Sodium butyrate modulates chicken macrophage proteins essential for Salmonella Enteritidis invasion

Salmonella Enteritidis is an intracellular foodborne pathogen that has developed multiple mechanisms to alter poultry intestinal physiology and infect the gut. Short chain fatty acid butyrate is derived from microbiota metabolic activities, and it maintains gut homeostasis. There is limited understanding on the interaction between S. Enteritidis infection, butyrate, and host intestinal response. To fill this knowledge gap, chicken macrophages (also known as HTC cells) were infected with S. Enteritidis, treated with sodium butyrate, and proteomic analysis was performed. A growth curve assay was conducted to determine sub-inhibitory concentration (SIC, concentration that do not affect bacterial growth compared to control) of sodium butyrate against S. Enteritidis. HTC cells were infected with S. Enteritidis in the presence and absence of SIC of sodium butyrate. The proteins were extracted and analyzed by tandem mass spectrometry. Our results showed that the SIC was 45 mM. Notably, S. Enteritidis-infected HTC cells upregulated macrophage proteins involved in ATP synthesis through oxidative phosphorylation such as ATP synthase subunit alpha (ATP5A1), ATP synthase subunit d, mitochondrial (ATP5PD) and cellular apoptosis such as Cytochrome-c (CYC). Furthermore, sodium butyrate influenced S. Enteritidis-infected HTC cells by reducing the expression of macrophage proteins mediating actin cytoskeletal rearrangements such as WD repeat-containing protein-1 (WDR1), Alpha actinin-1 (ACTN1), Vinculin (VCL) and Protein disulfide isomerase (P4HB) and intracellular S. Enteritidis growth and replication such as V-type proton ATPase catalytic subunit A (ATPV1A). Interestingly, sodium butyrate increased the expression of infected HTC cell protein involving in bacterial killing such as Vimentin (VIM). In conclusion, sodium butyrate modulates the expression of HTC cell proteins essential for S. Enteritidis invasion.

RpoS-regulated SEN1538 gene promotes resistance to stress and influences Salmonella enterica serovar enteritidis virulence

Salmonella enterica serovar Enteritidis (S. Enteritidis; wild type (WT)) is a major cause of foodborne illness globally. The ability of this pathogen to survive stress inside and outside the host, such as encountering antimicrobial peptides and heat stress, determines the efficiency of enteric infection. These stressors concertedly trigger virulence factors encoded on Salmonella pathogenicity islands (SPIs). Although RpoS is a well-known central transcriptional stress and virulence regulator, functional information regarding the genes of the regulon is currently limited. Here, we identified SEN1538 as a conserved RpoS-regulated gene belonging to the KGG protein superfamily. We further assessed its role in pathogenic stress responses and virulence. When SEN1538 was deleted (Δ1538), the pathogen showed reduced survival during antimicrobial peptide introduction and heat stress at 55°C compared to WT. The mutant displayed 70% reduced invasion in the HCT116 colon epithelial cell line, 5-fold attenuated phagocytic survival in RAW264.7 cells, and downregulation of several SPI-1 and SPI-2 genes encoding the three secretion system apparatus and effector proteins. Δ1538 also showed decreased virulence compared to WT, demonstrated by its reduced bacterial counts in the feces, mLN, spleen, and cecum of C57BL/6 mice. Comparative transcriptomic analysis of Δ1538 against WT revealed 111 differentially regulated genes, 103 of which were downregulated (fold change ≤ -1.5, P < 0.05). The majority of these genes were in clusters for metabolism, transporters, and pathogenesis, driving pathogenic stress responses and virulence. SEN1538 is, therefore, an important virulence determinant contributing to the resilience of S. Enteritidis to stress factors during infection.

A ROD9 island encoded gene in Salmonella Enteritidis plays an important role in acid tolerance response and helps in systemic infection in mice

Salmonella, like other pathogenic bacteria has undergone multiple genomic alterations to adapt itself into specific host environments executing varied degrees of virulence through evolution. Such variations in genome content have been assumed to lead the closely related non-typhoidal serovars, S. Enteritidis, and S. Typhimurium to exhibit Type Three Secretion System -2 (T3SS-2) based diverse colonization and inflammation kinetics. Mutually exclusive genes present in either of the serovars are recently being studied and in our currentwork, we focused on a particular island ROD9, present in S. Enteritidis but not in S. Typhimurium. Earlier reports have identified a few genes from this island to be responsible for virulence in vitro as well as in vivo. In this study, we have identified another gene, SEN1008 from the same island encoding a hypothetical protein to be a potential virulence determinant showing systemic attenuation upon mutation in C57BL/6 mice infection model. The isogenic mutant strain displayed reduced adhesion to epithelial cells in vitro as well as was highly immotile. It was also deficient in intracellular replication in vitro, with a highly suppressed SPI-2and failed to cause acute colitis at 72-h p.i.in vivo. Moreover, on acid exposure, SEN1008 showed 17 folds and 2 fold up-regulations during adaptation and challenge phases,respectively and ΔSEN1008 failed to survive during ATR assay, indicating its role under acid stress. Together, our findings suggested ΔSEN1008 to be significantly attenuated and we propose this gene to be a potent factor responsible for S. Enteritidis pathogenesis.

Case Study of Emphysematous Osteomyelitis of Both Femoral Heads

Early references of emphysematous osteomyelitis (EO) in the literature trace back to 1981, when the presence of intraosseous gas was mentioned in a paper of Ram et al.. Subsequently, 48 cases of EO were described. A significant underlying comorbidity was reported in most EO cases, especially diabetes and malignancy. This report presents a 37-year-old male with undiagnosed diabetes mellitus which was accompanied by emphysematous osteomyelitis of both femoral heads.

Genomic analyses of multidrug-resistant Salmonella Indiana, Typhimurium, and Enteritidis isolates using MinION and MiSeq sequencing technologies

We sequenced 25 isolates of phenotypically multidrug-resistant Salmonella Indiana (n = 11), Typhimurium (n = 8), and Enteritidis (n = 6) using both MinION long-read [SQK-LSK109 and flow cell (R9.4.1)] and MiSeq short-read (Nextera XT and MiSeq Reagent Kit v2) sequencing technologies to determine the advantages of each approach in terms of the characteristics of genome structure, antimicrobial resistance (AMR), virulence potential, whole-genome phylogeny, and pan-genome. The MinION reads were base-called in real-time using MinKnow 3.4.8 integrated with Guppy 3.0.7. The long-read-only assembly, Illumina-only assembly, and hybrid assembly pipelines of Unicycler 0.4.8 were used to generate the MinION, MiSeq, and hybrid assemblies, respectively. The MinION assemblies were highly contiguous compared to the MiSeq assemblies but lacked accuracy, a deficiency that was mitigated by adding the MiSeq short reads through the Unicycler hybrid assembly which corrected erroneous single nucleotide polymorphisms (SNPs). The MinION assemblies provided similar predictions of AMR and virulence potential compared to the MiSeq and hybrid assemblies, although they produced more total false negatives of AMR genotypes, primarily due to failure in identifying tetracycline resistance genes in 11 of the 19 MinION assemblies of tetracycline-resistant isolates. The MinION assemblies displayed a large genetic distance from their corresponding MiSeq and hybrid assemblies on the whole-genome phylogenetic tree, indicating that the lower read accuracy of MinION sequencing caused incorrect clustering. The pan-genome of the MinION assemblies contained significantly more accessory genes and less core genes compared to the MiSeq and hybrid assemblies, suggesting that although these assemblies were more contiguous, their sequencing errors reduced accurate genome annotations. Our research demonstrates that MinION sequencing by itself provides an efficient assessment of the genome structure, antimicrobial resistance, and virulence potential of Salmonella; however, it is not sufficient for whole-genome phylogenetic and pan-genome analyses. MinION in combination with MiSeq facilitated the most accurate genomic analyses.

