The microbiota plays a vital role in maintaining gut health and influences the overall performance of chickens. Most gut microbiota-related studies have been performed in broilers, which have ...different microbial communities compared to those of layers. The normal gut microbiota of laying chickens is dominated by
,
,
,
, and
at the phylum level. The composition of the gut microbiota changes with chicken age, genotype, and production system. The metabolites of gut microbiota, such as short-chain fatty acids, indole, tryptamine, vitamins, and bacteriocins, are involved in host-microbiota cross talk, maintenance of barrier function, and immune homeostasis. Resident gut microbiota members also limit and control the colonization of foodborne pathogens. In-feed supplementations of prebiotics and probiotics strengthen the gut microbiota for improved host performance and colonization resistance to gut pathogens, such as
and
The mechanisms of action of prebiotics and probiotics come through the production of organic acids, activation of the host immune system, and production of antimicrobial agents. Probiotic candidates, including
,
,
,
, and
isolates, have shown promising results toward enhancing food safety and gut health. Additionally, a range of complex carbohydrates, including mannose oligosaccharides, fructo-oligosaccharides, and galacto-oligosaccharides, and inulin are promising candidates for improving gut health. Here, we review the potential roles of prebiotics and probiotics in the reshaping of the gut microbiota of layer chickens to enhance gut health and food safety.
The gut microbiota plays an important role in the colonisation resistance and invasion of pathogens.
Typhimurium has the potential to establish a niche by displacing the microbiota in the chicken gut ...causing continuous faecal shedding that can result in contaminated eggs or egg products. In the current study, we investigated the dynamics of gut microbiota in laying chickens during
Typhimurium infection. The optimisation of the use of an infeed probiotic supplement for restoration of gut microbial balance and reduction of
Typhimurium load was also investigated.
infection caused dysbiosis by decreasing (FDR < 0.05) the abundance of microbial genera, such as
,
,
,
,
,
and
and increasing the abundance of genera such as
,
,
and
. The higher
Typhimurium load resulted in lower (
< 0.05) abundance of genera such as
,
,
,
,
and
suggesting
driven gut microbiota dysbiosis. Higher
load led to increased abundance of genera such as
,
,
,
,
,
and
suggesting a positive interaction of these genera with
in the displaced gut microbiota. Probiotic supplementation improved the gut microbiota by balancing the abundance of most of the genera displaced by the
challenge with clearer effects observed with continuous supplementation of the probiotic. The levels of acetate and butyrate in the faeces were not affected (
> 0.05) by
challenge and the butyrate level was increased by the continuous feeding of the probiotic. Probiotic supplementation in
challenged chickens resulted in higher level of propionate. Continuous probiotic supplementation decreased (
< 0.05) the overall mean load of
in faeces and had a significant effect on
load reduction in internal organs.
challenge negatively impacts the diversity and abundance of many gut microbial genera involved in important functions such as organic acid and vitamin production. Strategic feeding of a
based probiotic helps in restoring many of the microbial genera displaced by
Typhimurium challenge.
Purpose of review
Nontyphoidal
Salmonella
is a major food safety concern in developed and developing countries. Table eggs are often linked to cases of foodborne gastrointestinal disease. This review ...is focused on the latest findings on foodborne
Salmonella
infections acquired from poultry products and their implications on food safety.
Recent findings
Salmonella
Enteritidis (SE) and
Salmonella
Typhimurium (ST) are the predominant
Salmonella
serovars associated with human Salmonellosis. In Australia, ST is the predominant serovar but SE has been recently detected in some commercial free-range egg flocks. The
Salmonella
shedding in poultry flocks can be highly variable across different flocks and farms; as a result, the level of product contamination is largely attributed to the flock management. The microevolution in the ST genome after in-vivo passaging may have clinical significance. On farm use of
Salmonella
vaccines and/or interventions during the processing of the product can influence the bacterial load. The refrigeration of the product also influences the safety of the poultry product.
