Correlating bacterial shedding with fecal corticosterone levels and serological responses from layer hens experimentally infected with Salmonella Typhimurium

Nontyphoidal Salmonella infections acquired from poultry

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.

Effects of probiotic (Lactobacillus plantarum and Bacillus subtilis) supplementation on mortality, growth performance, and carcass characteristics of native Vietnamese broilers challenged with Salmonella Typhimurium

Background and Aim:

Probiotic species have been proven to be beneficial on broiler performance; however, most studies have focused on industrial chickens with fast growth, whereas little information concerning the use of these species on native chickens is available. This study aimed to investigate the effects of probiotics Lactobacillus plantarum (LP) and Bacillus subtilis (BS) on the mortality, growth rate, and carcass characteristics in native Noi chickens challenged with Salmonella Typhimurium.

Materials and Methods:

We divided 420 1-day-old Noi chicks into seven different treatment groups (n = 60): negative control (no S. Typhimurium, no probiotics or antibiotics); positive control (PC, S. Typhimurium infection, no probiotics or antibiotics); and S. Typhimurium infection and supplementation with LP, BS, LP + BS, enrofloxacin, and commercial probiotics, respectively. Treatment was for 96 days, and the chicks were orally challenged with S. Typhimurium at 22 days old.

Results:

No deaths occurred during the 4 weeks post-infection in the negative control, LP, or LP+BS groups. The PC group had the highest mortality rate (20%). Re-isolation of S. Typhimurium from the liver, spleen, and heart showed reduced bacterial counts at 1 week post-infection in the LP, BS, and LP + BS groups. The lowest body weight gain was observed in the PC group (949 g/bird), and chicks in the LP group gained 1148 g/bird. An improved feed conversion ratio was noted in the groups receiving probiotic supplementation (3.42–3.50 kg feed/kg gain). There was little evidence that probiotics affected carcass percentage and related parameters, such as breast, thigh and drumstick, and wings.

Conclusion:

Lactobacillus plantarum or BS dietary supplementation to native Noi broilers resulted in a lower mortality rate and improved body weight gain but did not affect carcass characteristics.

Effects of Supplemental Chromium Nanoparticles on IFN-γ expression of Heat Stress Broilers

The aim of present study was to investigate the beneficial effect of chromium (III) picolinate (CrPic) and chromium (III) picolinate nanoparticles (NCrPic) addition on growth performance, stress-related hormonal changes, and serum levels of various immunity biomarkers, as well as the gene expression of IFN-γ in broilers exposed to heat stress conditions. Treatments included T1 which received the basal diet with no feed additive; T2 exposed to heat stress; T3, T4, and T5 containing 500, 1000, and 1500 ppb CrPic; as well as T6, T7, and T8 containing 500, 1000, and 1500 ppb NCrPic, respectively. After 2 weeks from CrPic and NCrPic supplementation, IFN-γ mRNA expression was assayed using the RT-PCR technique. The results showed that the lower body weight, daily weight gain, daily feed intake by heat stress, and the feed conversion ratio were recovered remarkably by CrPic and NCrPic supplements. The stress-elevated levels of cortisol and immunoglobulin were reduced significantly using CrPic and NCrPic supplementation (P ≤ 0.05). The gene expression profile showed that the upregulated expression of IFN-γ was regulated by the addition of CrPic and NCrPic, in particular, to the diet; however, a full downregulation of IFN-γ expression was observed after week 2 of NCrPic supplementation. In conclusion, the results indicated that nanoparticle supplementation could be effective in reducing heat stress-induced detrimental alterations, thereby attributing to substantial changes to the immune system, including IFN-γ expression.

Over Time Decay of Cortisol Metabolites in Faecal Pellets of Koalas in Central Queensland

Simple Summary

Faecal cortisol metabolites (FCMs) are a useful, non-invasive tool for the assessment of stress in koalas. However, FCM stability after defecation is a critical issue. Therefore, we exposed faecal pellets of koalas to three different environmental conditions and measured FCMs with three recently evaluated enzyme immunoassays (EIAs). Because water loss over time exerted the greatest influence on FCMs, we strongly recommend collecting freshly defecated pellets in koalas.