Effect of sub-lethal chemical disinfection on the biofilm forming ability, resistance to antibiotics and expression of virulence genes of Salmonella Enteritidis biofilm-surviving cells

Although disinfection procedures are widely implemented in food environments, bacteria can survive and present increased virulence/resistance. Since little is known about these phenomena regarding biofilms, this study aimed to investigate the effect of chemical disinfection on biofilm-derived cells of Salmonella Enteritidis. Using a reference strain (NCTC 13349) and a food isolate (350), biofilm susceptibility to benzalkonium chloride (BAC), sodium hypochlorite (SH) and hydrogen peroxide (HP) was evaluated and biofilms were exposed to sub-lethal concentrations of each disinfectant. Biofilm-derived cells were characterized for their biofilm forming ability, antibiotic resistance and expression of virulence-associated genes. Except for a few instances, disinfectant exposure did not alter antibiotic susceptibility. However, SH and HP exposure enhanced the biofilm forming ability of Salmonella Enteritidis NCTC 13349. After BAC and HP exposure, biofilm-derived cells presented a down-regulation of rpoS. Exposure to BAC also revealed an up-regulation of invA, avrA and csgD on Salmonella Enteritidis NCTC 13349. The results obtained suggest that biofilm-derived cells that survive disinfection may represent an increased health risk.

Sex pilus specific bacteriophage to drive bacterial population towards antibiotic sensitivity

Antimicrobial resistance (AMR) is now a major global problem largely resulting from the overuse of antibiotics in humans and livestock. In some AMR bacteria, resistance is encoded by conjugative plasmids expressing sex-pili that can readily spread resistance through bacterial populations. The aim of this study was to use sex pilus-specific (SPS) phage to reduce the carriage of AMR plasmids. Here, we demonstrate that SPS phage can kill AMR Escherichia coli and select for AMR plasmid loss in vitro. For the first time, we also demonstrate that SPS phage can both prevent the spread of AMR Salmonella Enteritidis infection in chickens and shift the bacterial population towards antibiotic sensitivity.

Transcriptional profiling of Salmonella enterica serovar Enteritidis exposed to ethanolic extract of organic cranberry pomace

Non-typhoidal Salmonella enterica serovars continue to be an important food safety issue worldwide. Cranberry (Vaccinium macrocarpon Ait) fruits possess antimicrobial properties due to their various acids and phenolic compounds; however, the underlying mechanism of actions is poorly understood. We evaluated the effects of cranberry extracts on the growth rate of Salmonella enterica serovars Typhimurium, Enteritidis and Heidelberg and on the transcriptomic profile of Salmonella Enteritidis to gain insight into phenotypic and transcriptional changes induced by cranberry extracts on this pathogen. An ethanolic extract from cranberry pomaces (KCOH) and two of its sub-fractions, anthocyanins (CRFa20) and non-anthocyanin polyphenols (CRFp85), were used. The minimum inhibitory (MICs) and bactericidal (MBCs) concentrations of these fractions against tested pathogens were obtained using the broth micro-dilution method according to the Clinical Laboratory Standard Institute’s guidelines. Transcriptional profiles of S. Enteritidis grown in cation-adjusted Mueller-Hinton broth supplemented with or without 2 or 4 mg/ml of KCOH were compared by RNASeq to reveal gene modulations serving as markers for biological activity. The MIC and MBC values of KCOH were 8 and 16 mg/mL, respectively, against all tested S. enterica isolates. The MIC value was 4 mg/mL for both CRFa20 and CRFp85 sub-fractions, and a reduced MBC value was obtained for CRFp85 (4 mg/ml). Treatment of S. Enteritidis with KCOH revealed a concentration-dependent transcriptional signature. Compared to the control, 2 mg/ml of KCOH exposure resulted in 89 differentially expressed genes (DEGs), of which 53 and 36 were downregulated and upregulated, respectively. The upregulated genes included those involved in citrate metabolism, enterobactin synthesis and transport, and virulence. Exposure to 4 mg/ml KCOH led to the modulated expression of 376 genes, of which 233 were downregulated and 143 upregulated, which is 4.2 times more DEGs than from exposure to 2 mg/ml KCOH. The downregulated genes were related to flagellar motility, Salmonella Pathogenicity Island-1 (SPI-1), cell wall/membrane biogenesis, and transcription. Moreover, genes involved in energy production and conversion, carbohydrate transport and metabolism, and coenzyme transport and metabolism were upregulated during exposure to 4 mg/ml KCOH. Overall, 57 genes were differentially expressed (48 downregulated and 9 upregulated) in response to both concentrations. Both concentrations of KCOH downregulated expression of hilA, which is a major SPI-1 transcriptional regulator. This study provides information on the response of Salmonella exposed to cranberry extracts, which could be used in the control of this important foodborne pathogen.

Synthetic and immunological studies of Salmonella Enteritidis O-antigen tetrasaccharides as potential anti-Salmonella vaccines

The first synthetic carbohydrate based potential anti-Salmonella Enteritidis vaccine has been developed by conjugating a synthetic tetrasaccharide antigen with bacteriophage Qβ. High levels of specific and long lasting anti-glycan IgG antibodies were induced by the conjugate, which completely protected mice from lethal bacterial challenges in a passive transfer model.

Invasive Nontyphoidal Salmonella Disease in Africa

Nontyphoidal salmonellae (NTS) are a major cause of invasive (iNTS) disease in sub-Saharan Africa, manifesting as bacteremia and meningitis. Available epidemiological data indicate that iNTS disease is endemic in much of the region. Antimicrobial resistance is common and case fatality rates are high. There are well-characterized clinical associations with iNTS disease, including young age, HIV infection, malaria, malnutrition, anemia, and sickle cell disease. However, the clinical presentation of iNTS disease is often with fever alone, so clinical diagnosis is impossible without blood culture confirmation. No vaccine is currently available, making this a priority area for global health research. Over the past ten years, it has emerged that iNTS disease in Africa is caused by distinct pathovars of Salmonella Typhimurium, belonging to sequence type ST313, and Salmonella Enteritidis. These are characterized by genome degradation and appear to be adapting to an invasive lifestyle. Investigation of rare patients with primary immunodeficiencies has suggested a key role for interferon gamma-mediated immunity in host defense against NTS. This concept has been supported by recent population-based host genetic studies in African children. In contrast, immunoepidemiological studies from Africa indicate an important role for antibody for protective immunity, supporting the development of antibody-inducing vaccines against iNTS disease. With candidate O-antigen-based vaccines due to enter clinical trials in the near future, research efforts should focus on understanding the relative contributions of antibody and cell-mediated immunity to protection against iNTS disease in humans.

IS26-mediated formation of a virulence and resistance plasmid in Salmonella Enteritidis

Objectives

To characterize a novel virulence-resistance plasmid pSE380T carried by a Salmonella enterica serotype Enteritidis clinical strain SE380.

Methods

The plasmid pSE380T was conjugated to Escherichia coli strain J53 and sequenced by PacBio RSII, followed by subsequent annotation and genetic analysis.

Results

Sequence analysis of this plasmid revealed that the entire Salmonella Enteritidis-specific virulence plasmid, pSEN, had been incorporated into an IncHI2 MDR plasmid, which comprises the cephalosporin and fosfomycin resistance determinants blaCTX-M-14 and fosA3. Based on BLAST analysis and scrutiny of insertion footprints, the insertion event was found to involve a replicative transposition process mediated by IS26, an IS element frequently detected in various resistance plasmids. The resulting pSE380T plasmid also comprises backbone elements of IncHI2 and IncFIA plasmids, producing a rare fusion product that simultaneously encodes functional features of both, i.e. virulence, resistance and high transmissibility.

