The QseBC Quorum Sensing System is Involved in Salmonella enterica serovar Typhimurium Colonization of the Swine Gastrointestinal Tract

The response of bacteria to hormone-like, chemical molecules is termed quorum sensing, a mechanism for cell-to-cell communication that includes sensing the host environment. In the gastromtestinal tract, at least two quorum sensing molecules are present that activate the bacterial QseBC quorum sensing system. autoinducer-3 (AI-3) and norepinephrine (NE). Al-3 is produced by bacteria, whereas NE is produced by the host, often during stress. We have demonstrated that the motility of Salmonella enterica serovar Typhimurium is enhanced in the presence of NE and 10% pre-conditioned medium (AI-3) from the wild-type strain

Serological Response of Swine to an Attenuated Salmonella enterica serovar Typhimurium Strain that Reduces Gastrointestinal Colonization, Fecal Shedding and Disease due to Virulent Salmonella Typhimurium

Swine are often asymptomatic carriers of Salmonella spp. Interventions are needed to limit Salmonella colonization of swine to enhance food safety. An attenuated Salmonella enterica serovar Typhimurium mutant strain (BBS 202) was tested in swine to determine whether vaccination could provide protection against wild-type S. Typhimurium challenge. Two groups of piglets (n=14/group) received an intranasal inoculation of BBS 202 or a PBS placebo at 6-weeks of age with a booster 2-weeks later. At 11-weeks of age, all pigs were challenged with the parental, wild-type S. Typhimurium by intranasal inoculation

Associations of the porcine immune response and genetic polymorphisms with the shedding of Salmonella enterica serovar Typhimurium

A major focus of our collaborattve research is to investigate the porctne response to Infection with Salmonella to 1) identify porctne genes differentially regulated during Infection and 2) Identify and associate genetic polymorphisms within these genes with infection status across swine populations In the current study, 40 crossbred pigs were intranasally inoculated with Salmonella enterica serovar Typhimurium and monitored for Salmonella fecal shedding and blood 1mmune parameters at 2, 7, 14 and 20 days post-inoculation (dpi). Using a multivariate permutation test, a positive correlation was observed between Salmonella shedding and Interferon-gamma (IFNG) levels at 2 and 7 dpi (p\u3c0.05), with a greater number of Salmonella shedding 1n the animals with higher IFNG levels

Differences in Pathogenesis for Salmonella enterica serovar Typhimurium in the Mouse Versus the Swine Model Identifies Bacterial Gene Products Required for Systemic but not Gastrointestinal Disease

Over the last several decades, the mouse model of typhoid fever has been an extremely productive model to investigate Salmonella enterica serovar Typhimurium (S Typhimurium) pathogenesis. The mouse is the paradigm for investigating systemic disease due to infection by Salmonella; however, the swine model of gastrointestinal colonization and enteric disease due to Salmonella is better suited to address food safety. Although certain Salmonella mutants may be attenuated for colonization and disease in both the mouse and swine model, others may only be attenuated in one of the models depending on whether the gene product is required for gastrointestinal or systemic disease. Recent research performed on the swine model in our laboratories with comparison to the literature on the mouse model, illustrates the discrepancy between these two models

Oxygen and nitrate-dependent regulation of dmsABC operon expression in Escherichia coli: sites for Fnr and NarL protein interactions

BACKGROUND: Escherichia coli can respire anaerobically using dimethyl sulfoxide (DMSO) or trimethylamine-N-oxide (TMAO) as the terminal electron acceptor for anaerobic energy generation. Expression of the dmsABC genes that encode the membrane-associated DMSO/TMAO reductase is positively regulated during anaerobic conditions by the Fnr protein and negatively regulated by the NarL protein when nitrate is present. RESULTS: The regions of dmsA regulatory DNA required for Fnr and NarL interactions in response to anaerobiosis and nitrate, respectively, were examined. Mutations within the Fnr site that deviated from the wild type sequence, TTGATaccgAACAA, or that removed an entire half-site, either impaired or abolished the anaerobic activation of dmsA-lacZ expression. The region for phosphorylated NarL (NarL-phosphate) binding at the dmsA promoter was identified by DNase I and hydroxyl radical footprinting methods. A large 97 bp region that overlaps the Fnr and RNA polymerase recognition sites was protected by NarL-phosphate but not by the non-phosphorylated form of NarL. Hydroxyl radical footprinting analysis confirmed the NarL-phosphate DNase I protections of both dmsA strands and revealed 8–9 protected sites of 3–5 bp occurring at ten bp intervals that are offset by 3 bp in the 3' direction. CONCLUSION: These findings suggest that multiple molecules of phosphorylated NarL bind along one face of the DNA and may interfere with Fnr and/or RNA polymerase interactions at the dmsA regulatory region. The interplay of these transcription factors insures a hierarchical expression of the dmsABC genes when respiration of the preferred electron acceptors, oxygen and nitrate, is not possible

