Embracing Diversity: Differences in Virulence Mechanisms, Disease Severity, and Host Adaptations Contribute to the Success of Nontyphoidal Salmonella as a Foodborne Pathogen

Abstract

Not all Salmonella enterica serovars cause the same disease. S. enterica represents an incredibly diverse species comprising >2,600 unique serovars. While some S. enterica serovars are host-restricted, others infect a wide range of hosts. The diseases that nontyphoidal Salmonella (NTS) serovars cause vary considerably, with some serovars being significantly more likely to cause invasive disease in humans than others. Furthermore, while genomic analyses have advanced our understanding of the genetic diversity of these serovars, they have not been able to fully account for the observed clinical differences. One overarching challenge is that much of what is known about Salmonella ’s general biology and virulence strategies is concluded from studies examining a select few serovars, especially serovar Typhimurium. As targeted control strategies have been implemented to control select serovars, an increasing number of foodborne outbreaks involving serovars that are less frequently associated with human clinical illness are being detected. Harnessing what is known about the diversity of NTS serovars represents an important factor in achieving the ultimate goal of reducing salmonellosis-associated morbidity and mortality worldwide. In this review we summarize the current understanding of the differences and similarities among NTS serovars, highlighting the virulence mechanisms, genetic differences, and sources that characterize S. enterica diversity and contribute to its success as a foodborne pathogen.

Comparing serotyping with whole-genome sequencing for subtyping of non-typhoidal Salmonella enterica: a large-scale analysis of 37 serotypes with a public health impact in the USA

“…Serotyping has been used for many years for the subtyping of Salmonella isolates based on the immunological variability of two main surface structures, namely the O (somatic) and the H (flagellar) antigens [3]. Based on to the Kauffmann–White–Le Minor scheme, more than 2600 serotypes had been identified up to 2019; of these, approximately 1600 belong to the subspecies enterica (subspecies I), which is the subspecies involved in the vast majority of the foodborne zoonotic salmonellosis caused by non-typhoidal Salmonella (NTS) [4]. Even though many serotypes may contribute to human illness, the 20 most prevalent serotypes account for almost 70 % of the reported human cases in the USA according to a Centers for Disease Control and Prevention (CDC) report [5].…”

Genomic characterization and phylogenetic analysis ofSalmonella entericaserovar Javiana

“…Salmonella virulence factors aid in host colonization and pathogenicity by assisting the pathogen in attaching to, invading, and replicating within host cells, intra-and extracellular survival, evading host defenses, and outcompeting the gut microbiome and include adhesion systems, capsule, flagella, and toxins ( Jajere, 2019 ). Virulence factors and related genes are frequently clustered together in pathogenicity islands, which are often found on mobile genetic elements (MGEs), such as plasmids and prophages ( Cheng, Eade & Wiedmann, 2019 ; Jacobsen et al, 2011 ). Eight Salmonella Pathogenicity Islands (SPIs) or islets (SPI-1, SPI-2, SPI-4, SPI-5, SPI-9, SPI-11, SPI-12, and CS54) are commonly found in most non-typhoidal serovars ( Den Bakker et al, 2011 ; Jacobsen et al, 2011 ).…”

“…C63PI, which is located within SPI-1, contains the sit operon that encodes an iron uptake system ( Schmidt & Hensel, 2004 ; Zhou, Hardt & Galán, 1999 ). SPI-13 has been associated with macrophage internalization and virulence in chickens and mice ( Cheng, Eade & Wiedmann, 2019 ; Elder et al, 2016 ; Espinoza et al, 2017 ; Shah et al, 2005 ). SPI-14 is involved in epithelial invasion and pathogenicity in chickens ( Cheng, Eade & Wiedmann, 2019 ; Fookes et al, 2011 ; Shah et al, 2005 ).…”

“…SPI-13 has been associated with macrophage internalization and virulence in chickens and mice ( Cheng, Eade & Wiedmann, 2019 ; Elder et al, 2016 ; Espinoza et al, 2017 ; Shah et al, 2005 ). SPI-14 is involved in epithelial invasion and pathogenicity in chickens ( Cheng, Eade & Wiedmann, 2019 ; Fookes et al, 2011 ; Shah et al, 2005 ). Most of the representative subset of TN isolates analyzed for SPI contained SPI-2 and SPI-4.…”

Spatial and space-time clustering and demographic characteristics of human nontyphoidal Salmonella infections with major serotypes in Toronto, Canada

“…On a worldwide level, diarrheal and invasive infections caused by NTS have the highest yearly disease burden among all foodborne infections, with 4.07 million attributable Disability Adjusted Life Years [ 2 ]. Among the more than 2,600 currently known NTS serotypes, only a small portion cause human infection, most commonly gastroenteritis [ 3 , 4 ]. In Canada, NTS serotype Enteritidis ( S .…”