, NTS serovars cause disease in a wide range of mammals and birds and typically cause self-limiting gastroenteritis (salmonellosis) in humans, with the bacteria restricted to the gastrointestinal mucosa [1, 2]. S. Typhimurium is acquired via the fecal-oral route from consumption of raw or contaminated poultry products, and causes the majority of notified NTS infections in Australia [3, 4]
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