Conclusions

This is a novel hybrid plasmid mediating MDR and virulence from a clinical Salmonella Enteritidis strain. This plasmid is likely to be transmissible amongst various serotypes of Salmonella and other Enterobacteriaceae species, rendering a wide range of bacterial pathogens resistant to cephalosporins and fosfomycin, and further enhancing their virulence potential. It will be important to monitor the spread and further evolution of this plasmid among the Enterobacteriaceae strains.

Role of the sseK1 gene in the pathogenicity of Salmonella enterica serovar enteritidis in vitro and in vivo

Salmonella enteritidis is a common food-borne pathogen associated with consumption of contaminated poultry meat and eggs, which frequently causes gastroenteritis in humans. Salmonella secreted effector K1 (SseK1), as a translocated and secreted protein has been identified to be essential for the virulence of Salmonella typhimurium in host cells. However, the role of the sseK1 gene in the pathogenicity of S. enteritidis remain unclear. In this study, a sseK1 deletion mutant of S. enteritidis was constructed and its biological characteristics were examined. It was found that the sseK1 deletion mutant did not affect the growth, adherence and invasion of Salmonella enteritidis when compared to the wild-type S. enteritidis. However, the mutant showed decreased formation of biofilm and significantly reduced intracellular survival of bacteria in activated mouse peritoneal macrophages, as well as showed reduced pathogenicity to a murine model by increasing the lethal dose 50% (LD₅₀) value and decreasing the proliferation ratio of bacteria in vivo. Taken together, this study determined an important role for SseK1 in the pathogenicity of S. enteritidis in vitro and in vivo.

Identification of a novel gene in ROD9 island of Salmonella Enteritidis involved in the alteration of virulence-associated genes expression

Salmonella enterica subsp. I serovar Enteritidis (S. Enteritidis), one of the causative agents for non-typhoidal gastrointestinal diseases in humans is an intracellular bacterium and mechanism for its invasion into host cells is critical to cause infection. The virulence of the pathogen is explained by the expression of genes located on its pathogenicity islands, mostly encoded under SPI-1 and SPI-2. However, S. Typhimurium SL1344, despite sharing ∼98% of its genome with S. Enteritidis P125109, lacks few regions of differences (ROD) that are hypothesized to impart virulence potential to S. Enteritidis. In this study, we created different mutants in the ROD9 island of S. Enteritidis, also referred as SPI-19 and identified a novel locus, SEN1005, encoding a hypothetical protein that is involved in its pathogenesis. ΔSEN1005 displayed significantly reduced entry into cultured epithelial cells as well as uptake by macrophages and failed to cause acute colitis in C57BL/6 mice at day 3 post-infection (p.i.). Additionally, the global transcriptome analysis revealed a highly repressed SPI-1 and other down-regulated genes responsible for flagellar assembly, chemotaxis and motility in the mutant which correlated with decreased invasion and abated inflammation as compared to the wild-type. Therefore, our findings revealed that ΔSEN1005 was attenuated in vitro as well as in vivo and we propose this hypothetical protein to play a role in altering the expression of genes involved in Salmonella virulence.

Lactobacillus bulgaricus, Lactobacillus rhamnosus and Lactobacillus paracasei Attenuate Salmonella Enteritidis, Salmonella Heidelberg and Salmonella Typhimurium Colonization and Virulence Gene Expression In Vitro

Salmonella Enteritidis (SE), Salmonella Typhimurium (ST), and Salmonella Heidelberg (SH) have been responsible for numerous outbreaks associated with the consumption of poultry meat and eggs. Salmonella colonization in chicken is characterized by initial attachment to the cecal epithelial cells (CEC) followed by dissemination to the liver, spleen, and oviduct. Since cecal colonization is critical to Salmonella transmission along the food chain continuum, reducing this intestinal association could potentially decrease poultry meat and egg contamination. Hence, this study investigated the efficacy of Lactobacillus delbreuckii sub species bulgaricus (NRRL B548; LD), Lactobacillus paracasei (DUP-13076; LP), and Lactobacillus rhamnosus (NRRL B442; LR) in reducing SE, ST, and SH colonization in CEC and survival in chicken macrophages. Additionally, their effect on expression of Salmonella virulence genes essential for cecal colonization and survival in macrophages was evaluated. All three probiotics significantly reduced Salmonella adhesion and invasion in CEC and survival in chicken macrophages (p < 0.05). Further, the probiotic treatment led to a significant reduction in Salmonella virulence gene expression (p < 0.05). Results of the study indicate that LD, LP, and LR could potentially be used to control SE, ST, and SH colonization in chicken. However, these observations warrant further in vivo validation.

Contribution of flagella and motility to gut colonisation and pathogenicity of Salmonella Enteritidis in the chicken

Salmonella Enteritidis causes fowl paratyphoid in poultry and is frequently associated to outbreaks of food-borne diseases in humans. The role of flagella and flagella-mediated motility into host-pathogen interplay is not fully understood and requires further investigation. In this study, one-day-old chickens were challenged orally with a wild-type strain Salmonella Enteritidis, a non-motile but fully flagellated (SE ΔmotB) or non-flagellated (SE ΔfliC) strain to evaluate their ability to colonise the intestine and spread systemically and also of eliciting gross and histopathological changes. SE ΔmotB and SE ΔfliC were recovered in significantly lower numbers from caecal contents in comparison with Salmonella Enteritidis at early stages of infection (3 and 5dpi). The SE ΔmotB strain, which synthesises paralysed flagella, showed poorer intestinal colonisation ability than the non-flagellated SE ΔfliC. Histopathological analyses demonstrated that the flagellated strains induced more intense lymphoid reactivity in liver, ileum and caeca. Thus, in the present study the flagellar structure and motility seemed to play a role in the early stages of the intestinal colonisation by Salmonella Enteritidis in the chicken.

The Salmonella Effector SpvD Is a Cysteine Hydrolase with a Serovar-specific Polymorphism Influencing Catalytic Activity, Suppression of Immune Responses, and Bacterial Virulence

Many bacterial pathogens secrete virulence (effector) proteins that interfere with immune signaling in their host. SpvD is a Salmonella enterica effector protein that we previously demonstrated to negatively regulate the NF-κB signaling pathway and promote virulence of S. enterica serovar Typhimurium in mice. To shed light on the mechanistic basis for these observations, we determined the crystal structure of SpvD and show that it adopts a papain-like fold with a characteristic cysteine-histidine-aspartate catalytic triad comprising Cys-73, His-162, and Asp-182. SpvD possessed an in vitro deconjugative activity on aminoluciferin-linked peptide and protein substrates in vitro A C73A mutation abolished SpvD activity, demonstrating that an intact catalytic triad is required for its function. Taken together, these results strongly suggest that SpvD is a cysteine protease. The amino acid sequence of SpvD is highly conserved across different S. enterica serovars, but residue 161, located close to the catalytic triad, is variable, with serovar Typhimurium SpvD having an arginine and serovar Enteritidis a glycine at this position. This variation affected hydrolytic activity of the enzyme on artificial substrates and can be explained by substrate accessibility to the active site. Interestingly, the SpvDG161 variant more potently inhibited NF-κB-mediated immune responses in cells in vitro and increased virulence of serovar Typhimurium in mice. In summary, our results explain the biochemical basis for the effect of virulence protein SpvD and demonstrate that a single amino acid polymorphism can affect the overall virulence of a bacterial pathogen in its host.

Salmonella Enterica Serotype Enteritidis Vertebral Osteomyelitis and Epidural Abscess Complicated with Meningitis

Infection with non-typhoidal Salmonella often results in a self-limited acute gastroenteritis. Extra-intestinal Salmonella infection is relatively rare and occurs predominantly in infants and adults with significant underlying conditions. We describe a 54-year-old Japanese man with a history of heavy alcohol consumption and daily contact with a dog, who developed bacteremia complicated by vertebral osteomyelitis, spinal epidural abscess, and meningitis, due to Salmonella enterica serotype Enteritidis. This case suggests that Salmonella should be considered as an etiologic pathogen in adult patients with perivertebral infection or meningitis.

