Molecular characterization and environmental impact of newly isolated lytic phage SLAM_phiST1N3 in the Cornellvirus genus for biocontrol of a multidrug-resistant Salmonella Typhimurium in the swine industry chain.

Salmonella Typhimurium is a highly lethal pathogenic bacterium in weaned piglets, causing significant treatment costs and economic losses in the swine industry. Additionally, due to its ability to induce zoonotic diseases, resulting in harm to humans through the transmission of the pathogen from pork, it presents a serious public health issue. Bacteriophages (phages), viruses that infect specific bacterial strains, have been proposed as an alternative to antibiotics for controlling pathogenic bacteria. In this study, we isolated SLAM_phiST1N3, a phage infecting a multidrug-resistant (MDR) S. Typhimurium wild-type strain isolated from diseased pigs. First, comparative genomics and phylogenetic analysis revealed that SLAM_phiST1N3 belongs to the Cornellvirus genus. Moreover, utilizing a novel classification approach introduced in this study, SLAM_phiST1N3 was classified at the species level. Host range experiments demonstrated that SLAM_phiST1N3 did not infect other pathogenic bacteria or probiotics derived from pigs or other livestock. While complete eradication of Salmonella was not achievable in the liquid inhibition assay, surprisingly, we succeeded in largely eliminating Salmonella in the FIMM analysis, a gut simulation system using weaned piglet feces. Furthermore, using the C. elegans model, we showcased the potential of SLAM_phiST1N3 to prevent S. Typhimurium infection in living organisms. In addition, it was confirmed that bacterial control could be achieved when phage was applied to Salmonella-contaminated pork. pH and temperature stability experiments demonstrated that SLAM_phiST1N3 can endure swine industry processes and digestive conditions. In conclusion, SLAM_phiST1N3 demonstrates potential environmental impact as a substance for Salmonella prevention across various aspects of the swine industry chain.

Evaluation of the in vitro and in vivo efficiency of in-feed bacteriophage cocktail application to control Salmonella Typhimurium and Salmonella Enteritidis infection in broiler chicks.

RESEARCH HIGHLIGHTS: Bacteriophage (BP) cocktail was partially resistant to different temperatures and pH values.The BP cocktail showed lytic effects on different Salmonella isolates.The BP cocktail reduced Salmonella colonization in the internal organs of broilers.

Effects of in ovo injection of bacterial peptides and CpG-ODN on Salmonella enterica serovar Heidelberg infection in specific pathogen-free (SPF) chicks.

RESEARCH HIGHLIGHTS: Peptides + CpG-ODN reduced SH in caeca at the first week post-infection.Administered formulations did not reduce SH-faecal excretion.Levels of intestinal IgA were similar between all groups.CpG-ODN improved some parameters associated with chick intestinal health.

Commercial vaccine provides cross-protection by reducing colonization of Salmonella enterica serovars Infantis and Hadar in turkeys.

Human foodborne outbreaks with antibiotic-resistant Salmonella enterica associated with contaminated poultry products have recently involved serogroup C serovars Infantis and Hadar. The current study evaluated a commercially available Salmonella vaccine for cross-protection against Infantis and Hadar serovars in turkeys. The live, attenuated S. Typhimurium (serogroup B) vaccine significantly reduced colonization of intestinal tissues (cecum, cecal tonsils, and cloaca) by serovars Infantis (C1) and Hadar (C2) and significantly limited systemic dissemination to the spleen. S. Infantis, but not S. Hadar, disseminated to bone marrow in non-vaccinated turkeys, but vaccination prevented S. Infantis dissemination to the bone marrow. The S. Infantis challenge strain contained the pESI megaplasmid, and virulence mechanism(s) residing on this plasmid may support dissemination and/or colonization of systemic niches such as myeloid tissue. Collectively, the data indicate that vaccinating turkeys with the serogroup B S. Typhimurium vaccine limited intestinal colonization and systemic dissemination by serogroup C serovars Infantis and Hadar.

Research Note: Xylooligosaccharide directly attenuates Salmonella Typhimurium colonization and its induction of impairments in intestinal barrier and growth performance of broilers.