Summary
Many interventions are in place for the control of
Salmonella
from farm to fork. However, given the biosecurity challenges because of the increase in public demand for free-range products, the emergence of
Salmonella
virulent types and expensive diagnostics, ongoing collaborative efforts from farmers, regulators and public health officials are required.
Positive modulation of gut microbiota in laying chickens may offer a strategy for reduction of
Salmonella
Typhimurium shedding and production of safer poultry products. In the current study, the ...caecal luminal microbiota of laying chicks was studied using 16S rRNA amplicon sequencing on DNA obtained from the chicks that were offered supplementation with commercial probiotics, synbiotics and/or
Salmonella
Typhimurium challenge. The load of
Salmonella
Typhimurium in various organs was quantified. Irrespective of the probiotics and synbiotics supplementation and
Salmonella
Typhimurium challenge, caecal microbiota was dominated by 22 distinct bacterial genera and 14 families that clustered into
Actinobacteria
,
Proteobacteria
and
Firmicutes
at phylum level. Taken together, probiotics and synbiotics supplementation increased (false discovery rate; FDR < 0.05) the abundance of
Ruminococcus
,
Trabulsiella
,
Bifidobacterium
,
Holdemania
and
Oscillospira
, indicating their role in maintaining gut health through lowering luminal pH and digestion of complex polysaccharides.
Salmonella
Typhimurium challenge decreased the abundance of
Trabulsiella
,
Oscillospira
,
Holdemania
,
Coprococcus
,
Bifidobacterium
and
Lactobacillus
and increased
Klebsiella
and
Escherichia
, indicating its role in caecal dysbiosis. Although probiotics and synbiotics supplementation positively modulated the caecal microbiota, they were not effective in significantly (
P
> 0.05) reducing
Salmonella
Typhimurium load in caecal tissue and invasion into vital organs such as liver and spleen. The early colonisation of laying chick caeca by probiotics and synbiotics had the potential to positively influence luminal microbiota; however, the microbial abundance and diversity were not sufficient to significantly reduce the shedding of
Salmonella
Typhimurium in faeces or invasion into internal organs during this study.
Temporal regulation of global gene expression in the caeca of chickens infected with
Salmonella
Typhimurium has not been investigated previously. In this study, we performed the transcriptome ...analysis of the caeca of
Salmonella
Typhimurium challenged chicks to understand the regulation of the mucosal immune system in a temporal manner. The
Salmonella
infection resulted in the activation of the caecal immune system by the upregulation of the differentially expressed genes (DEGs; false discovery rate (FDR) < 0.05; log
2
fold change > 1) involved in biological pathways such as Toll-like receptor signaling pathway,
Salmonella
infection, cytokine-cytokine receptor interaction, phagosome, apoptosis and intestinal immune network for IgA production. The activation of biological pathways such as RIG-I-like receptor signaling pathway, ErbB signaling pathway and cellular senescence showed a time-dependent response of the host immune system. A 49% increase in the DEGs on day 7 compared with day 3 post-infection (p.i.) suggested a time-dependent role of multiple genes such as
AvBD1, AvBD2, AvBD7
,
IL2
,
IL10, IL21, SIVA1
,
CD5
,
CD14
and
GPR142
in the regulation of the immune system. Nested network analysis of the individual biological pathways showed that
IL6
played a significant role in the immune system regulation by activating the pathways, including Toll-like receptor signaling pathway,
Salmonella
infection, intestinal immune network for IgA production and C-type lectin receptor signaling pathway. The downregulated DEGs (FDR < 0.05; log
2
fold change < −1) showed that
Salmonella
challenge affected the functions of pathways, such as tryptophan metabolism, retinol metabolism, folate biosynthesis and pentose and glucoronate interconversions, suggesting the disruption of cellular mechanisms involved in nutrient synthesis, absorption and metabolism. Overall, the immune response was temporally regulated through the activation of Toll-like signaling receptor pathway, cytokine-cytokine interactions and
Salmonella
infection, where
IL6
played a significant role in the modulation of caecal immune system against
Salmonella
Typhimurium.
