Assessment of 2 Salmonella enterica serovar Typhimurium-based vaccines against necrotic enteritis in reducing colonization of chickens by Salmonella serovars of different serogroups

This study assessed the protective efficacy of oral vaccination with 2 experimental attenuated Salmonella Typhimurium-vectored vaccines for necrotic enteritis in protecting chickens against intestinal colonization by common serovars of Salmonella belonging to the 4 major serogroups affecting chickens. Birds were vaccinated orally with 1 × 10⁸ colony-forming units (CFU) of 1 of the vaccine strains χ9241 and χ9352, which express a plasmid-encoded partial recombinant hypothetical protein gene (tHP) of Clostridium perfringens, at days 1 and 7 of age, and then were challenged at 14 d of age with 10⁶ CFU of Salmonella serovars Anatum, Enteritidis, Heidelberg, Kentucky, or Typhimurium (representative serovars of serogroups B, C, D, and E). Birds were necropsied at 4 wk of age, and samples were collected to determine reduction in tissue and intestinal colonization. The chickens vaccinated with χ9241-tHP showed reduced colonization by Salmonella Enteritidis (serogroup D) and by Salmonella Heidelberg and Salmonella Typhimurium (serogroup B) compared with the control birds. No reduction in colonization was observed in the chickens vaccinated with χ9352-tHP. There was an association between the efficacy of these vaccine strains in protecting against necrotic enteritis, assessed on an earlier occasion, and their efficacy in protecting against Salmonella colonization. Thus, the choice of an attenuated Salmonella Typhimurium vaccine vector for delivery of heterologous antigens to chickens should be based partly on the vaccine’s value in protecting against colonization by serovars within serogroups B and D. Such vectors would have the additional benefit of reducing colonization of important Salmonella serovars.     

In ovo leptin administration affects hepatic lipid metabolism and microRNA expression in newly hatched broiler chickens

Background

A leptin-like immunoreactive substance has been found in chicken eggs and has been implicated in serving as a maternal signal to program offspring growth and metabolism. In the present study, we investigated the effects of in ovo leptin administration on hatch weight, serum and hepatic concentrations of metabolites and hormones, as well as on the expression of genes involved in hepatic lipid metabolism and the predicted microRNAs (miRNAs) targeting the affected genes. To this end we injected fertile eggs with either 0.5 μg of recombinant murine leptin or vehicle (PBS) before incubation.

Results

Prenatally leptin-exposed chicks showed lower hatch weight, but higher liver weight relative to the body weight, compared to the control group. In ovo leptin treatment increased the hepatic content and serum concentration of leptin in newly hatched chickens. The hepatic contents of triglycerides (TG) and total cholesterol (Tch) were decreased, whereas the serum levels of TG, Tch and apolipoprotein B (ApoB) were increased. The hepatic mRNA expression of sterol regulator element binding protein 1 (SREBP-1c), SREBP-2, hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and cholesterol 7α-hydroxylase 1 (CYP7A1) was significantly up-regulated, as was the protein content of both SREBP-1c and SREBP-2 in hepatic nuclear extracts of leptin-treated chickens. Moreover, out of 12 miRNAs targeting SREBP-1c and/or HMGCR, five were significantly up-regulated in liver of leptin-treated chicks, including gga-miR-200b and gga-miR-429, which target both SREBP-1c and HMGCR.

Conclusions

These results suggest that leptin in ovo decreases hatch weight, and modifies hepatic leptin secretion and lipid metabolism in newly hatched broiler chickens, possibly via microRNA-mediated gene regulation.     

Gene expression in the chicken caecum in response to infections with non-typhoid Salmonella

Chickens can be infected with Salmonella enterica at any time during their life. However, infections within the first hours and days of their life are epidemiologically the most important, as newly hatched chickens are highly sensitive to Salmonella infection. Salmonella is initially recognized in the chicken caecum by TLR receptors and this recognition is followed by induction of chemokines, cytokines and many effector genes. This results in infiltration of heterophils, macrophages, B- and T-lymphocytes and changes in total gene expression in the caecal lamina propria. The highest induction in expression is observed for matrix metalloproteinase 7 (MMP7). Expression of this gene is increased in the chicken caecum over 4000 fold during the first 10 days after the infection of newly hatched chickens. Additional highly inducible genes in the caecum following S. Enteritidis infection include immune responsive gene 1 (IRG1), serum amyloid A (SAA), extracellular fatty acid binding protein (ExFABP), serine protease inhibitor (SERPINB10), trappin 6-like (TRAP6), calprotectin (MRP126), mitochondrial ES1 protein homolog (ES1), interferon-induced protein with tetratricopeptide repeats 5 (IFIT5), avidin (AVD) and transglutaminase 4 (TGM4). The induction of expression of these proteins exceeds a factor of 50. Similar induction rates are also observed for chemokines and cytokines such as IL1β, IL6, IL8, IL17, IL18, IL22, IFNγ, AH221 or iNOS. Once the infection is under control, which happens approx. 2 weeks after infection, expression of IgY and IgA increases to facilitate Salmonella elimination from the gut lumen. This review outlines the function of individual proteins expressed in chickens after infection with non-typhoid Salmonella serovars.     