Xylooligosaccharide (XOS) is known as a prebiotic, however, it is unknown whether XOS can directly protect against bacterial infection. This study aimed to investigate the direct inhibitory effects of XOS on Salmonella Typhimurium colonization and the inductive impairments in gut health and growth performance in broilers. We first probed the inhibitory effects of XOS on S. Typhimurium adhesion and its induction of intestinal epithelial cell (IPEC-J2) injuries. Afterward, 168 one-day-old yellow-feathered broilers were randomly divided into 3 groups (7 replicates/group): negative control (NC, received a basal diet), positive control (PC, received a basal diet with S. Typhimurium challenge) and XOS group (PC birds + 1,500 mg/kg XOS). All birds except those in NC were orally challenged with S. Typhimurium from 8 to 10 d of age. Parameters were analyzed on d 11. The results showed that XOS inhibited S. Typhimurium adhesion and the inductive injuries of IPEC-J2 cells by lowering (P < 0.05) certain adhesion-related genes expression of this bacterium. It also alleviated S. Typhimurium-induced increase (P < 0.05) in the expression of certain inflammatory cytokines and tight junction (TJ) proteins of IPEC-J2 cells. Supplementing XOS to S. Typhimurium-challenged broilers attenuated the elevations (P < 0.05) in S. Typhimurium colonization of ileal mucosa and its translocation to the liver and spleen, as well as increased (P < 0.05) certain TJ proteins expression of ileum. Besides, XOS addition normalized S. Typhimurium-induced impairments (P < 0.05) in ileal morphology, final body weight and average daily gain in broilers. Collectively, supplemental XOS directly suppressed intestinal colonization of S. Typhimurium by diminishing its adhesiveness and subsequently mitigated destructions in intestinal barriers, thus contributing to weaken growth retardation in challenged broilers. Our findings provide a new insight into the mechanisms of XOS limiting Salmonella infection in chickens.

Strain specificity of lactobacilli with promoted colonization by galactooligosaccharides administration in protecting intestinal barriers during Salmonella infection.

INTRODUCTION: Galactooligosaccharides (GOS) are lactogenic prebiotics that exert health benefits by stimulating the growth of different Lactobacillus strains in the gastrointestinal (GI) tract. OBJECTIVES: This study aimed to investigate the mechanism of action of different GOS-enriched lactobacilli in intestinal health. METHODS: Piglets and mice were supplemented with GOS to identify specific enrichment of Lactobacillus. The protective effects of individual GOS-enriched lactobacilli were investigated in Salmonella-infected mice. Macrophage depletion and transcriptome analysis were further performed to assess the involvement of macrophages and the underlying mechanisms of individual lactobacilli. An in vitro cell co-culture system was also used to evaluate the anti-adhesive and anti-invasive activities of lactobacilli against Salmonella in epithelial cells. RESULTS: GOS markedly increased the relative abundance of three lactobacilli including L. delbrueckii, L. johnsonii, and L. reuteri in both piglets and mice. Supplementation with GOS further alleviated Salmonella infection in mice. L. delbrueckii (ATCC®BAA 365™), but not L. johnsonii or L. reuteri, enhanced propionate production in the intestinal tract and ameliorated Salmonella-induced intestinal inflammation and barrier dysfunction by suppressing the JAK2-STAT3 signaling and M1 macrophage polarization. L. johnsonii (BNCC 186110), on the other hand, inhibited Salmonella adhesion and invasion of epithelial cells through competitive exclusion. However, L. reuteri (BNCC 186135) failed to protect mice against Salmonella infection. CONCLUSION: GOS-enriched lactobacilli show a differential role in protecting against Salmonella-induced intestinal barrier dysfunction and inflammation. Our results provide novel insights into the mechanism of action of GOS and individual Lactobacillus strains in the control and prevention of intestinal inflammatory disorders.

Assessment of environmental safety and protective efficacy of O-antigen deficient DIVA capable Salmonella Enteritidis against chicken salmonellosis.