Transcriptional response of blood leukocytes from turkeys challenged with Salmonella enterica serovar Typhimurium UK1

Non-typhoidal Salmonella is one of the most common causes of bacterial foodborne disease and consumption of contaminated poultry products, including turkey, is one source of exposure. Minimizing Salmonella colonization of commercial turkeys could decrease the incidence of Salmonella-associated human foodborne illness. Understanding host responses to these bacteria is critical in developing strategies to minimize colonization and reduce food safety risk. In this study, we evaluated bacterial load and blood leukocyte transcriptomic responses of 3-week-old turkeys challenged with the Salmonella enterica serovar Typhimurium (S. Typhimurium) UK1 strain. Turkeys (n = 8/dose) were inoculated by oral gavage with 108 or 1010 colony forming units (CFU) of S. Typhimurium UK1, and fecal shedding and tissue colonization were measured across multiple days post-inoculation (dpi). Fecal shedding was 1–2 log10 higher in the 1010 CFU group than the 108 CFU group, but both doses effectively colonized the crop, spleen, ileum, cecum, colon, bursa of Fabricius and cloaca without causing any detectable clinical signs in either group of birds. Blood leukocytes were isolated from a subset of the birds (n = 3–4/dpi) both pre-inoculation (0 dpi) and 2 dpi with 1010 CFU and their transcriptomic responses assayed by RNA-sequencing (RNA-seq). At 2 dpi, 647 genes had significant differential expression (DE), including large increases in expression of immune genes such as CCAH221, IL4I1, LYZ, IL13RA2, IL22RA2, and ACOD1. IL1β was predicted as a major regulator of DE in the leukocytes, which was predicted to activate cell migration, phagocytosis and proliferation, and to impact the STAT3 and toll-like receptor pathways. These analyses revealed genes and pathways by which turkey blood leukocytes responded to the pathogen and can provide potential targets for developing intervention strategies or diagnostic assays to mitigate S. Typhimurium colonization in turkeys

Impact of temperature and hydraulic retention time on pathogen and nutrient removal in woodchip bioreactors

Woodchip denitrification bioreactors are an important edge-of-field practice for treating agricultural drainage; however, their ability to filter microbial pollutants has primarily been explored in the context of wastewater treatment. Upflow column reactors were constructed and tested for E. coli, Salmonella, NO3-N, and dissolved reactive phosphorus (DRP) at hydraulic retention times (HRTs) of 12 and 24 h and at controlled temperatures of 10 and 21.5 °C. Influent solution was spiked to 30 mg L−1 NO3-N, 2–8 × 105 E. coli and Salmonella, and 0.1 mg L−1 DRP. Microbial removal was consistently observed with removal ranging from 75 to 78% reduction at 10 °C and 90–96% at 21.5 °C. The concentration reduction ranged from 2.75 to 9.03 × 104 for both organisms. HRT had less impact on microbial removal than temperature and thus further investigation of removal under lower HRTs is warranted. Nitrate concentrations averaged 96% reduction (with load removal of 14.6 g N m−3 d−1) from 21.5 °C columns at 24 HRT and 29% reduction (with load removal of 8.8 g N m−3 d−1) from 10 °C columns at 12 HRT. DRP removal was likely temporary due to microbial uptake. While potential for removal of E. coli and Salmonella by woodchip bioreactors is demonstrated, system design will need to be considered. High concentrations of these microbial contaminants are likely to occur during peak flows, when bypass flow may be occurring. The results of this study show that woodchip bioreactors operated for nitrate removal have a secondary benefit through the removal of enteric bacteria