Only one of the two type VI secretion systems encoded in the Salmonella enterica serotype Dublin genome is involved in colonization of the avian and murine hosts

The type VI secretion system (T6SS) is a virulence factor for many Gram-negative bacteria. Salmonella genus harbors five phylogenetically distinct T6SS loci encoded in Salmonella Pathogenicity Islands (SPIs) SPI-6, SPI-19, SPI-20, SPI-21 and SPI-22, which are differentially distributed among serotypes. The T6SSs encoded in SPI-6 and SPI-19 contribute to pathogenesis of serotypes Typhimurium and Gallinarum in mice and chickens, respectively. Salmonella Dublin is a pathogen restricted to cattle where it causes a systemic disease. Also, it can colonize other hosts such as chickens and mice, which can act as reservoirs of this serotype. Salmonella Dublin harbors the genes for both T6SS_SPI-6 and T6SS_SPI-19. This study has determined the contribution of T6SS_SPI-6 and T6SS_SPI-19 to host-colonization by Salmonella Dublin using avian and murine models of infection. Competitive index experiments showed that, a mutant strain lacking both T6SSs (∆T6SS_SPI-6/∆T6SS_SPI-19) presents a strong colonization defect in cecum of chickens, similar to the defect observed for the ∆T6SS_SPI-6 mutant, suggesting that this serotype requires a functional T6SS_SPI-6 for efficient colonization of the avian gastrointestinal tract. Colonization of mice was also defective, although to a lesser extent than in chickens. In contrast, the T6SS_SPI-19 was not necessary for colonization of either chickens or mice. Transfer of T6SS_SPI-6, but not T6SS_SPI-19, restored the ability of the double mutant to colonize both animal hosts. Our data indicate that Salmonella Dublin requires only the T6SS_SPI-6 for efficient colonization of mice and chickens, and that the T6SS_SPI-6 and T6SS_SPI-19 are not functionally redundant.     

Colonization characteristics of Campylobacter jejuni in chick ceca

We report our findings on several parameters influencing cecal colonization of chickens by Campylobacter jejuni. Thirty-five colony-forming units (CFU) of a composite culture of C. jejuni colonized the ceca of one-half of the newly hatched chicks challenged by oral gavage. A challenge dose of 3500 CFU/chick consistently colonized the ceca of all chicks challenged. Challenge doses of approximately 10(5) CFU of C. jejuni per chick resulted in consistent cecal colonization, regardless of whether the birds were challenged 1, 2, or 3 days post-hatch. Four isolates showed consistently strong cecal colonization abilities, whereas two isolates colonized the ceca in only 20 of 122 chicks when given levels of 10(5) CFU per chick. One of these poorly colonizing isolates was repeatedly transferred by fecal-oral passage through chicks; subsequently, this isolate was able to consistently colonize chicks. Competitive exclusion (CE) microflora did not diminish the colonization rates for C. jejuni. Birds treated with five different CE cultures were colonized at a rate of 81 of 84 chicks; control chicks were similarly consistently colonized (45 of 46 chicks).     

Effect of a mannanoligosaccharide-supplemented diet on intestinal mucosa T lymphocyte populations in chickens challenged withSalmonella Enteritidis

Salmonellosis is one of the most common worldwide zoonosis, and the Enteritidis and Typhimurium serotypes are most prevalent. In this study, we evaluated the effects of a diet supplemented with mannanoligosaccharides (MOS) on CD3+, CD4+, CD8+, and goblet cell counts in the intestines of broilers vaccinated and challenged withSalmonella Enteritidis. The evaluation was based on randomized experiments including 45 chickens divided into 3 experimental groups. Group 1 received a nonsupplemented control diet. Group 2 received a diet supplemented with 1 kg MOS/t from d 1 to 21 and 0.5 kg MOS/t from d 22 to 56. Group 3 received a diet supplemented with 2 kg MOS/t from d 1 to 21 and 1 kg MOS/t from d 22 to 56. Chickens fed the lower level of MOS demonstrated reduced fecal shedding ofSalmonella 14 d after being challenged (P < 0.05). Both groups of MOS-supplemented chickens showed an increase in CD4+ and CD8+ cell counts in the ileal and cecal mucosa after being challenged withSalmonella Enteritidis (SE). Supplementation with MOS increased the specific T lymphocyte infiltration in the intestinal mucosa of chickens vaccinated and challenged withSalmonella Enteritidis.     