Abstract

Faecal material can be a valuable source of information for a range of animal health aspects and can be used to measure faecal cortisol metabolites (FCMs). FCM values can relate to physiological stress responses. However, freshly defecated pellets are not always available and environmental conditions, such as temperature and humidity, might affect faecal pellet consistency and FCM levels. Therefore, the impact of environmental conditions on FCMs needs to be evaluated. We collected 107 pellets from two female and two male koalas, exposed them to three types of treatments, and analysed FCMs in these samples with three enzyme immunoassays (EIAs). After analysis, the original FCM values were mathematically corrected for water loss. Results show that the FCMs were more stable when measured using tetrahydrocorticosterone (50c) and 5α-pregnane-3β,11β,21-triol-20-one (37e) EIAs, and were less stable when measured with the cortisol EIA. With 50c, the FCM values did not vary significantly over time either before or after the adjustment with water in the environment treatment group. For samples kept under constant low (25 °C) and high (35 °C) temperatures, the 50c FCM values did not vary significantly over time, after adjustments were made for water loss. Thus, this study highlights the importance of considering the suitability of faecal field samples for FCM analysis. Because water loss was the main driver of FCM changes, we strongly recommend collecting koala pellets that are freshly defecated, despite the effort and time it might take to collect such pellets.

Understanding the effects of intramuscular injection and feed withdrawal on Salmonella Typhimurium shedding and gut microbiota in pullets

Background

Gut microbiota plays a key role in health, immunity, digestion, and production in layers. Factors such as environment, diet, diseases, stress, and flock management significantly affect gut microbiota; however, it is not known how potential stressors such as intramuscular injections or feed withdrawal alter the composition of gut microbiota that result in increased the shedding level of foodborne pathogens. In the current study, the effects of intramuscular corticosterone injection and feed withdrawal were evaluated to understand their role in Salmonella Typhimurium shedding and changes in the composition of gut microbiota in layers.

Results

Salmonella shedding was observed for 8 weeks post-infection. There was a significant increase in Salmonella Typhimurium count after intramuscular injection and feed withdrawal. The Salmonella infected and the negative control groups showed significant differences in the abundance of different genera in gut microbiota at week 1 and up to week 7 post infection. The infected group showed a significant reduction in alpha diversity of gut microbiota. Firmicutes reduced significantly (P < 0.05) after intramuscular injection, while the feed withdrawal groups did not cause any significant changes in Proteobacteria-Firmicutes ratio. Furthermore, intramuscular injection resulted in a significant change in alpha diversity of gut microbiota.

Conclusions

Exposure of chicks to relatively low dose of Salmonella Typhimurium can lead to persistent shedding in pullets. The Salmonella Typhimurium infection disrupted the gut microbiota composition immediately after infection. The potential stress of intramuscular injection and feed withdrawal significantly increased the Salmonella Typhimurium count in faeces. The intramuscular injection also resulted in a significant alteration of the Proteobacteria-Firmicutes ratio, which could increase the risk of dysbiosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00597-9.

The Simultaneous Administration of a Probiotic or Prebiotic with Live Salmonella Vaccine Improves Growth Performance and Reduces Fecal Shedding of the Bacterium in Salmonella-Challenged Broilers

Salmonellosis is one of the most important bacterial diseases in poultry, causing heavy economic losses, increased mortality and reduced production. The aim of this study was the comparative efficacy of a commercial probiotic and/or prebiotic with a live attenuated Salmonella Enteritidis (SE) vaccine on the protection of broiler chickens from SE challenge. The efficacy of probiotic or prebiotic products, as well as a live Salmonella Enteritidis (SE) vaccine at the 7th day of age, administered via drinking water, were evaluated for clinical protection and effects on growth performance of broiler chickens experimentally challenged with SE at the 28th day of age. The use of probiotic or prebiotic simultaneously with the live Salmonella vaccine can diminish the negative effect of live vaccine growth performance, reducing mortality rate, fecal shedding, and re-isolation of SE from liver, spleen, heart and cecum. The use of probiotic or prebiotic simultaneously with the application of the live Salmonella vaccine is a good practice to diminish the negative effect of the harmful bacteria and improve the growth performance of broilers. Thus, further studies may be carried out with layers and breeders.

Astragalus polysaccharides attenuated inflammation and balanced the gut microflora in mice challenged with Salmonella typhimurium

