Opinion of the Scientific Panel on biological hazards (BIOHAZ) related to the use of vaccines for the control of Salmonella in poultry

Prebiotic galactooligosaccharide feed modifies the chicken gut microbiota to efficiently clear Salmonella

Chicken meat is contaminated with Salmonella from the gut of infected chickens during slaughter. Eradication of Salmonella from broiler chickens through hygiene measures and/or vaccination is not cost-effective; complementary approaches are required. A mature gut microbiota obstructs Salmonella infection in chickens, and deliberate fortification of colonization resistance through prebiotic feed formulations would benefit public health and poultry production. Prebiotic galactooligosaccharides hastens Salmonella clearance from the gut of infected chickens. To better understand the role of galactooligosaccharides in colonization resistance, broiler chickens were raised on a wheat-soybean meal-based feed, with or without galactooligosaccharides for the first 24 days of life. Chickens were orally challenged with Salmonella enterica serovar Enteritidis at 20 days and the effect of supplementary galactooligosaccharides characterized by profiling Salmonella colonization, gut microbiota, innate immune response, and cecal short-chain fatty acid concentrations. Exposure to dietary galactooligosaccharides shortened the time to clear S. Enteritidis from the ceca. Differential abundance analysis of the cecal microbiota associated Salmonella challenge with a bacterial taxon belonging to the Acidaminococcaceae family (P < 0.005). Increased cecal concentrations of the short-chain fatty acids propionate and valerate were measured in Salmonella-challenged chickens sustained on either control or galactooligosaccharide-supplemented feed relative to mock-challenged controls; but far greater concentrations were detected in chickens fed a galactooligosaccharide-supplemented diet in early life. The abundance of the Acidaminococcaceae taxon exhibited a positive correlation with the cecal concentrations of propionate (ρ = 0.724, P = 0.008) and valerate (ρ = 0.71, P = 0.013). The absence of cecal pro-inflammatory transcriptional responses suggest that the rapid Salmonella clearance observed for the galactooligosaccharide-supplemented diet was not linked to innate immune function.

IMPORTANCE

Work presented here identifies bacterial taxa responsible for colonization resistance to Salmonella in broiler chickens. Deliberate cultivation of these taxa with prebiotic galactooligosaccharide has potential as a straight-forward, safe, and cost-effective intervention against Salmonella. We hypothesize that catabolism of galactooligosaccharide and its breakdown products by indigenous microorganisms colonizing the chicken gut produce excess levels of propionate. In the absence of gross inflammation, propionate is inimical to Salmonella and hastens intestinal clearance.

Dietary Supplementation of Brevibacillus laterosporus S62-9 Improves Broiler Growth and Immunity by Regulating Cecal Microbiota and Metabolites

Brevibacillus laterosporus has been added as a direct-fed microbiota to chicken. Yet, few studies have reported the effects of B. laterosporus on broiler growth and gut microbiota. The aim of this study was to evaluate the effects of B. laterosporus S62-9 on growth performance, immunity, cecal microbiota, and metabolites in broilers. A total of 160 1-day-old broilers were randomly divided into S62-9 and control groups, with or without 106 CFU/g B. laterosporus S62-9 supplementation, respectively. During the 42 days feeding, body weight and feed intake were recorded weekly. Serum was collected for immunoglobulin determination, and cecal contents were taken for 16S rDNA analysis and metabolome at Day 42. Results indicated that the broilers in S62-9 group showed an increase in body weight of 7.2% and 5.19% improvement in feed conversion ratio compared to the control group. The B. laterosporus S62-9 supplementation promoted the maturation of immune organs and increased the concentration of serum immunoglobulins. Furthermore, the α-diversity of cecal microbiota was improved in the S62-9 group. B. laterosporus S62-9 supplementation increased the relative abundance of beneficial bacteria including Akkermansia, Bifidobacterium, and Lactobacillus, while decreased the relative abundance of pathogens including Klebsiella and Pseudomonas. Untargeted metabolomics revealed that 53 differential metabolites between the two groups. The differential metabolites were enriched in 4 amino acid metabolic pathways, including arginine biosynthesis and glutathione metabolism. In summary, B. laterosporus S62-9 supplementation could improve the growth performance and immunity through the regulation of gut microbiota and metabolome in broilers.

Mitigation Potential of Herbal Extracts and Constituent Bioactive Compounds on Salmonella in Meat-Type Poultry

Herbal extracts have been widely evaluated in poultry production for their beneficial effects and potential substitute for antibiotics, which contribute to AMR and risks to human health through the consumption of infected meat. Salmonellosis is a systemic infection caused by Salmonella, an intracellular bacterium with the ability to cause systemic infections with significant implications for both the health and safety of farmers and consumers. The excessive use of antibiotics has escalated the incidence of antibiotic resistance bacteria in the poultry and livestock industry, highlighting the urgent need for alternatives especially in meat-type poultry. Both in vivo usage and in vitro studies of bioactive compounds from herbal extracts have demonstrated the effective antimicrobial activities against pathogenic bacteria, showing promise in managing Salmonella infections and enhancing poultry performance. Phytobiotic feed additives have shown promising results in improving poultry output due to their pharmacological properties, such as stimulating consumption, and enhancing antioxidant properties and preventing the increasing antimicrobial resistance threats. Despite potential for synergistic effects from plant-derived compounds, a further investigation into is essential to fully understand their role and mechanisms of action, for developing effective delivery systems, and for assessing environmental sustainability in controlling Salmonella in poultry production.