初雏接种益生菌对雏鸡肠道菌群的影响

本试验研究了使用竞争排斥类益生菌制剂(CE)对初生雏鸡肠道菌群的影响。试验一随机将180只刚出壳雏鸡分为两组,试验组在0d每只口服接种益生菌106CFU,而对照组则口服无菌生理盐水。通过选择性培养和DGGE带型分析,研究不同日龄雏鸡盲肠内容物中菌群结构的变化。结果表明:试验和对照组的细菌总数差异不显著,试验组的大肠杆菌数显著低于对照组(P<0.05),试验组的乳酸杆菌数高于对照组;肠球菌数低于对照组,但二者差异不显著。PCR-DGGE结果表明试验组的电泳条带明显多于对照组,而且两组肠道菌群按不同处理明显地聚类成两大分支,说明初雏接种益生菌可以影响后期的盲肠菌群结构。试验二的分组和0d处理同试验一,两组随后在1d均口服接种鼠伤寒沙门氏菌。通过检测沙门氏菌和耐药性大肠杆菌定植数量来比较益生菌对雏鸡的保护率。结果表明:在12d,对照组盲肠内沙门氏菌阳性率为46.15%,而试验组则未检出。同时,与对照组相比,试验组盲肠内耐30ppm卡那霉素和5ppm氨苄青霉素的大肠杆菌数量下降显著。以上结果显示,竞争排斥类益生菌制剂不仅可在雏鸡肠道内成功定植,而且可以显著降低肠道沙门氏菌的数量。     

Antibacterial Effect of Trans-Cinnamaldehyde on Salmonella Enteritidis and Campylobacter jejuni in Chicken Drinking Water,

Salmonella Enteritidis and Campylobacter jejuni are 2 major foodborne pathogens in the United States, estimated to cause more than 3 million cases of human illness annually. Chickens are the natural hosts of these bacteria, and their drinking water can be a source of S. Enteritidis and C. jejuni, contributing to the colonization of birds. In this study, trans-cinnamaldehyde (TC), a natural, generally recognized as safe ingredient in cinnamon oil was evaluated for its efficacy to inactivate S. Enteritidis and C. jejuni in the drinking water of chickens. Well water containing 0, 0.016, 0.03, and 0.06% TC was inoculated with a 5-strain mixture of S. Enteritidis or C. jejuni (˜6 log₁₀ cells/mL). Water samples containing 1% chicken feces or feed were also included. The samples were incubated at 12.5 or 25°C for 7 d and analyzed for bacterial populations on d 0, 1, 3, 5, and 7. Duplicate samples of treatments and control were included, and the study was replicated 3 times. Trans-cinnamaldehyde at 0.06% inactivated Salmonella completely after 24 h in water with 1% feces at both temperatures. In water containing 1% feed, TC (0.06%) reduced S. Enteritidis to undetectable levels after 3 d at 12.5°C or 7 d at 25°C. Presence of feed or feces in water reduced the antibacterial effect (P < 0.001) of TC. The effect of TC on C. jejuni was more pronounced than that on S. Enteritidis. The TC at 0.06% completely inactivated the pathogen after 1 d of incubation at both temperatures. The presence of feces or feed did not have any effect (P > 0.001) on the antibacterial property of TC on C. jejuni. Results indicate that TC is effective in killing S. Enteritidis and C. jejuni in chicken drinking water and may decrease the likelihood that water will contribute to colonization of chickens by these pathogens.     

Assessment of attenuated Salmonella vaccine strains in controlling experimental Salmonella Typhimurium infection in chickens

Salmonella hold considerable promise as vaccine delivery vectors for heterologous antigens in chickens. Such vaccines have the potential additional benefit of also controlling Salmonella infection in immunized birds. As a way of selecting attenuated strains with optimal immunogenic potential as antigen delivery vectors, this study screened 20 novel Salmonella Typhimurium vaccine strains, differing in mutations associated with delayed antigen synthesis and delayed attenuation, for their efficacy in controlling colonization by virulent Salmonella Typhimurium, as well as for their persistence in the intestine and the spleen. Marked differences were observed between strains in these characteristics, which provide the basis for selection for further study as vaccine vectors.     