In this study, we incorporated deletion of the O-antigen ligase gene to an attenuated Salmonella Enteritidis (SE) strain, JOL919 (SE PS; Δlon ΔcpxR), using the Lambda-Red recombination method and evaluated the safety and immunological aspects of the novel genotype, JOL2381 (SE VS: Δlon, ΔcpxR, ΔrfaL). Assessment of fecal shedding and organ persistence following administration via oral and IM routes revealed that the SE VS was safer than its parent strain, SE PS. Immunological assays confirmed that immunization via the oral route with SE PS was superior to the SE VS. However, chickens immunized with SE PS and SE VS strains via the IM route showed higher humoral and cell-mediated immune responses. Compared to PBS control, the IM route of immunization with SE VS resulted in a higher IgY antibody titer and expansion of CD4+ and CD8+ T-cell populations, which resulted in the clearance of Salmonella from the liver and splenic tissues. Furthermore, deletion of the O-antigen ligase gene caused lower production of LPS-specific antibodies in the host, promoting DIVA functionality and making it a plausible candidate for field utilization. Due to significant protection, high attenuation, and environmental safety concerns, the present SE VS strain is an ideal choice to prevent chicken salmonellosis and ensure public health.

Salmonella typhimurium targeting with monoclonal antibodies prevents infection in mice.

Salmonella is a prevalent foodborne and waterborne pathogens threating global public health and food safety. Given the diversity of Salmonella serotypes and the emergence of antibiotic-resistant strains, there is an urgent need for the development of broadly protective therapies. This study aims to prepare monoclonal antibodies (Mabs) with broad reactivity against multi-serotype Salmonella strains, potentially offering cross-protection. We prepared two Mabs F1D4 and B7D4 against protein FliK and BcsZ, two potential vaccine candidates against multi-serotype Salmonella. The two Mabs belonging to IgG1 isotype exhibited high titers of 1:256,000 and 1:512,000 respectively, as well as broad cross-reactivity against 28 different serotypes of Salmonella strains with percentages of 89.29% and 92.86%, correspondingly. Neutralizing effects of the two Mabs on Salmonella growth, adhesion, invasion and motility was evaluated in vitro using bacteriostatic and bactericidal activity with and without complement and bacterial invasion inhibition assay. Additionally, cytotoxicity assays, animal toxicity analyses, and pharmacokinetic evaluations demonstrated the safety and sustained effectiveness of both Mabs. Furthermore, F1D4 or B7D4-therapy in mice challenged with S. Typhimurium LT2 exhibited milder organs damage and lower Salmonella colonization, as well as the higher relative survival of 86.67% and 93.33% respectively. This study produced two broadly reactive and potential cross protective Mabs F1D4 and B7D4, which offered new possibilities for immunotherapy of salmonellosis.

Comparison of yeast-derived commercial feed additives on Salmonella Enteritidis survival and microbiota populations in rooster cecal in vitro incubations.

Yeast-derived products have become more of an interest in the poultry industry as of late because of their use in modulating the gastrointestinal tract (GIT) microbiome to both improve production parameters and prevent infection. This study aimed to evaluate the effects of various yeast-derived products on Salmonella enterica inoculation in un in vitro rooster cecal incubations and associated effects on the cecal microbiome. Cecal contents were obtained from 53-wk old White Leghorn H & N Nick Chick roosters (n = 3) fed a wheat-based, commercial-type basal diet. Cecal contents were diluted 1:3000 in anaerobic dilution solution (ADS) in an anaerobic chamber, with 20 mL aliquoted to each serum bottle. There were three controls (n = 3): basal diet only, diluted cecal contents only, and basal diet and diluted cecal contents; and five treatments containing the basal diet and diluted cecal contents (n = 3): Citristim® (ADM), ImmunoWall® (ICC), Maxi-Gen Plus® (CBS Bio Platforms), Hilyses® (ICC), and Original XPC® (Diamond V). All treatments were applied at a rate of 2.5 kg/tonne or less. All groups were inoculated with a nalidixic acid-resistant strain of Salmonella Enteritidis at 10^7 CFU/mL and incubated at 37 deg C. Samples were collected at 0, 24, and 48 h for S. Enteritidis enumeration and 16S rDNA microbial sequencing. Salmonella data were log-transformed and analyzed in a two-way ANOVA with means separated using Tukey's HSD (P≤0.05). Genomic DNA was extracted, and resulting libraries were prepared and sequenced using an Illumina MiSeq. Sequencing data were analyzed in QIIME2 (2021.4) with diversity metrics (alpha and beta), and an analysis of the composition of microbiomes (ANCOM) was performed. Main effects were considered significant at P≤0.05, with pairwise differences considered significant at Q≤0.05. There was an interaction of treatment and time on the enumeration of Salmonella where treatments of Citristim, Immunowall, Hilyses, and XPC reduced Salmonella by 1 log CFU/mL compared to the controls. At 48 h, each yeast product treatment reduced Salmonella by 3 log CFU/mL compared to the controls. There was no main effect of treatment on the alpha diversity metrics, richness, or evenness (P > 0.05). Treatment affected the beta diversity, abundance, and phylogenetic differences, but there were no pairwise differences (P>0.05, Q>0.05). Using ANCOM at the genus level, the taxa Synergistes, Alloprevotella, Sutterella, and Megasphaera abundance were significantly different (W = 154,147,145,140, respectively). These results demonstrate the potential of these yeast-derived products to reduce foodborne pathogens, such as Salmonella Enteriditis, in vitro, without negatively disrupting the cecal microbiome.