Immune Response of Salmonella Challenged Broiler Chickens Fed Diets Containing Gallipro®, a Bacillus subtilis Probiotic

This study was conducted to investigate the effect of feeding a probiotic, Bacillus subtilis, on antibody titers against Newcastle and infectious bursal viruses in broiler chickens challenged with Salmonella enterica serotype Enteritidis. One hundred and sixty 1-day-old broiler chicks were randomly assigned to four treatments in a completely randomized design. The treatments were negative control, probiotic-treated group, challenged group, and challenged probiotic treated group. Salmonella challenging decreased (P < 0.05) the relative weights of spleen and bursa. Inclusion of probiotic to diet of challenged chickens increased the relative weight of spleen, but had no effect on the relative weight of bursa. There were no differences for the antibody titers of chickens between negative control and probiotic-treated group. Salmonella challenging decreased (P < 0.05) antibody titers against Newcastle and infectious bursal viruses. Improvements in the antibody titers were observed by the addition of probiotic to diet of these chickens. The results showed that dietary inclusion of probiotic had no significant effect on immune parameters of chickens at non-contaminated environment, display a greater efficacy at environment contaminated with pathogen and can improve immune responses of infected chickens.

Chicken-Specific Kinome Array Reveals that Salmonella enterica Serovar Enteritidis Modulates Host Immune Signaling Pathways in the Cecum to Establish a Persistence Infection

Non-typhoidal Salmonella enterica induces an early, short-lived pro-inflammatory response in chickens that is asymptomatic of clinical disease and results in a persistent colonization of the gastrointestinal (GI) tract that transmits infections to naïve hosts via fecal shedding of bacteria. The underlying mechanisms that control this persistent colonization of the ceca of chickens by Salmonella are only beginning to be elucidated. We hypothesize that alteration of host signaling pathways mediate the induction of a tolerance response. Using chicken-specific kinomic immune peptide arrays and quantitative RT-PCR of infected cecal tissue, we have previously evaluated the development of disease tolerance in chickens infected with Salmonella enterica serovar Enteritidis (S. Enteritidis) in a persistent infection model (4-14 days post infection). Here, we have further outlined the induction of an tolerance defense strategy in the cecum of chickens infected with S. Enteritidis beginning around four days post-primary infection. The response is characterized by alterations in the activation of T cell signaling mediated by the dephosphorylation of phospholipase c-γ1 (PLCG1) that inhibits NF-κB signaling and activates nuclear factor of activated T-cells (NFAT) signaling and blockage of interferon-γ (IFN-γ) production through the disruption of the JAK-STAT signaling pathway (dephosphorylation of JAK2, JAK3, and STAT4). Further, we measured a significant down-regulation reduction in IFN-γ mRNA expression. These studies, combined with our previous findings, describe global phenotypic changes in the avian cecum of Salmonella Enteritidis-infected chickens that decreases the host responsiveness resulting in the establishment of persistent colonization. The identified tissue protein kinases also represent potential targets for future antimicrobial compounds for decreasing Salmonella loads in the intestines of food animals before going to market.

Functional characterization of glucosamine-6-phosphate synthase (GlmS) in Salmonella enterica serovar Enteritidis

Salmonella is a threat to public health due to consumption of contaminated food. Screening of a transposon library identified a unique mutant that was growth and host cell binding deficient. The objective of this study was to determine the functional role of glucosamine-6-phosphate synthase (GlmS) in the biology and pathogenesis of Salmonella. To examine this, we created a glmS mutant (ΔglmS) of Salmonella and examined the effect on cell envelope integrity, growth, metabolism, and pathogenesis. Our data indicated ΔglmS was defective in growth unless media were supplemented with D-glucosamine (D-GlcN). Examination of the bacterial cell envelope revealed that ΔglmS was highly sensitive to detergents, hydrophobic antibiotics, and bile salts compared to the wild type (WT). A release assay indicated that ΔglmS secreted higher amounts of β-lactamase than the WT in culture supernatant fractions. Furthermore, ΔglmS was attenuated in cell culture models of Salmonella infection. Taken together, this study determined an important role for GlmS in the pathogenesis and biology of Salmonella.

Growth in Egg Yolk Enhances Salmonella Enteritidis Colonization and Virulence in a Mouse Model of Human Colitis

Salmonella Enteritidis (SE) is one of the most common causes of bacterial food-borne illnesses in the world. Despite the SE's ability to colonize and infect a wide-range of host, the most common source of infection continues to be the consumption of contaminated shell eggs and egg-based products. To date, the role of the source of SE infection has not been studied as it relates to SE pathogenesis and resulting disease. Using a streptomycin-treated mouse model of human colitis, this study examined the virulence of SE grown in egg yolk and Luria Bertani (LB) broth, and mouse feces collected from mice experimentally infected with SEE1 (SEE1 passed through mice). Primary observations revealed that the mice infected with SE grown in egg yolk displayed greater illness and disease markers than those infected with SE passed through mice or grown in LB broth. Furthermore, the SE grown in egg yolk achieved higher rates of colonization in the mouse intestines and extra-intestinal organs of infected mice than the SE from LB broth or mouse feces. Our results here indicate that the source of SE infection may contribute to the overall pathogenesis of SE in a second host. These results also suggest that reservoir-pathogen dynamics may be critical for SE's ability to establish colonization and priming for virulence potential.

Inhibition of Salmonella-induced apoptosis as a marker of the protective efficacy of virulence gene-deleted live attenuated vaccine

Vaccination is one of the best protection strategies against Salmonella infection in humans and chickens. Salmonella bacteria must induce apoptosis prior to initiating infection, pathogenesis and evasion of host immune responses. In this study, we evaluated the efficacy of vaccinating chickens against Salmonella Enteritidis (SE) using a vaccine candidate strain (JOL919), constructed by deleting the lon and cpxR genes from a wild-type SE using an allelic exchange method. In present study day old chickens were inoculated with 1×10(7)cfu (colony forming unit) of JOL919 per os. We measured cell-mediated immunity, protective efficacy and extent of apoptosis induction in splenocytes. Seven days post-immunization, the number of CD3+CD4+ and CD3+ CD8+ T cells was significantly higher in the immunized group compared to the control group, indicating a significant augmentation of systemic immune response. The internal organs of chickens immunized with JOL919 had a significantly lower challenge-strain recovery, indicating effective protection and clearance of the challenge strain. Post-challenge, the number of apoptotic cells in the immunized group was significantly lower than in the control group. Additionally, AV/PI (Annexin V/propidium iodide) staining was performed to differentiate between apoptotic cells and necrotic cells, which corroborated TUNEL-assay (terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling) results. The proportions of AV+/PI- and AV+/PI+ cells, which represent the proportions of early apoptotic and late apoptotic/early necrotic cells present, respectively, were significantly lower in the immunized group. Our findings suggest that the apoptotic splenocytes in immunized chickens significantly decreased in number, which occurred concomitantly with a significant rise in systemic immune response and bacterial clearance. This suggests that inhibition of apoptosis may be a marker of protection efficacy in immunized chickens.