Key points
•
The immune response to Salmonella Typhimurium challenge was temporally regulated in the caeca of chickens.
•
Many newly identified genes have been shown to be involved in the activation of the immune system.
•
Toll-like receptors and interleukins played a key role in immune system regulation.
The spin-chill process at poultry processing plants involves the immersion of chicken carcasses in cold water (<5°C) often containing sodium hypochlorite which significantly contributes to the ...reduction of bacterial loads. Cutting carcasses into pieces, however, has been linked with increases in Campylobacter and Salmonella counts. Here, the efficacy of PAA and ASC on reducing bacteria on skin-on, bone-in thigh cuts was investigated. Three concentrations of ASC (60, 112, and 225 ppm) and PAA (50, 75, 100 ppm) were used. Thighs were dipped into sanitizer and tested for total viable bacterial counts, Campylobacter load, and prevalence of Salmonella. The efficacy of PAA and ASC was also compared with chlorine (8 ppm). All sanitizers exhibited a greater log reduction compared with water. PAA at both 75 and 100 ppm resulted in significantly higher log reductions compared with the water only. PAA at 100 ppm and 225 ppm ASC were the most effective at reducing Campylobacter. All wash treatments reduced the proportion of Salmonella positive samples, but the greatest reduction was observed for 225 ppm ASC. Both concentrations of ASC resulted in a greater reduction in total viable counts compared with chlorine.
Salmonella is an important foodborne pathogen, causing an estimated 11,992 cases of infection in Australia per year. Egg or egg product related salmonellosis is a major concern for the egg industry. ...Worldwide, S. Typhimurium is one of the most common serovars identified in Salmonella food poisoning cases. The current study investigated the ability of five S. Typhimurium strains to penetrate washed and unwashed eggs using whole egg and agar egg penetration methods. All S. Typhimurium strains were able to penetrate eggshells and survive in egg albumen (at 20°C) according to whole egg penetration results. Polymerase Chain Reaction results demonstrated that S. Typhimurium strain 2 (10(3) and 10(5) CFU/mL), and strain 5 (10(3) and 10(5) CFU/mL) egg penetration was significantly higher (p<0.05) in washed eggs when compared to unwashed eggs. Statistical analysis of the agar penetration experiment indicated that S. Typhimurium was able to penetrate washed eggs at a significantly higher rate when compared to unwashed eggs (p<0.05). When compared to unwashed eggs, washed eggs also had significantly damaged cuticles. Statistical analysis also indicated that eggshell penetration by S. Typhimurium was related to various eggshell ultrastructural features such as cap quality, alignment, erosion, confluence, Type B bodies and cuticle cover.
Egg quality was measured in eggs from different flocks that were reared together and then allocated to different production systems. Eggs were processed for measurements of eggshell and egg internal ...quality variables, scoring of ultrastructural mammillary layer features, completeness of cuticle cover, and protoporphyrin IX (PP IX) quantification. There was a significant main effect (P < 0.05) of production system on shell reflectivity, egg weight, and egg internal quality and significant effects of flock age on most measurements. The mammillary layer ultrastructural variables showed no clear relationship with production system and flock age. However, there was a significant interaction between production system and flock age for mammillary cap, early and late fusions. Cuticle cover (Formula: see text), was significantly higher in barn eggs (19.20), followed by free range (17.57), and cage eggs (15.99). Completeness of cuticle cover was significantly higher in eggs from the 44 week old flock than for 64 week and 73 week old flocks. For eggshells with cuticle intact, there was a significant main effect of both production system and flock age, and significant interaction between the two, for shell reflectivity, L*a*b* values and amount of PP IX. For PP IX, when this difference was calculated for the cuticle alone, there were no statistically significant differences. In 1 g of shell with and without cuticle, there was more PP IX in cage eggs (9.49 × 10
, 7.90 × 10
mM) followed by free range (8.24 × 10
, 6.90 × 10
mM), and barn eggs (8.64 × 10
, 7.28 × 10
mM). Similar trends were recorded for the amount of PP IX in 1 g of cuticle, but the difference was not statistically significant. The amount of PP IX decreased significantly with increasing flock age. Comparing the cage and barn production systems at 68 week of flock age, there was no difference for the amount of PP IX in shell with or without cuticle, or in the cuticle alone. Eggs from the cage production system were darker in color and contained more PP IX mainly within the calcareous part of the shell. For the barn production system, the completeness of cuticle cover was higher and egg weight generally lower.