Metabolomic and microbiome analysis of the protective effects of Puerarin against Salmonella Enteritidis Infection in chicks.

BACKGROUND: Salmonella Enteritidis is a zoonotic pathogen and poses a substantial risk to human health, as well as significant financial losses to the livestock and poultry industries. It is currently urgent to identify alternatives to antibiotic treatment. RESULTS: In this study, we explored the influence of Puerarin on the immunological response, intestinal flora, serum metabolome, and growth performance of chicks infected with Salmonella Enteritidis. Chicks were weighed at specific time points and the average daily gain (ADG) was calculated. Serum, intestinal, and cecal content samples were collected on days 10 and 17. The results showed that 100 mg/kg of Puerarin significantly suppressed inflammation and enhanced immune function. Metabolomic analysis showed significant differences in serum metabolites after Puerarin treatment and suggested that Puerarin may regulate abnormal amino acid and lipid metabolism after Salmonella Enteritidis infection through the autophagic and ABC transporter pathways. In addition, Puerarin suppressed Salmonella Enteritidis-induced intestinal flora dysbiosis through modulation of the microbial community structures (increased Lactobacillus, Faecalibacterium, and Subdoligranulum), as demonstrated by 16S rRNA analysis. CONCLUSIONS: In conclusion, Puerarin can improve growth performance in chicks, suppress the inflammatory response in vivo, enhance immunity, and regulate lipid and amino acid metabolism and the intestinal flora.

The Importance of Hazard Analysis by Critical Control Point for Effective Pathogen Control in Animal Feed: Assessment of Salmonella Control in Feed Production in Sweden, 1982-2005.

This study is the first to show that Hazard Analysis by Critical Control Point (HACCP)-based monitoring can be an effective tool for ensuring Salmonella-safe feed, by virtually eliminating feedborne Salmonella infection even in broiler production. Data from the control of Salmonella in feed and food animal production during 1982-2005, showed that conventional endpoint testing in feed mills did not ensure a Salmonella-safe feed, and in one feed mill failed to detect Salmonella contamination, resulting in the feed infecting 80 out of 197 (40.6%) recipient broiler flocks. Following implementation in 1991 of a HACCP-based control in feed mills, the annual number of samples tested at specified critical control points during a 15-year period increased from ∼4400 to 10,000, while the proportion of Salmonella-contaminated samples decreased from 2.0% to 0.3%. Thus, introduction of HACCP was followed by a dramatic decrease, from 40 to <5, in the annual number of Salmonella-infected broiler flocks identified by preslaughter monitoring. Incidence has generally remained at that low level, despite production since 1980 increasing from 39 to 112 million chickens per year. Feed mills start using soymeal with an unsafe Salmonella status and possibly with a suboptimal HACCP control, increased their level of Salmonella-contaminated HACCP samples, and their feed subsequently infected 78 swine-producing herds. The results also show that the HACCP concept can be an effective tool to supply feed mills with Salmonella-safe feed ingredients as demonstrated for a soybean crushing plant, which produced Salmonella-safe soymeal over a 19-year period despite frequent (34%) and highly varied (92 different serovars) Salmonella contamination in samples from incoming soybean. Similar results are reported for a plant producing rapeseed meal. It is emphasized that the achievements described through use of the HACCP required interventions of relevant preventive biosecurity measures and corrective actions when the HACCP-based monitoring identified Salmonella contamination.

Research Note: The effects of a Lactobacillus helveticus ATCC 15009-derived postbiotic mitigating Salmonella Gallinarum colonization in commercial layer chicks.