Genomic Comparison of the Closely-Related Salmonella enterica Serovars Enteritidis, Dublin and Gallinarum

The Salmonella enterica serovars Enteritidis, Dublin, and Gallinarum are closely related but differ in virulence and host range. To identify the genetic elements responsible for these differences and to better understand how these serovars are evolving, we sequenced the genomes of Enteritidis strain LK5 and Dublin strain SARB12 and compared these genomes to the publicly available Enteritidis P125109, Dublin CT 02021853 and Dublin SD3246 genome sequences. We also compared the publicly available Gallinarum genome sequences from biotype Gallinarum 287/91 and Pullorum RKS5078. Using bioinformatic approaches, we identified single nucleotide polymorphisms, insertions, deletions, and differences in prophage and pseudogene content between strains belonging to the same serovar. Through our analysis we also identified several prophage cargo genes and pseudogenes that affect virulence and may contribute to a host-specific, systemic lifestyle. These results strongly argue that the Enteritidis, Dublin and Gallinarum serovars of Salmonella enterica evolve by acquiring new genes through horizontal gene transfer, followed by the formation of pseudogenes. The loss of genes necessary for a gastrointestinal lifestyle ultimately leads to a systemic lifestyle and niche exclusion in the host-specific serovars.

Membrane cholesterol plays an important role in enteropathogen adhesion and the activation of innate immunity via flagellin-TLR5 signaling

Lipid rafts are cholesterol- and sphingolipid-rich ordered microdomains distributed in the plasma membrane that participates in mammalian signal transduction pathways. To determine the role of lipid rafts in mediating interactions between enteropathogens and intestinal epithelial cells, membrane cholesterol was depleted from Caco-2 and IPEC-J2 cells using methyl-β-cyclodextrin. Cholesterol depletion significantly reduced Escherichia coli and Salmonella enteritidis adhesion and invasion into intestinal epithelial cells. Complementation with exogenous cholesterol restored bacterial adhesion to basal levels. We also evaluated the role of lipid rafts in the activation of Toll-like receptor 5 signaling by bacterial flagellin. Depleting membrane cholesterol reduced the ability of purified recombinant E. coli flagellin to activate TLR5 signaling in intestinal cells. These data suggest that both membrane cholesterol and lipid rafts play important roles in enteropathogen adhesion and contribute to the activation of innate immunity via flagellin-TLR5 signaling.

[Mechanisms of realization of protective effect of miliacin during experimental Salmonella infection: effect of endotoxinemia and cytokine production]

AIM

Evaluate the effect of miliacin on the intensity of endotoxinemia and features of cytokine production in experimental salmonella infection.

MATERIALS AND METHODS

The studies were carried out in 128 male mice (CBAxC57Bl6)F1 divided into 4 groups: I--intact; II--infected; III--infected after administration of miliacin solvent: tween-21; IV--infected after administration of miliacin. Determination of the endotoxin in blood plasma was carried out by using chromogenic LAL-test. Cytokine production was studied in splenocyte culture by EIA method.

RESULTS

Miliacin reduced the intensity of endotoxinemia in mice of group IV. Salmonella infection increased spontaneous (IFNγ) and induced (IL-12, IFNγ, IL-17) cytokine production. Miliacin ensured the most significant increase of spontaneous IL-10, IL-12 and IFNγ production compared with groups II and III. At the same time it limited the increase of induced IL-17 production compared with groups II and III.

CONCLUSION

Protective effect of miliacin is determined by the reduction of endotoxinemia, mobilization of Th-1 response, stimulation of IL-10 production and limitation of IL-17 participation in the development of the inflammatory reaction.

Conjugal transfer of the pathogenicity island ROD21 in Salmonella enterica serovar Enteritidis depends on environmental conditions

Unstable pathogenicity islands are chromosomal elements that can be transferred from one bacterium to another. Salmonella enterica serovar Enteritidis (S. Enteritidis) is a pathogenic bacterium containing such unstable pathogenicity islands. One of them, denominated ROD21, is 26.5 kb in size and capable of excising from the chromosome in certain culture conditions, as well as during bacterial infection of phagocytic cells. In this study we have evaluated whether ROD21 can be effectively transferred from one bacterium to another. We generated a donor and several recipient strains of S. Enteritidis to carry out transfer assays in liquid LB medium. These assays showed that ROD21 is effectively transferred from donor to recipient strains of S. Enteritidis and S. Typhimurium. When Escherichia coli was used as the recipient strain, ROD21 transfer failed to be observed. Subsequently, we showed that a conjugative process was required for the transfer of the island and that changes in temperature and pH increased the transfer frequency between Salmonella strains. Our data indicate that ROD21 is an unstable pathogenicity island that can be transferred by conjugation in a species-specific manner between Salmonellae. Further, ROD21 transfer frequency increases in response to environmental changes, such as pH and temperature.

Role of Type 1 and Type 3 Fimbriae on the Adherence and Pathogenesis ofSalmonella enteritidisin Mice

Through hemagglutination tests two isogenic strains of Salmonella enteritidis were shown to possess type 1 fimbriae (strain V) and type 1 and type 3 fimbriae (strain A). The two strains bound to human buccal and mouse small intestine epithelial cells. Strain A attached to the epithelial cells more readily and in larger numbers in comparison to strain V. Adherence of both strains were sensitive to the presence of D-mannose and pretreatment of the epithelial cells with tannic acid did not promote D-mannose resistant type binding of strain A S. enteritidis to human buccal and mouse small intestine epithelial cells. Furthermore, results from LD50 study indicated that, when the tests were carried out through oral inoculation of the mice the highly fimbriated stain A appeared to be more virulent. However, when the tests were carried out through intraperitoneal inoculation strain V was more virulent. These results indicate that adherence is a major contributing factor to the virulence of S. enteritidis and both type 1 and type 3 fimbriae contribute to this phenomenon.

Effect of plant derived antimicrobials on Salmonella enteritidis adhesion to and invasion of primary chicken oviduct epithelial cells in vitro and virulence gene expression

Salmonella Enteritidis (SE) is a major foodborne pathogen in the United States and one of the most frequently reported Salmonella serotypes globally. Eggs are the most common food product associated with SE infections in humans. The pathogen colonizes the intestinal tract in layers, and migrates to reproductive organs systemically. Since adhesion to and invasion of chicken oviduct epithelial cells (COEC) is critical for SE colonization in reproductive tract, reducing these virulence factors could potentially decrease egg yolk contamination. This study investigated the efficacy of sub-inhibitory concentrations of three plant-derived antimicrobials (PDAs), namely carvacrol, thymol and eugenol in reducing SE adhesion to and invasion of COEC, and survival in chicken macrophages. In addition, the effect of PDAs on SE genes critical for oviduct colonization and macrophage survival was determined using real-time quantitative PCR (RT-qPCR). All PDAs significantly reduced SE adhesion to and invasion of COEC (p < 0.001). The PDAs, except thymol consistently decreased SE survival in macrophages (p < 0.001). RT-qPCR results revealed down-regulation in the expression of genes involved in SE colonization and macrophage survival (p < 0.001). The results indicate that PDAs could potentially be used to control SE colonization in chicken reproductive tract; however, in vivo studies validating these results are warranted.

On the evolutionary history, population genetics and diversity among isolates of Salmonella Enteritidis PFGE pattern JEGX01.0004

Facile laboratory tools are needed to augment identification in contamination events to trace the contamination back to the source (traceback) of Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis). Understanding the evolution and diversity within and among outbreak strains is the first step towards this goal. To this end, we collected 106 new S. Enteriditis isolates within S. Enteriditis Pulsed-Field Gel Electrophoresis (PFGE) pattern JEGX01.0004 and close relatives, and determined their genome sequences. Sources for these isolates spanned food, clinical and environmental farm sources collected during the 2010 S. Enteritidis shell egg outbreak in the United States along with closely related serovars, S. Dublin, S. Gallinarum biovar Pullorum and S. Gallinarum. Despite the highly homogeneous structure of this population, S. Enteritidis isolates examined in this study revealed thousands of SNP differences and numerous variable genes (n = 366). Twenty-one of these genes from the lineages leading to outbreak-associated samples had nonsynonymous (causing amino acid changes) changes and five genes are putatively involved in known Salmonella virulence pathways. While chromosome synteny and genome organization appeared to be stable among these isolates, genome size differences were observed due to variation in the presence or absence of several phages and plasmids, including phage RE-2010, phage P125109, plasmid pSEEE3072_19 (similar to pSENV), plasmid pOU1114 and two newly observed mobile plasmid elements pSEEE1729_15 and pSEEE0956_35. These differences produced modifications to the assembled bases for these draft genomes in the size range of approximately 4.6 to 4.8 mbp, with S. Dublin being larger (∼4.9 mbp) and S. Gallinarum smaller (4.55 mbp) when compared to S. Enteritidis. Finally, we identified variable S. Enteritidis genes associated with virulence pathways that may be useful markers for the development of rapid surveillance and typing methods, potentially aiding in traceback efforts during future outbreaks involving S. Enteritidis PFGE pattern JEGX01.0004.