Salmonella typhimurium (S. t.) is one of the main pathogens that causes acute gastroenteritis. To evaluate the anti-inflammatory mechanism of Astragalus polysaccharide (APS) in vivo and its influence on the intestinal flora, BALB/c mice were infected with S. t. to establish a model of diarrhea. The disease activity index (DAI) scores showed that APS attenuated S. t.-induced weight loss and diarrhea in mice. APS significantly reduced the index of the liver and spleen as well as the ALT and AST levels in serum (P < 0.05). Hematoxylin and eosin (H&E) results indicated that APS significantly increased jejunum villus height and crypt depth and reduced the infiltration of inflammatory cells (P < 0.05). Additionally, APS increased the tight junction (TJ) proteins expression levels of ZO-1, Occludin and Claudin-1 in the jejunum. The results of 16S rDNA showed that APS significantly increased the number of Lactobacillus and Bifidobacterium spp. to normal levels (compared with the control group). In addition, APS significantly decreased the mRNA expression levels of the proinflammatory cytokines TNF-α, IL-1β, IL-6 and IL-17 in the jejunum (P < 0.01) as well as the proteins expression levels of COX-2 and iNOS (P < 0.05). Western blot confirmed that prefeeding with APS inhibited S. t.-induced expression of TLR4 and MyD88 in the jejunum and further inhibited nuclear factor-κB (NF-κB) activation, including the nuclear translocation of the p65 NF-κB subunit and the phosphorylation and degradation of IκB-α. This was the key to APS inhibition of the production of inflammatory factors and inflammatory mediators in the jejunum.

Unpredictable Chronic Mild Stress Suppresses the Incorporation of New Neurons at the Caudal Pole of the Chicken Hippocampal Formation

In the mammalian brain, adult hippocampal neurogenesis (AHN) is suppressed by chronic stress, primarily at the ventral pole of the hippocampus. Based upon anatomy, we hypothesise that the caudal pole of the avian Hippocampal Formation (HF) presents a homologous subregion. We thus investigated whether AHN is preferentially suppressed in the caudal chicken HF by unpredictable chronic mild stress (UCMS). Adult hens were kept in control conditions or exposed to UCMS for 8 weeks. Hens experiencing UCMS had significantly fewer doublecortin-positive multipolar neurons (p < 0.001) and beaded axons (p = 0.021) at the caudal pole of the HF than controls. UCMS birds also had smaller spleens and lower baseline plasma corticosterone levels compared to controls. There were no differences in AHN at the rostral pole, nor were there differences in expression of genetic mediators of the HPA stress response in the pituitary or adrenal glands. Duration of tonic immobility and heterophil/lymphocyte (H/L) ratios were also not responsive to our UCMS treatment. These results support the hypothesised homology of the caudal pole of the avian HF to the ventral pole of the rodent hippocampus. Furthermore, quantifying neurogenesis in the caudal HF post-mortem may provide an objective, integrative measure of welfare in poultry, which may be more sensitive than current welfare measures.

Purification of recombinant IpaJ to develop an indirect ELISA-based method for detecting Salmonella enterica serovar Pullorum infections in chickens

Background

Salmonella enterica serovar Pullorum is a host-restricted serotype causing infection in poultry. The pathogen can not only cause acute infection in young chicks with high mortality and morbidity, but also persist in adult chickens without evident clinical symptoms and lead to vertical transmission. To eradicate S. Pullorum in poultry farms, it is necessary to establish an efficient method to monitor the prevalence of the pathogen in adult chickens. The protein IpaJ is a specific immunogen in S. Pullorum and is not detected in closely related serotypes, such as S. Gallinarum and S. Enteritidis.

Results

In the present study, IpaJ was expressed as a recombinant fusion protein MBP-IpaJ in E. coli. The purified MBP-IpaJ was used as a coating antigen to develop an indirect ELISA assay, which was applied to the detection of S. Pullorum infection in chickens. The indirect ELISA assay demonstrated that antibodies produced against IpaJ were detectable in antisera of chickens infected with S. Pullorum in the second week, stably increased until the tenth week, and persisted at a high level in the following two weeks. Furthermore, the ELISA method detected four positive samples out of 200 clinical antiserum samples collected from a poultry farm, and the positive samples were confirmed to be reacted with S. Pullorum using the standard plate agglutination test.

Conclusions

The established indirect ELISA using the IpaJ protein is a novel method for specific detection of S. Pullorum infection, and contribute to eradication of pullorum disease in the poultry industry.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1753-0) contains supplementary material, which is available to authorized users.

Shedding of Salmonella Typhimurium in vaccinated and unvaccinated hens during early lay in field conditions: a randomised controlled trial

Background

Salmonella vaccination is one of the control measure that farmers can use to reduce bacterial shedding in their flocks. This study aimed to examine the efficacy of the Vaxsafe® ST (Strain STM-1) attenuated live vaccine administered as ocular and oral doses followed by an intramuscular (IM) dose in rearing, in reducing contamination by Salmonellae of both eggs and the environment in the commercial multi-age cage layer sheds. A randomised controlled trial was conducted up to 26 weeks post last vaccine on two different multi-age caged egg farms.

