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. 2014 Aug 4;5:391.
doi: 10.3389/fmicb.2014.00391. eCollection 2014.

Same Species, Different Diseases: How and Why Typhoidal and Non-Typhoidal Salmonella Enterica Serovars Differ

Free PMC article

Same Species, Different Diseases: How and Why Typhoidal and Non-Typhoidal Salmonella Enterica Serovars Differ

Ohad Gal-Mor et al. Front Microbiol. .
Free PMC article


Human infections by the bacterial pathogen Salmonella enterica represent major disease burdens worldwide. This highly ubiquitous species consists of more than 2600 different serovars that can be divided into typhoidal and non-typhoidal Salmonella (NTS) serovars. Despite their genetic similarity, these two groups elicit very different diseases and distinct immune responses in humans. Comparative analyses of the genomes of multiple Salmonella serovars have begun to explain the basis of the variation in disease manifestations. Recent advances in modeling both enteric fever and intestinal gastroenteritis in mice will facilitate investigation into both the bacterial- and host-mediated mechanisms involved in salmonelloses. Understanding the genetic and molecular mechanisms responsible for differences in disease outcome will augment our understanding of Salmonella pathogenesis, host immunity, and the molecular basis of host specificity. This review outlines the differences in epidemiology, clinical manifestations, and the human immune response to typhoidal and NTS infections and summarizes the current thinking on why these differences might exist.

Keywords: NTS; Salmonella enterica; enteric fever; gastroenteritis; salmonellosis; typhoid.


Molecular bases for differences between typhoidal and NTS serovars. (A) Typhoidal serovars possess several inactive/degraded genes compared to NTS serovars such as genes for chemotaxis, adhesion, and anaerobic metabolism. (B) Both typhoidal and NTS serovars possess unique virulence factors. For example, some S. Typhi strains express Vi capsule that reduces TLR-dependent IL-8 production in the intestinal mucosa. However, while the Vi capsule plays a role in typhoid fever manifestation, it is not necessary as it is absent from other typhoidal serovars and Vi-negative mutants of S. Typhi are still able to cause a typhoid-like illness in humans. (C) In contrast to typhoidal serovars, NTS cause severe intestinal inflammation. NTS serovars have evolved to utilize inflammation-derived metabolites (e.g., nitrate and tetrathionate), thereby enhancing their growth in the inflamed intestine. Typhoidal serovars have lost the ability to benefit from inflammation-derived metabolites and disseminate to systemic sites to a much greater extent.

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