Characterization of chicken spleen transcriptome after infection with Salmonella enterica serovar Enteritidis

In this study we were interested in identification of new markers of chicken response to Salmonella Enteritidis infection. To reach this aim, gene expression in the spleens of naive chickens and those intravenously infected with S. Enteritidis with or without previous oral vaccination was determined by 454 pyrosequencing of splenic mRNA/cDNA. Forty genes with increased expression at the level of transcription were identified. The most inducible genes encoded avidin (AVD), extracellular fatty acid binding protein (EXFABP), immune responsive gene 1 (IRG1), chemokine ah221 (AH221), trappin-6-like protein (TRAP6) and serum amyloid A (SAA). Using cDNA from sorted splenic B-lymphocytes, macrophages, CD4, CD8 and γδ T-lymphocytes, we found that the above mentioned genes were preferentially expressed in macrophages. AVD, EXFABP, IRG1, AH221, TRAP6 and SAA were induced also in the cecum of chickens orally infected with S. Enteritidis on day 1 of life or day 42 of life. Unusual results were obtained for the immunoglobulin encoding transcripts. Prior to the infection, transcripts coding for the constant parts of IgM, IgY, IgA and Ig light chain were detected in B-lymphocytes. However, after the infection, immunoglobulin encoding transcripts were expressed also by T-lymphocytes and macrophages. Expression of AVD, EXFABP, IRG1, AH221, TRAP6, SAA and all immunoglobulin genes can be therefore used for the characterization of the course of S. Enteritidis infection in chickens.

Survival and virulence of Salmonella enterica serovar enteritidis filaments induced by reduced water activity

Salmonella enterica serovar Enteritidis strain E40 filaments were developed under conditions of a reduced water activity (a(w)) of 0.95 in tryptic soy broth (TSB) or tryptic soy agar (TSA) supplemented with 8% or 7% NaCl, respectively. Filament formation was accompanied by an increase of biomass without an increase in CFU and was affected by incubation temperature and the physical milieu. The greatest amount of filaments was recovered from TSA with 7% NaCl and incubation at 30°C. Within 2 h of transfer to fresh TSB, filaments started to septate into normal-sized cells, resulting in a rapid increase in CFU. S. Enteritidis E40 filaments were not more tolerant of low- or high-temperature stresses than nonfilamented control cells. However, there was greater survival of filaments in 10% bile salts after 24 to 48 h of incubation, during pH 2.0 acid challenge for 10 min, and under desiccation on stainless steel surfaces at 25°C and 75.5% relative humidity for 7 days. S. Enteritidis E40 filaments invaded and multiplied within Caco-2 human intestinal epithelial cells to a similar degree as control cells when a comparable CFU of filaments and control cells was used. S. Enteritidis E40 filaments established a successful infection in mice via intragastric inoculation. The filaments colonized the gastrointestinal tract and disseminated to the spleen and liver at levels comparable to those attained by control cells, even when animals were inoculated with 10- to 100-fold fewer CFU. To our knowledge this is the first demonstration of virulence of stress-induced Salmonella filaments in vitro and in vivo. Formation of filaments by Salmonella in food products and food processing environments is significant to food safety, because detection and quantitation of the pathogen may be compromised. The finding that these filaments are virulent further enhances their potential public health impact.

Epigenetic modification of TLRs in leukocytes is associated with increased susceptibility to Salmonella enteritidis in chickens

Toll-like receptors (TLRs) signaling pathways are the first lines in defense against Salmonella enteritidis (S. enteritidis) infection but the molecular mechanism underlying susceptibility to S. enteritidis infection in chicken remains unclear. SPF chickens injected with S. enteritidis were partitioned into two groups, one consisted of those from Salmonella-susceptible chickens (died within 5 d after injection, n = 6), the other consisted of six Salmonella-resistant chickens that survived for 15 d after injection. The present study shows that the bacterial load in susceptible chickens was significantly higher than that in resistant chickens and TLR4, TLR2-1 and TLR21 expression was strongly diminished in the leukocytes of susceptible chickens compared with those of resistant chickens. The induction of expression of pro-inflammatory cytokine genes, IL-6 and IFN-β, was greatly enhanced in the resistant but not in susceptible chickens. Contrasting with the reduced expression of TLR genes, those of the zinc finger protein 493 (ZNF493) gene and Toll-interacting protein (TOLLIP) gene were enhanced in the susceptible chickens. Finally, the expression of TLR4 in peripheral blood mononuclear cells (PBMCs) infected in vitro with S. enteritidis increased significantly as a result of treatment with 5-Aza-2-deoxycytidine (5-Aza-dc) while either 5-Aza-dc or trichostatin A was effective in up-regulating the expression of TLR21 and TLR2-1. DNA methylation, in the predicted promoter region of TLR4 and TLR21 genes, and an exonic CpG island of the TLR2-1 gene was significantly higher in the susceptible chickens than in resistant chickens. Taken together, the results demonstrate that ZNF493-related epigenetic modification in leukocytes probably accounts for increased susceptibility to S. enteritidis in chickens by diminishing the expression and response of TLR4, TLR21 and TLR2-1.

[The genetic markers of pathogenicity of S. enteritidis, antibiotic resistance of cultures and clinical characteristics of disease]

The article presents the results of evaluation of laboratory diagnostic value of relationships between the rate of detection of fragments of genes of pathogenicity islands associated with E. coli pathogenicity in clinical strains of S. enteritidis, antibiotic resistance of cultures and clinical characteristics of salmonellosis in adults. The sample included 105 patients with salmonellosis to apply the genetic test to isolated strains of S. enteritidis. The E. coli fragments of genes of pathogenicity islands are detected in 102 out of 105 analyzed strains of S. enteritidis (97.1%). The fragments specific to hlyA E. coli are detected in various qualitative and quantitative combinations in 50 (49.0%) clinical strains of S. enteritidis, hlyB--in 54 (52.9%), sfaG--in 57 (55.9%) and sfaA--in 29 (28.4%). The correlation is established between presence of fragments of genes of pathogenicity islands in S.enteritidis associated with E. coli pathogenicity and resistance to ampicillin, doxycycline, cephasoline, chloramphenicol, carbenicillin. The dependence of disease severity from S. enteridis poly-resistance to antibiotics is established.

