Infection of Mice by Salmonella enterica Serovar Enteritidis Involves Additional Genes That Are Absent in the Genome of Serovar Typhimurium

Abstract

Salmonella enterica serovar Enteritidis causes a systemic, typhoid-like infection in newly hatched poultry and mice. In the present study, a library of 54,000 transposon mutants of S. Enteritidis phage type 4 (PT4) strain P125109 was screened for mutants deficient in the in vivo colonization of the BALB/c mouse model using a microarray-based negative-selection screening. Mutants in genes known to contribute to systemic infection (e.g., Salmonella pathogenicity island 2 [SPI-2], aro, rfa, rfb, phoP, and phoQ) and enteric infection (e.g., SPI-1 and SPI-5) in this and other Salmonella serovars displayed colonization defects in our assay. In addition, a strong attenuation was observed for mutants in genes and genomic islands that are not present in S. Typhimurium or in most other Salmonella serovars. These genes include a type I restriction/modification system (SEN4290 to SEN4292), the peg fimbrial operon (SEN2144A to SEN2145B), a putative pathogenicity island (SEN1970 to SEN1999), and a type VI secretion system remnant SEN1001, encoding a hypothetical protein containing a lysin motif (LysM) domain associated with peptidoglycan binding. Proliferation defects for mutants in these individual genes and in exemplar genes for each of these clusters were confirmed in competitive infections with wild-type S. Enteritidis. A ⌬SEN1001 mutant was defective for survival within RAW264.7 murine macrophages in vitro. Complementation assays directly linked the SEN1001 gene to phenotypes observed in vivo and in vitro. The genes identified here may perform novel virulence functions not characterized in previous Salmonella models.

Salmonella Persistence in Tomatoes Requires a Distinct Set of Metabolic Functions Identified by Transposon Insertion Sequencing

“…Besides being involved in the synthesis of arginine, the urea cycle is also involved in the incorporation of excess nitrogen. (37,38,51). Key metabolic steps are shown as shaded boxes.…”

“…Frequency of the GO terms in the genome is shown in gray, and frequency of the GO terms required for tomato colonization is shown in orange. (C) GO term enrichment analysis for those required for systemic infection in mice, showing frequency (%) in the genome and in screenings (37,38,51). Only significant terms (Bonferroni correction, P Ͻ 0.05) are shown.…”

“…Salmonella mutants in amino acid biosynthesis genes had the most pronounced phenotype in tomatoes but were not required for murine systemic infection, as determined in high-throughput screenings (37,38,51) and competition assays with isogenic mutants (52). We focused on this group of genes to explore the differences between the requirements for interactions with animals and plants.…”

Mouse models for assessing the cross-protective efficacy of oral non-typhoidal Salmonella vaccine candidates harbouring in-frame deletions of the ATP-dependent protease lon and other genes

“…2c). This is in part because a recent study showed that in a BALB/c mouse model of NTS infection, S. Enteritidis had greater numbers of serovarspecific virulence genes that were absent in the genome of S. Typhimurium (Silva et al, 2012).…”

A Novel Phage Element of Salmonella enterica Serovar Enteritidis P125109 Contributes to Accelerated Type III Secretion System 2-Dependent Early Inflammation Kinetics in a Mouse Colitis Model

“…The functions of most of the S. Enteritidis genes, those shared with extensively studied S. Typhimurium, are now know; however, the extra gene elements present in S. Enteritidis have yet to be explored for their functional importance. There are few reports addressing the roles of S. Enteritidis-specific gene elements in the invasiveness and pathogenicity of the serovar (39). The SEN1975 gene has been reported as a novel virulence factor of S. Enteritidis that modulates the host immune response, as it bears close homology with the mammalian Toll/interleukin-1 (IL-1) receptor family of proteins (30).…”