This study aimed to assess the effects of a Lactobacillus helveticus ATCC 15009-derived postbiotic in mitigating experimental Salmonella Gallinarum infection. For this purpose, a sample of Lactobacillus sp. was inoculated in 2 different media, each containing different postbiotics (sensitized and nonsensitized). Both inocula had their antagonistic effect over S. Gallinarum tested through the spot-on-the-lawn method. It revealed that the sensitized postbiotic had a higher action potential over Lactobacillus sp. than the nonsensitized one (P < 0.05). Then, 48 day of hatch chicks were divided into 4 groups: A = Lactobacillus sp. (109 CFU/mL) inoculum on the 18th day; B = Lactobacillus sp. (109 CFU/mL) inoculum on the 18th day and postbiotic inoculum on the 19th day; C = postbiotic inoculum on the 19th day; and D = sterile saline inoculum on 18th and 19th days. On the 21st day, all chicks were infected with S. Gallinarum (109 CFU/mL). On the 23rd day, the animals were euthanized by cervical dislocation, and the ceca and liver were aseptically removed. Bacterial count of S. Gallinarum with serial decimal dilution was performed with these organs. It revealed that the prophylactic treatment with the postbiotic that modulates the intestinal microbiota was as efficient as the probiotic administration in reducing S. Gallinarum in the cecum and liver of chicks (P < 0.05). These data point to a new range of alternatives for preventing S. Gallinarum, which might help the poultry industry produce safer food for human consumption.

Controlling Salmonella: strategies for feed, the farm, and the processing plant.

Controlling Salmonella in poultry is an ongoing food safety measure and while significant progress has been made, there is a need to continue to evaluate different strategies that include understanding Salmonella-poultry interaction, Salmonella-microbiota interactions, Salmonella genetics and response to adverse conditions, and preharvest and postharvest parameters that enable persistence. The purpose of this symposium is to discuss different strategies to consider from feed milling to the farm to the processing environment. This Poultry Science Association symposium paper is divided into 5 different sections that covers 1) immunological aspects of Salmonella control, 2) application of Salmonella genetics for targeted control strategies in poultry production, 3) improving poultry feed hygienics: utilizing feed manufacture techniques and equipment to improve feed hygienics, 4) practical on farm interventions for controlling Salmonella-what works and what may not work, and 5) monitoring and mitigating Salmonella in poultry. These topics elucidate the critical need to establish control strategies that will improve poultry gut health and limit conditions that exposes Salmonella to stress causing alterations to virulence and pathogenicity both at preharvest and postharvest poultry production. This information is relevant to the poultry industry's continued efforts to ensure food safety poultry production.

Nigella sativa-chitosan nanoparticles: Novel intestinal mucosal immunomodulator controls and protects against Salmonella enterica serovar Enteritidis infection in broilers.

BACKGROUND: Salmonella Enteritidis (SE) propagates in chickens' gastrointestinal surfaces and is transmitted to humans, causing food poisoning. Oral supplementation with natural nanoparticles can overcome the harsh gastrointestinal conditions facing oral vaccines and requires no antibiotic administration to protect against microbial infection. This study was designed to study Nigella sativa-chitosan nanoparticles (CNP-NS) prophylactic immunomodulatory efficacy against SE infection in broiler chicks. The CNP-NS was prepared and characterized, and its in vivo immunomodulatory activities against an avian virulent-MDR SE-induced challenge in chicks were investigated. RESULT: To verify the immune-protective activities of the CNP-NS, colony forming units (CFU) in the liver and fecal droppings; intestinal histopathological alterations and immune cell recruitment; MUC-2, TLR-4, cecal cytokines, and specific IgA gene expression levels were assessed. On the 7th and 12th days after the SE challenge, the CNP-NS supplemented chicks showed complete clearance of SE CFU in livers and fecal droppings, as well as an improvement in food conversion rate compared to non-supplemented CNP-NS that revealed the presence of the challenge SE CFU on the same days. A prominent influx of antigen presenting cells and lymphoid aggregates into the intestinal wall, spleen, and liver was detected with improvements in the intestinal villi morphometry of the CNP-NS-supplemented chicks. The changes of INF-γ, IL-1ß, and IL-4 cecal cytokines, as well as TLR-4, MUC-2, and IgA mRNA expression levels, confirm CNP-NS immunomodulatory activities and provide a mechanism(s) for its protective actions against the induced SE challenge of the tested chickens. CONCLUSION: These findings suggest promising useful insights into CNP-NS supplementation as a safe food additive for poultry meat consumers' and a protective immunomodulator of the chickens' mucosal immune systems. It could be recommended for epidemiological purposes to reduce the risk of SE food poisoning and transmission to humans.