Salmonella Enteritidis strains from poultry exhibit differential responses to acid stress, oxidative stress, and survival in the egg albumen

Salmonella Enteritidis is the major foodborne pathogen that is primarily transmitted by contaminated chicken meat and eggs. We recently demonstrated that Salmonella Enteritidis strains from poultry differ in their ability to invade human intestinal cells and cause disease in orally challenged mice. Here we hypothesized that the differential virulence of Salmonella Enteritidis strains is due to the differential fitness in the adverse environments that may be encountered during infection in the host. The responses of a panel of six Salmonella Enteritidis strains to acid stress, oxidative stress, survival in egg albumen, and the ability to cause infection in chickens were analyzed. This analysis allowed classification of strains into two categories, stress-sensitive and stress-resistant, with the former showing significantly (p<0.05) reduced survival in acidic (gastric phase of infection) and oxidative (intestinal and systemic phase of infection) stress. Stress-sensitive strains also showed impaired intestinal colonization and systemic dissemination in orally inoculated chickens and failed to survive/grow in egg albumen. Comparative genomic hybridization microarray analysis revealed no differences at the discriminatory level of the whole gene content between stress-sensitive and stress-resistant strains. However, sequencing of rpoS, a stress-regulatory gene, revealed that one of the three stress-sensitive strains carried an insertion mutation in the rpoS resulting in truncation of σ(S). Finding that one of the stress-sensitive strains carried an easily identifiable small polymorphism within a stress-response gene suggests that the other strains may also have small polymorphisms elsewhere in the genome, which likely impact regulation of stress or virulence associated genes in some manner.

Effects of avian triggering receptor expressed on myeloid cells (TREM-A1) activation on heterophil functional activities

A class of innate receptors called the triggering receptors expressed on myeloid cells (TREM) has been discovered and shown to be involved in innate inflammatory responses. The TREM family has been found in the chicken genome and consists of one activating gene (TREM-A1) and two inhibitory genes (TREM-B1 and TREM-B2). However, to date, there have been no reports on the effects of activating the TREM molecules on the functional activity of the primary avian polymorphonuclear cell, the heterophil. To characterize the activation of avian heterophils, we evaluated the effect of receptor ligation on heterophil effector functions. A specific agonistic antibody (Ab) was generated against the peptide sequence of chicken TREM-A1 38-51aa (YNPRQQRWREKSWC). To study TREM-A1 mediated activation, purified peripheral blood heterophils were incubated with various concentrations of the anti-TREM-A1 Ab or control Ab against an irrelevant antigen. Activation via TREM-A1 induces a significant increase in phagocytosis of Salmonella enteritidis, a rapid degranulation, and a dramatic up-regulation in gene expression of the pro-inflammatory cytokine, IL-6, and the inflammatory chemokine, CXCLi2. However, we found no direct TREM-A1 stimulation of the heterophil oxidative burst. Like mammalian TREM, avian TREM-A1 ligation synergizes with the activation of Toll-like receptor-4 (TLR4) ligand, LPS. In addition, the synergistic activity of LPS and TREM-A1 resulted in a significantly (p⩽0.05) increased production of an oxidative burst. Taken together, these results suggest, unlike in mammalian neutrophils, TREM-A1 engagement activates a differential functional activation of avian heterophils, but like mammalian neutrophils, acts in synergy with TLR agonists. These results provide evidence of the function of TREM-A1 in heterophil biology and avian innate immunity.

National outbreak of Salmonella Java phage type 3b variant 9 infection using parallel case-control and case-case study designs, United Kingdom, July to October 2010

Between July and October 2010, a national outbreak comprising 136 cases of Salmonella Java phage type 3b variant 9 was identified by the Health Protection Agency. Most cases were female. Cases had a median age of 39.5 years and lived in London, the South East and East of England. Parallel case–control and case–case study designs were undertaken to test the generated hypotheses. The case–case study aimed to examine if the infection was associated with eating food items purchased from commercial catering settings, and the reference group comprised non-travel related cases of S. Enteritidis infected during the same time period as the cases. The case–control study was designed to examine if the infection was associated with specific food items purchased from commercial catering settings, and recruited case-nominated controls. However, in response to poor recruitment we adapted our methods to investigate food exposures in the same way. Results of epidemiological investigations are compatible with salad vegetables as the potential source, but no common suppliers of salad were identified and no organisms were isolated from environmental and food samples. Limitations in the case–control study highlight the potential value of using a combination of epidemiological methods to investigate outbreaks.

Butyrate enhances disease resistance of chickens by inducing antimicrobial host defense peptide gene expression

Host defense peptides (HDPs) constitute a large group of natural broad-spectrum antimicrobials and an important first line of immunity in virtually all forms of life. Specific augmentation of synthesis of endogenous HDPs may represent a promising antibiotic-alternative approach to disease control. In this study, we tested the hypothesis that exogenous administration of butyrate, a major type of short-chain fatty acids derived from bacterial fermentation of undigested dietary fiber, is capable of inducing HDPs and enhancing disease resistance in chickens. We have found that butyrate is a potent inducer of several, but not all, chicken HDPs in HD11 macrophages as well as in primary monocytes, bone marrow cells, and jejuna and cecal explants. In addition, butyrate treatment enhanced the antibacterial activity of chicken monocytes against Salmonella enteritidis, with a minimum impact on inflammatory cytokine production, phagocytosis, and oxidative burst capacities of the cells. Furthermore, feed supplementation with 0.1% butyrate led to a significant increase in HDP gene expression in the intestinal tract of chickens. More importantly, such a feeding strategy resulted in a nearly 10-fold reduction in the bacterial titer in the cecum following experimental infections with S. enteritidis. Collectively, the results indicated that butyrate-induced synthesis of endogenous HDPs is a phylogenetically conserved mechanism of innate host defense shared by mammals and aves, and that dietary supplementation of butyrate has potential for further development as a convenient antibiotic-alternative strategy to enhance host innate immunity and disease resistance.

[Construction and characterization of an ompR gene deletion mutant from Salmonella enteritidis]

OBJECTIVE

To investigate the role of ompR gene from Salmonella enteritidis in biofilm formation and virulence.

METHODS

We constructed an ompR mutant of Salmonella enteritidis by suicide plasmid pGMB151. Biofilm forming ability of the mutant was detected by crystal violet assay and scanning electron micrography. Virulence of the mutant was determined by assay of adherence to and invasion of epithelial cells, and mouse challenge experiments.

RESULTS

The ompR mutant was confirmed by RT-PCR and the pattern of outer membrane protein. The mutant did not produce cellulose, curli, and biofilm, and showed similar adherence percentage to and invasion percentage of epithelial cells as wild type strain. In addition, intraperitoneal challenge of bacteria in BALB/c mice revealed that LD50 of the mutant strain was 10(6.67) CFU, while that of the wild type strain was less than 2 CFU.

CONCLUSION

These data indicate that the ompR gene is involved in both biofilm formation and virulence in Salmonella enteritidis.

Effects of orally administered Bdellovibrio bacteriovorus on the well-being and Salmonella colonization of young chicks

Bdellovibrio bacteriovorus is a bacterium which preys upon and kills Gram-negative bacteria, including the zoonotic pathogens Escherichia coli and Salmonella. Bdellovibrio has potential as a biocontrol agent, but no reports of it being tested in living animals have been published, and no data on whether Bdellovibrio might spread between animals are available. In this study, we tried to fill this knowledge gap, using B. bacteriovorus HD100 doses in poultry with a normal gut microbiota or predosed with a colonizing Salmonella strain. In both cases, Bdellovibrio was dosed orally along with antacids. After dosing non-Salmonella-infected birds with Bdellovibrio, we measured the health and well-being of the birds and any changes in their gut pathology and culturable microbiota, finding that although a Bdellovibrio dose at 2 days of age altered the overall diversity of the natural gut microbiota in 28-day-old birds, there were no adverse effects on their growth and well-being. Drinking water and fecal matter from the pens in which the birds were housed as groups showed no contamination by Bdellovibrio after dosing. Predatory Bdellovibrio orally administered to birds that had been predosed with a gut-colonizing Salmonella enterica serovar Enteritidis phage type 4 strain (an important zoonotic pathogen) significantly reduced Salmonella numbers in bird gut cecal contents and reduced abnormal cecal morphology, indicating reduced cecal inflammation, compared to the ceca of the untreated controls or a nonpredatory ΔpilA strain, suggesting that these effects were due to predatory action. This work is a first step to applying Bdellovibrio therapeutically for other animal, and possibly human, infections.