In Australia and other parts of the world, contaminated eggs or egg-containing food products are common vehicles for human Salmonella outbreaks. Recently, an uncommon serotype, Salmonella Hessarek, ...has emerged in foodborne salmonellosis due to the consumption of contaminated eggs and egg products. Limited research is available on the behaviour of Salmonella Hessarek in eggs. Therefore, this study was performed to understand the penetration ability and transcriptional behavior of Salmonella Hessarek in table eggs stored at different temperatures. The assay revealed that the penetration ability of Salmonella Hessarek was significantly (P < 0.05) affected by the egg storage temperature. Salmonella penetration into egg contents was significantly higher in cold (collected 3 h post-oviposition) compared with warm (collected immediately post-oviposition) eggs stored at 25 °C. There was 4 and 2.39 log increase in Salmonella cells in yolk and albumen, respectively, of the eggs stored at ambient temperature. The gene expression data indicated that genes regulate the pathways involved in stress and metabolism, such as yafD, proP, rpoS, phoP, adkF, and purG were significantly upregulated in yolk and on the eggshell surface, at refrigerated temperature. The gene expression data suggested that at refrigerated temperature, Salmonella Hessarek maintained its cell viability through upregulating the key genes necessary for survival. The findings further showed that not all genes involved in the vital functions of Salmonella were consistently regulated at 5 °C and 25 °C in different egg contents. This study revealed that Salmonella Hessarek has the capacity to penetrate and survive in eggshell pores. Storage of eggs at refrigerated temperature can reduce the penetration and replication risk of Salmonella Hessarek in eggs.
•Salmonella Hessarek can survive in eggshell pores.•Ambient temperature enhances the eggshell penetration of Salmonella Hessarek.•Egg refrigeration immediately after lay reduces the rate of bacterial penetration.•Genes regulating the stress pathway influence Salmonella Hessarek survival in eggs.
Single-aged caged layer hen flocks were monitored for Salmonella over the course of their lifetime. Chicks from both flocks were Salmonella negative at hatch and remained negative during rearing. ...Pullets were transported to production farms at 15 weeks of age. Pre-population dust swabs collected from both production sheds had a high percentage of Salmonella positive samples (80 and 90%). Flocks were sampled at regular intervals until 70–72 weeks of age. The proportion of Salmonella positive samples and mean load detected on eggs was low on both farms. Analysis of dust samples revealed that Salmonella persisted in dust over 8 weeks. Dust total moisture content and water activity appears to influence bacterial persistence. On egg grading equipment, only suction cups prior to egg washing were Salmonella positive (mean proportion Salmonella positive samples 0.13 ± 0.07; mean load of 18.6 ± 12.31 MPN/ml). An egg washing experiment demonstrated that while washing reduced the total Salmonella load from eggshell surfaces, no effect was observed for shell pores. These results demonstrate that despite environmental contamination on farm, Salmonella contamination of eggs is low and is further minimized by washing.
•Layer hen flocks were sampled for Salmonella from hatch to the end of production.•At hatch, chicks were Salmonella negative and remained negative during rearing.•Dust and egg belt samples had the highest proportion of Salmonella positive samples.•Egg washing reduced Salmonella on eggshells but not shell pores.•Improved dust control would help reduce the bacteria on farm.
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