"EvoVax" - A rationally designed inactivated Salmonella Typhimurium vaccine induces strong and long-lasting immune responses in pigs.

Salmonella enterica subspecies enterica serovar Typhimurium (S.Tm) poses a considerable threat to public health due to its zoonotic potential. Human infections are mostly foodborne, and pork and pork products are ranked among the top culprits for transmission. In addition, the high percentage of antibiotic resistance, especially in monophasic S.Tm, limits treatment options when needed. Better S.Tm control would therefore be of benefit both for farm animals and for safety of the human food chain. A promising pre-harvest intervention is vaccination. In this study we tested safety and immunogenicity of an oral inactivated S.Tm vaccine, which has been recently shown to generate an "evolutionary trap" and to massively reduce S.Tm colonization and transmission in mice. We show that this vaccine is highly immunogenic and safe in post-weaning pigs and that administration of a single oral dose results in a strong and long-lasting serum IgG response. This has several advantages over existing - mainly live - vaccines against S.Tm, both in improved seroconversion and reduced risk of vaccine-strain persistence and reversion to virulence.

Assessing pig farm biosecurity measures for the control of Salmonella on European farms.

Salmonella spp. is a common zoonotic pathogen, causing gastrointestinal infections in people. Pigs and pig meat are a major source of infection. Although farm biosecurity is believed to be important for controlling Salmonella transmission, robust evidence is lacking on which measures are most effective. This study enrolled 250 pig farms across nine European countries. From each farm, 20 pooled faecal samples (or similar information) were collected and analysed for Salmonella presence. Based on the proportion of positive results, farms were categorised as at higher or lower Salmonella risk, and associations with variables from a comprehensive questionnaire investigated. Multivariable analysis indicated that farms were less likely to be in the higher-risk category if they had '<400 sows'; used rodent baits close to pig enclosures; isolated stay-behind (sick) pigs; did not answer that the hygiene lock/ anteroom was easy to clean; did not have a full perimeter fence; did apply downtime of at least 3 days between farrowing batches; and had fully slatted flooring in all fattener buildings. A principal components analysis assessed the sources of variation between farms, and correlation between variables. The study results suggest simple control measures that could be prioritised on European pig farms to control Salmonella.

Survival persistence of the 3 common Salmonella enterica serotypes isolated from broilers' in different matrices.

Broiler meat is the predominant source of Salmonella as a foodborne pathogen. Several control strategies have focused on the reduction of Salmonella spp. levels at different production stages. However, the persistence of Salmonella between consecutive flocks is still of great concern. This study was designed to understand the cause of reinfection in broiler flocks due to survival of Salmonella in feeding lines of related matrices. Salmonella (S.) Enteritidis, S. Infantis, and S. Typhimurium isolated from broiler farms in North-West Germany were used. Four types of matrices (phosphate buffer saline (PBS), dietary plant fat, fat with feed mixture, and feed) were applied to evaluate Salmonella survival (with the initial dose about 8.0 log10 CFU/mL) during a simulation of 4 production cycles. To evaluate the growth and survival status of Salmonella ISO 6579-1:2017 were performed (quantitatively by plate count method (PCM) and most probable number method (MPN)) and qualitatively) at 5 defined time points (-7, 0, 4, 7, and 35 d). In all matrices and for the 3 serovars, the Salmonella count decreased at the end of the fourth cycle in comparison to the beginning of the experimental infection, and was still cultivated except for fat matrix. The PBS matrices showed the highest survival level of Salmonella and did not decline drastically by the end of the fourth cycle (5.93 ± 0.00, 5.87 ± 0.02, 5.73 ± 0.05 log10 CFU/mL, respectively). However, the fat matrices showed the lowest survival level for the 3 isolates at d 35 since the first cycle (0 log10 CFU/mL using PCM). Regarding the fat-feed mixture, and feed matrices, there was a fluctuation in the survival rate of Salmonella (all serovars) within each cycle. For the qualitative method, the 3 serovars persisted in all matrices until the end of the fourth cycle except for fat matrices. The present study highlights the ability of Salmonella to survive for a long time in different temperatures and matrices despite efficient cleaning and disinfection processes in the feeding lines, which may influence reinfection with Salmonella in poultry houses.