The population of a high-virulence strain of Salmonella enterica serovar Enteritidis in subcutaneously infected partridge: a quantitative time-course study using real-time PCR

This research was undertaken to determine the population of a high-virulence strain of Salmonella enterica serovar Enteritidis in partridge by a fluorescent quencher PCR assay and to correlate these findings with the results obtained from the immunohistochemical localization and histopathological examinations of selected Salmonella enterica serovar Enteritidis-infected tissues. To make the results meaningful, a side-by-side bacteriology method (indirect immuno-fluorescent antibody staining) was performed too. The results of indirect immuno-fluorescent antibody staining and immunohistochemical localization were similar to the fluorescent quencher PCR assay. The time course of the appearance of bacterial antigens and tissue lesions in various tissues was coincident with the levels of the bacterial DNA loads at the infection sites. This suggests that Salmonella enterica serovar Enteritidis loads in internal organs are closely correlated with the progression of the infection.

Suppurative thyroiditis caused by Salmonella enteritidis

Bacterial thyroiditis is a rare disease, and one of which the clinical symptoms and signs are frequently misleading. On the other hand, prompt diagnosis is crucial for successful treatment. We report the case of an 82 year-old man with diabetes mellitus type 2 and a history of steroid treatment who presented with severe odynophagia and dysphagia associated with fever, chills, sore throat and right ear pain. Based on the clinical picture, radiological studies, thyroid cytology, blood and thyroid aspirate culture, suppurative thyroiditis caused by Salmonella enteritidis was diagnosed. The patient was successfully treated with antibiotics and surgical drainage.

The renal cyst infection caused by Salmonella enteritidis in a patient with autosomal dominant polycystic kidney disease: how did this pathogen come into the renal cysts?

A 40-year-old Japanese man was admitted to our hospital for investigation of fever and right flank pain starting after watery diarrhea. Salmonella enteritidis was cultured from samples of stool and blood. Although his diarrhea subsided soon, high fever persisted and flank pain got worse. Magnetic resonance imaging (MRI) revealed four areas of abnormal intensity in renal cysts and computed tomography showed the same findings. Renal cysts infection was diagnosed. After ultrasound-guided aspiration of these cysts, his fever subsided. Culture of each aspirate grew Salmonella enteritidis. Although the route of cyst infection in ADPKD generally remains unclear, the clinical course of our patient may indicate that gastrointestinal tract infection progressed to renal cyst infection when bacteremia occurred due to bacterial translocation.

Effect of type 1 fimbriae of Salmonella enterica serotype Enteritidis on bacteraemia and reproductive tract infection in laying hens

Research on the role of type 1 fimbriae of Salmonella enterica serotype Enteritidis in poultry to date has been focused on the intestinal phase of the infection. This study aimed to investigate the role of type 1 fimbriae in a systemic infection by intravenously inoculating chickens with a fimD mutant or its parent strain. The fimD mutant was present in the blood for 3 weeks after infection, while the wild type parent strain was cleared within the first 3 days. The fimD mutant was isolated at least as much as the parent strain from the liver and spleen for up to 3 weeks after inoculation. The wild type strain was cleared from the caeca in the second week, while the fimD mutant was isolated from the caeca for up to 3 weeks after infection. The ovaries were more heavily infected by the fimD mutant than by the wild-type strain. In the first and second week after inoculation, the oviducts were more frequently infected by the mutant strain. The eggs of birds infected with the fimD mutant were less frequently contaminated with Salmonella. The shells of the eggs were more frequently contaminated by the wild type strain than with the mutant strain. Thus, the absence of type 1 fimbriae prolongs bacteraemia, modifies reproductive tract infection and reduces egg shell contamination by Salmonella enterica serovar Enteritidis.

Effects of Salmonella on spatial-temporal processes of jejunal development in chickens

To study effects of Salmonella enteritidis on morphological and functional changes in chicken jejunal development, we analysed gene expression profiles at seven points post-infection in 1-21 day-old broiler chickens. Nine clusters with different gene expression patterns were identified, and the genes in each cluster were further analyzed by a functional annotation clustering method (DAVID). Functional and morphological developmental processes dominated in all the nine clusters. Salmonella infection caused delays in several intestinal-morphological processes, whereas functional metabolic processes occurred in a similar spatial-temporal frame compared to normal jejunum development. A clear difference between normal developing- and Salmonella disturbed jejunum was the higher expression of genes involved in cell turn-over at early stages in the infected jejunum. Surprisingly, we found no clustered immune related processes in the infected birds. To compare the immunological processes between control and Salmonella infected chickens, the gene expression data was superimposed on known immunological KEGG pathways. Furthermore an in-depth analysis on the immune gene level was performed. As expected, we did find immunological processes in the Salmonella infected jejunum. Several of these processes could be verified by immunohistochemistry measurements of different immunological cell types. However, the well-ordered spatial-temporal development of the immune system, as observed in control non-infected animals, was completely abolished in the infected animals. Several immunological processes started much earlier in time, whereas other processes are disorganised. These data indicate that normal morphological and immunological development of jejunum is changed dramatically by a disturbance due to Salmonella infection. Due to the disturbance, the well-organized spatial-temporal development of morphological processes are delayed, those of the immunological development are scattered, whereas metabolic functional processes are almost not affected. This demonstrates the flexibility of developmental processes in the broiler chicken intestine.

[Genetic mechanisms of Salmonella enteritidis biodiversity and clinical features of salmonellosis]

AIM

To assess prevalence of fragments of Escherichia coli pathogenicity islands in Salmonella enteritidis strains as well as to study clinical signs of disease caused by these strains in adults.

MATERIALS AND METHODS

Ninety-six patients with salmonellosis were studied. Ninety strains of S. enteritidis were isolated and tested by PCR for the presence of genes associated with pathogenicity islands of E. coli: hlyA, hlyB, sfaG, and sfaA.

RESULTS

It was determined that DNA fragments homologous to pathogenicity islands of E. coli were present in 87 (96.7%) of S. enteritidis clinical isolates. Disease caused by Salmonella strains which possess only sfaG was mostly mild--7 (33.3%), whereas strains which had sfaG with fragments of hlyA and/or hlyB caused severe disease--7 (50%). sfaA fragments were found mostly in combination with other genes. In such cases the disease was mostly severe--6 (42.8%).

CONCLUSION

Correlation between presence of E. coli pathogenicity islands in Salmonella spp., their antibiotic resistance and severity of infection was established.

Flagellin expression enhances Salmonella accumulation in TLR5-positive macrophages

Recently, it has been reported that Salmonella secrete flagellin in response to host produced lysophospholipids. However, this monomer of the bacterial flagella activates Toll-like receptor 5 (TLR5) in the innate immune system. The objective of this study was to examine the role of flagellin expression during infection of species-specific macrophages (MPhi) which either expressed or lacked TLR5. Initially, TLR5-activity was confirmed in bovine MPhi using Salmonella typhimurium derived-flagellin. Within these cells, recombinant FliC induced a potent CXCL8 response when compared to the heterogeneous (FliC/FljB) form of purified flagellin. Furthermore, neither form of flagellin induced nitrite secretion which was subsequently detected after exposing bovine MPhi to LPS in the presence of IFN-gamma. Flagellin enhanced the accumulation of Salmonella enteritidis in TLR5-positive bovine and human MPhi which was independent of adhesion in bovine MPhi. In contrast, murine MPhis which lacked TLR5 were equally susceptible to hosting S. enteritidis, with or without flagellin. However, lack of flagellin in S. typhimurium marginally inhibited bacterial accumulation in bovine MPhi, where FljB and FliC compensated for the lack of each other. This study suggests that flagellin may be inducing TLR5-dependent internalisation mechanisms in Mcapital EF, Cyrillic which vary qualitatively between different species and Salmonella serotypes.