Capsular polysaccharide production and serum survival of Vibrio vulnificus are dependent on antitermination control by RfaH

© 2016 Federation of European Biochemical Societies The human pathogen Vibrio vulnificus undergoes phase variation among colonial morphotypes, including a virulent opaque form which produces capsular polysaccharide (CPS) and a translucent phenotype that produces little or no CPS and is attenuated. Here, we found that a V. vulnificus mutant defective for RfaH antitermination control showed a diminished capacity to undergo phase variation and displayed significantly reduced distal gene expression within the Group I CPS operon. Moreover, the rfaH mutant produced negligible CPS and was highly sensitive to killing by normal human serum, results which indicate that RfaH is likely essential for virulence in this bacterium

TLR4 Single Nucleotide Polymorphisms (SNPs) Associated with Salmonella Shedding in Pigs

Toll-like receptor 4 (TLR4) is a key factor in the innate immune recognition of lipopolysaccharide (LPS) from Gram-negative bacteria. Previous studies from our group identified differences in the expression profile of TLR4 and genes affected by the TLR4 signaling pathway among pigs that shed varying levels of Salmonella, a Gram-negative bacterium. Therefore, genetic variation in this gene may be involved with the host’s immune response to bacterial infections. The current study screened for single nucleotide polymorphisms (SNPs) in the TLR4 gene and tested their association with Salmonella fecal shedding

Genomic and phenotypic characterization of multidrug-resistant Salmonella enterica serovar Reading isolates involved in a turkey-associated foodborne outbreak

Salmonella is a global bacterial foodborne pathogen associated with a variety of contaminated food products. Poultry products are a common source of Salmonella-associated foodborne illness, and an estimated 7% of human illnesses in the United States are attributed to turkey products. From November 2017 to March 2019, the Centers for Disease Control and Prevention reported a turkey-associated outbreak of multidrug-resistant (MDR; resistant to ≥3 antimicrobial classes) Salmonella enterica serovar Reading (S. Reading) linked to 358 human infections in 42 US states and Canada. Since S. Reading was seldom linked to human illness prior to this outbreak, the current study compared genomic sequences of S. Reading isolates prior to the outbreak (pre-outbreak) to isolates identified during the outbreak period, focusing on genes that were different between the two groups but common within a group. Following whole-genome sequence analysis of five pre-outbreak and five outbreak-associated turkey/turkey product isolates of S. Reading, 37 genes located within two distinct chromosomal regions were identified only in the pre-outbreak isolates: (1) an ~5 kb region containing four protein-coding genes including uidA which encodes beta-glucuronidase, pgdA encoding peptidoglycan deacetylase, and two hypothetical proteins and (2) an ~28 kb region comprised of 32 phage-like genes and the xerC gene, which encodes tyrosine recombinase (frequently associated with phage genes). The five outbreak isolates also had a deletional event within the cirA gene, introducing a translational frame shift and premature stop codon. The cirA gene encodes a protein with dual receptor functions: a siderophore receptor for transport of dihydroxybenzoylserine as well as a colicin Ia/b receptor. Significant differences for the identified genetic variations were also detected in 75 S. Reading human isolates. Of the 41 S. Reading isolates collected before or in 2017, 81 and 90% of the isolates contained the uidA and pgdA genes, respectively, but only 24% of the isolates collected after 2017 harbored the uidA and pgdA genes. The truncation event within the cirA gene was also significantly higher in isolates collected after 2017 (74%) compared to before or in 2017 (5%). Phenotypic analysis of the S. Reading isolates for colicin and cefiderocol sensitivities (CirA) and β-methyl-D-glucuronic acid utilization (UidA and accessory proteins) supported the genomic data. Overall, a similar genome reduction pattern was generally observed in both the turkey and human isolates of S. Reading during the outbreak period, and the genetic differences were present in genes that could potentially promote pathogen dissemination due to variation in Salmonella colonization, fitness, and/or virulence