Screening of lipid-A related genes and development of low-endotoxicity live-attenuated Salmonella gallinarum by arnT deletion that elicits immune responses and protection against fowl typhoid in chickens.

In the present study, lipid-A gene mutants of Salmonella gallinarum (SG) were screened, and the arnT mutant exhibited optimal acidic and oxidative-stress and macrophage-survival. Modifying lipid-A by arnT-deletion resulted in significantly reduced endotoxicity, virulence, and mortality. Therefore, the arnT-deleted vaccine-candidate strain JOL2841 was constructed and demonstrated to be safe due to appropriate clearance by the chicken immune system. The reduced-endotoxicity of JOL2841 was evident from the downregulation of TNFα and IL-1ß inflammatory cytokines, no inflammatory signs in organ gross-examination, and histopathological analysis. The IgY and IgA antibody titres, CD4, and CD8 T-cell population improvements, and IL-4, IL-2, and INFγ expression decipher the profound Th2 and Th1 immunogenicity. Consequently, JOL2841 exhibited prominent protection against wild-type SG challenge, as revealed by organ pathogen-load determination, organ gross-examination, and histopathological examination. Overall, the study represented the first report of arnT deficient SG resulted in negligible endotoxicity, low-virulence, safety and coordinated elicitation of humoral and cell-mediated immune response in chickens.

Investigation of a gel-based delivery method for the administration of a live, attenuated Salmonella Typhimurium vaccine.

Poultry vaccines are often administered using water as a suspension media and applied using an oral or coarse spray method. Gel-based vaccine diluents have been developed as an alternative vaccine delivery method. Gels are more viscous, and droplets adhere more effectively to feathers giving the vaccine a longer time to be ingested (through preening). Application of gel diluents with live bacterial vaccines, however, is limited. The present study tested a gel diluent prepared in various media, using a live, attenuated Salmonella Typhimurium vaccine, Vaxsafe ST. Reconstitution in gel diluent did not negatively affect vaccine viability or motility. The invasive capacity of vaccine suspended in gel diluent into cultured intestinal epithelial cells was also tested. Results demonstrated that vaccine suspended in gel diluent retained invasiveness. Day old chicks were orally administered with Vaxsafe ST suspended in gel diluent to characterize in vivo colonization capacity of the vaccine. The results revealed that the VaxSafe ST suspended in gel diluent could efficiently colonize the caeca of chicks, which is needed for the development of effective immunity.

A systematic review and meta-analysis of the sources of Salmonella in poultry production (pre-harvest) and their relative contributions to the microbial risk of poultry meat.

Salmonella is a major foodborne pathogen associated with poultry and poultry products and a leading cause for human salmonellosis. Salmonella is known to transmit in poultry flocks both vertically and horizontally. However, there is a lack of knowledge on relative contribution of the factors on Salmonella prevalence in poultry live production system including hatchery, feed, water, environment-interior, and -exterior. Therefore, a systematic review and meta-analysis was conducted to quantify the potential sources of Salmonella during preharvest and their relative contributions to the microbial risk of poultry meat. A total of 16,800 studies identified from Google Scholar and 37 relevant studies were included in the meta-analysis for relative contributions to Salmonella positivity on broilers after applying exclusion criteria. A generalized linear mixed model approach combined with logit transformation was used in the current study to stabilize the variance. The analysis revealed that the hatchery is the most significant contributor of Salmonella with a prevalence of 48.5%. Litter, feces, and poultry house internal environment were the other 3 major contributing factors with a prevalence of 25.4, 16.3, and 7.9%, respectively. Moreover, poultry house external environment (4.7%), feed (4.8%), chicks (4.7%), and drinker water also contributed to the Salmonella positivity. Results from this meta-analysis informed the urgent need for controls in live production to further reduce Salmonella in fresh, processed poultry. The control strategies can include eliminating the sources of Salmonella and incorporating interventions in live production to reduce Salmonella concentrations in broilers.