Salmonella spp. in poultry production-A review of the role of interventions along the production continuum

Salmonella is a significant pathogen of human and animal health and poultry are one of the most common sources linked with foodborne illness worldwide. Global production of poultry meat and products has increased significantly over the last decade or more as a result of consumer demand and the changing demographics of the world's population, where poultry meat forms a greater part of the diet. In addition, the relatively fast growth rate of birds which is significantly higher than other meat species also plays a role in how poultry production has intensified. In an effort to meet the greater demand for poultry meat and products, modern poultry production and processing practices have changed and practices to target control and reduction of foodborne pathogens such as Salmonella have been implemented. These strategies are implemented along the continuum from parent and grandparent flocks to breeders, the farm and finished broilers to transport and processing and finally from retail to the consumer. This review focuses on common practices, interventions and strategies that have potential impact for the control of Salmonella along the poultry production continuum from farm to plate.

Effects of Lactobacillus fermentum Administration on Intestinal Morphometry and Antibody Serum Levels in Salmonella-Infantis-Challenged Chickens

There are no studies reporting the effects of Salmonella enterica subsp. enterica serovar Infantis (S. Infantis) on intestinal architecture and immunoglobulin serum levels in chickens. Here, we measured these parameters and hypothesized whether probiotic administration could modulate the observed outcomes. Two-hundred 1-day-old COBB 500 male chicks were allocated into four groups: (I) the control, (II) the group treated with L. fermentum, (III) the group exposed to S. Infantis, and (IV) the group inoculated with both bacteria. At 11 days post infection, blood was gathered from animals which were then euthanized, and samples from the small intestine were collected. Intestinal conditions, as well as IgA and IgM serum levels, were assessed. S. Infantis reduced villus-height-to-crypt-depth (VH:CD) ratios in duodenal, jejunal, and ileal sections compared to control conditions, although no differences were found regarding the number of goblet cells, muc-2 expression, and immunoglobulin concentration. L. fermentum improved intestinal measurements compared to the control; this effect was also evidenced in birds infected with S. Infantis. IgM serum levels augmented in response to the probiotic in infected animals. Certainly, the application of L. fermentum elicited positive outcomes in S. Infantis-challenged chickens and thus must be considered for developing novel treatments designed to reduce unwanted infections.

Qualitative Evaluation of Causes for Routine Salmonella Monitoring False-Positive Test Results in Dutch Poultry Breeding Flocks

The Salmonella monitoring program, as outlined in the EU Commission regulation 200/2010, asks for repeated sampling in order to ascertain progress in achievement of the EU target. According to Article 2.2.2.2.c of this regulation, the competent authority may decide to do a resample and retest when it has reasons to question the results of initial testing. In the Netherlands, the competent authorities have been resampling and retesting all initial positive samplings for several years because of doubts about false positive initial test results. An analysis of population data in the period 2015–2019 indicates that 48% of initial samplings at the farm were classified as false positive after resampling and retesting by the competent authorities. A qualitative analysis, assessing factors that could be associated with the occurrence of false positives, indicates that cross-contamination during the sampling process by the poultry farmer is probably the most likely source. Cross-contamination of samples during transport from the farm to the laboratory and/or cross-contamination at the laboratory are also considered possible sources. Given the slightly non-optimal system-specificity of the Salmonella monitoring program, there is good reason to make, or consider, standard resampling and retesting of initial positive results by the competent veterinary authorities possible within the EU.

Encapsulation of Cochleates Derived from Salmonella Infantis with Biopolymers to Develop a Potential Oral Poultry Vaccine

The aim of this study was to develop and characterize Salmonellaenterica serovar Infantis (S. Infantis) cochleates protected by encapsulation technology as a potential vaccine and to determine its safety in pullets. Cochleates were encapsulated by two technologies, spray drying and ionotropic gelation at different concentrations (0-15% v/v), and were characterized by physicochemical properties, protein content and Fourier Transform Infrared Spectroscopy (FTIR). The cochleates were white liquid suspensions with tubular shapes and a protein content of 1.0-2.1 mg/mL. After encapsulation by spray drying, microparticles ranged in size from 10.4-16.9 µm, were spherical in shape, and the protein content was 0.7-1.8 mg/g. After encapsulation by ionotropic gelation, beads ranged in size from 1620-1950 µm and were spherical in shape with a protein content of 1.0-2.5 mg/g. FTIR analysis indicated that both encapsulation processes were efficient. The cochleates encapsulated by ionotropic gelation were then tested for safety in pullets. No ill effect on the health of animals was observed upon physical or postmortem examination. In conclusion, this study was the first step in developing a potential oral S. Infantis vaccine safe for poultry using a novel cochleate encapsulation technology. Future studies are needed to determine the effectiveness of the vaccine.

Translating 'big data': better understanding of host-pathogen interactions to control bacterial foodborne pathogens in poultry

Recent technological advances has led to the generation, storage, and sharing of colossal sets of information ('big data'), and the expansion of 'omics' in science. To date, genomics/metagenomics, transcriptomics, proteomics, and metabolomics are arguably the most ground breaking approaches in food and public safety. Here we review some of the recent studies of foodborne pathogens (Campylobacter spp., Salmonella spp., and Escherichia coli) in poultry using big data. Genomic/metagenomic approaches have reveal the importance of the gut microbiota in health and disease. They have also been used to identify, monitor, and understand the epidemiology of antibiotic-resistance mechanisms and provide concrete evidence about the role of poultry in human infections. Transcriptomics studies have increased our understanding of the pathophysiology and immunopathology of foodborne pathogens in poultry and have led to the identification of host-resistance mechanisms. Proteomic/metabolomic approaches have aided in identifying biomarkers and the rapid detection of low levels of foodborne pathogens. Overall, 'omics' approaches complement each other and may provide, at least in part, a solution to our current food-safety issues by facilitating the development of new rapid diagnostics, therapeutic drugs, and vaccines to control foodborne pathogens in poultry. However, at this time most 'omics' approaches still remain underutilized due to their high cost and the high level of technical skills required.