typhoidal and non-typhoidal Salmonella enterica serovars

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.Salmonella enterica is a highly diverse Gram negative bacterial species containing more than 2600 different serovars differentiated by their antigenic presentation. Various serovars are characterized by their host specificity or by the clinical syndrome they cause ranging from asymptomatic carriage to invasive systemic disease. Most S. enterica serovars associated with diseases in humans and other warm blooded animals belong to subspecies I consisting of both typhoidal and non-typhoidal serovars. Several excellent recent reviews have highlighted different aspects of invasive salmonellosis (De Jong et al., 2012Feasey et al., 2012), discussed the mechanisms behind host restriction (Baumler and Fang, 2013), and detailed salmonelloses in immunocompromised individuals (Gordon, 2008Maclennan, 2014). Here, we will discuss how typhoidal and non-typhoidal serovars differ in epidemiology, clinical manifestations, and the immune response they trigger in humans.