Results

No clinical symptoms were observed following IM administration of STM-1 during rearing. Following the first two STM-1 doses, both vaccinated and unvaccinated birds exhibited antibody titres below the positive cut-off value, however after IM administration of STM-1, antibody titres in the vaccinated group were above the cut-off value. Wild type Salmonella Typhimurium was not detected during the rearing of pullets. During production, the antibody titres were significantly higher in the vaccinated group at all sampling points during this trial. There was no significant difference in the prevalence of Salmonella (detected by culture and PCR method) between the vaccinated and unvaccinated groups on the egg belt and faeces in early lay. Wild-type Salmonella spp. were consistently found in dust samples. Quantitative PCR (qPCR) assay was able to differentiate between the live vaccine strain and wild type Salmonella. The load of wild-type Salmonella in shed environment was relatively low (1.3 log₁₀ ± 0.48 CFU/m² of surface area).

Conclusion

Given that Salmonella Typhimurium and other serovars are able to survive/persist in the shed environment (such as in dust), regular cleaning and or removal of dust from shed is important. Use of the Vaxsafe® ST vaccine in multi-age flocks is “not an ultimate intervention” for reduction of Salmonella Typhimurium because of the complexities involved in achieving control, such as the efficacy of cleaning of sheds, the lack of resting periods between batches and the possible carry over of contamination from existing flocks. Hence implementation of more than one or several interventions strategies is essential.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1201-0) contains supplementary material, which is available to authorized users.

A Long-Term Efficacy Trial of a Live, Attenuated Salmonella Typhimurium Vaccine in Layer Hens

Salmonella remains one of the most common causes of bacterial foodborne gastrointestinal disease in humans. Raw eggs or food items containing undercooked eggs are frequently identified as the source of Salmonella. Salmonella Typhimurium contamination of table eggs most commonly occurs when they are laid in a contaminated environment. Several control strategies, including vaccination, are widely used to mitigate the total Salmonella load. It is unclear, however, whether live attenuated Salmonella vaccines are efficacious over the life span of a layer hen. Live attenuated Salmonella vaccines have been favored due to their ability to illicit a strong humoral immune response. The lifespan of a layer hen ranges between 60 and 80 weeks and the long term efficacy of attenuated vaccine strains has not been investigated. In this study, commercial brown layer chicks were vaccinated at day old, 6 weeks of age, and again at 10 weeks of age with the Bioproperties Vaxsafe^TM STM1 aroA mutant vaccine. Birds were challenged at 18 weeks of age with Salmonella Typhimurium DT9 (MLVA 03 15 08 11 550). Feces and eggs were monitored for S. Typhimurium for 40 weeks post-infection. Birds produced a strong immune response following the final dose which was administered intramuscularly. The serum antibody response to S. Typhimurium DT9 infection did not differ between challenged groups. Fecal shedding and egg contamination was highly variable and did not differ significantly between vaccinated and unvaccinated birds that had been challenged with S. Typhimurium DT9. Total bacterial load in feces was quantified using qPCR. No significant difference was detected between unvaccinated and vaccinated birds after challenge.

Detection of Salmonella Infection in Chickens by an Indirect Enzyme-Linked Immunosorbent Assay Based on Presence of PagC Antibodies in Sera

The outcomes of infection of humans and animals with Salmonella range from a persistent asymptomatic carrier state to temporal mild gastroenteritis or severe systemic infection. A rapid and accurate diagnostic test would help formulate strategies for effective prevention of their infections in the animal population. Current sequencing data predict that the outer membrane protein, PagC, is present in all common Salmonella serovars with sequence similarities of more than 98%. PagC sequences in other bacterial species are less than 65% similarity at the amino acid level to those of Salmonella PagC. We hypothesized that PagC could be immunogenic and detection of antibodies to this protein could be an accurate indicator of Salmonella infection. The pagC gene from Salmonella enterica serovar Typhimurium CVCC542 was expressed in Escherichia coli. The purified recombinant PagC protein was immobilized in microtiter plate wells. Sera from SPF chickens infected with Salmonella or other non-Salmonella pathogens by injection were added and binding of PagC protein was detected by the horseradish peroxidase (HRP)-labeled goat anti-chicken antibody. Sera from Salmonella-infected chickens showed high specificity in contrast to the sera from chickens infected with other bacteria. When 87 Salmonella antibody-positive sera from Salmonella Pullorum orally infected SPF chicken and 93 negative sera from uninfected SPF chicken were tested, 98.3% agreement was detected. The rPagC enzyme-linked immunosorbent assay (ELISA) and agglutination had 80.6% agreement in detecting 252 clinical chicken sera samples. These results suggest that PagC antibody-based indirect ELISA can serve as a convenient and novel method for the diagnosis of Salmonella infection.