Introduction: Reducing Salmonella Enteritidis contamination of shell eggs

Salmonella Enteritidis is a leading food-borne pathogen in the United States, with many outbreaks in humans traced back to shell eggs. As a result, the implementation of effective strategies for reducing Salmonella Enteritidis in commercial layer flocks has become a critical public health and economic objective. In this paper, we share the findings of 2 multistate USDA-National Integrated Food Safety Initiative grant teams and their work aimed at Salmonella Enteritidis reduction in shell eggs. One project, led by K. Venkitanarayanan, is using plant-derived antimicrobial molecules as dietary supplements to reduce Salmonella Enteritidis colonization of the digestive and reproductive tract of chickens. The same molecules are being evaluated for their effect on Salmonella Enteritidis in egg wash solutions. The project led by S. Kariyawasam used on-farm investigation and novel bacterial typing methods to study Salmonella Enteritidis transmission in diverse layer environments to update and optimize Egg Quality Assurance Programs that will significantly reduce Salmonella Enteritidis contamination of shell eggs. The current US Food and Drug Administration Egg Safety Rule and Egg Quality Assurance Programs are based on critical control points and best management practices developed from studies of large flocks (>50,000 hens) conducted in the 1990s, indicating that opportunities exist to improve preharvest programs to reduce Salmonella Enteritidis contamination. This paper will share the findings of these 2 projects.     

Salmonella Incidence in Broilers from Breeders Vaccinated with Live and Killed Salmonella

Salmonella reduction in broilers from commercial broiler breeders vaccinated with live and killed Salmonella vaccines was evaluated. Broiler breeders were vaccinated with Poulvac ST live Salmonella Typhimurium vaccine at 1 d of age, and this was repeated at 2 and 6 wk of age. The breeders were then administered a killed autogenous oil emulsion adjuvanted vaccine containing Salmonella Kentucky, Salmonella Heidelberg, and Salmonella Hadar, at 10 and 18 wk of age. From the ages of 36 to 52 wk, eggs from the breeder flock were hatched, and progeny were challenged in 4 separate experiments at 1 d of age by oral gavage with 1 × 10⁶ cfu/chick by either Salmonella Kentucky, Salmonella Heidelberg, Salmonella Hadar, or Salmonella Enteritidis, each containing resistance to naladixic acid at 32 μg/mL. At 17 to 21 d of age, the broilers were euthanized, and 1 side of the cecum was cultured for Salmonella, and the other side of the cecum was used for enumeration on positive samples. Recovered Salmonella was confirmed to be the challenge strain by O-antisera grouping. This study indicated a difference in Salmonella incidence and enumeration between the vaccinated and nonvaccinated breeder groups for certain species. When challenged with serotypes Salmonella Kentucky, Salmonella Hadar, and Salmonella Heidelberg, protection was noted with a reduction of 28, 17, and 11%, respectively, when compared with the control groups. However, protection was not seen when challenged with S. enteritidis. Under the conditions of this study, live and killed vaccination of commercial broiler breeders with Salmonella contributes protection to progeny when challenged at 1 d of age.     

Transmission and genetic diversity of Enterococcus faecalis among layer chickens during hatch

Background

Studies on transmission of Enterococcus faecalis among chickens during hatch have not been carried out so far. Information about vertical transmission and subsequent spreading and colonization of the cloacal mucosa through cloacal ''drinking'' during hatch are important to understand the epidemiology of E. faecalis infections. In the present investigation vertical transmission and subsequent spreading and colonization of the cloacal mucosa of chickens by E. faecalis through cloacal ''drinking'' were examined.

Methods

Two different batches of layer chickens originating from 45 weeks old Brown and White Lohmann parents, respectively from the same farm were sampled in the hatcher. Isolates were confirmed to be E. faecalis by polymerase chain reaction (PCR) and further by multilocus sequence typing (MLST) to state their population structure and comparison made to sequence types previously obtained from chicken.

Results

A total of 480 chickens were swabbed from the cloacae just after hatch and after 24 hours. A total of 101 isolates were confirmed as E. faecalis by a species specific PCR. The prevalence of E. faecalis increased from 14% at 0 h to 97% after 24 h for the Brown Lohmann chickens and from 0.5% to 23% for the White Lohmann flock. The 84 isolates analysed by MLST were distributed on 14 sequence types (ST). Three ST (401, 82 and 249) accounted for 64% of all isolates analysed by MLST after 24 h. ST 82 has previously been reported from amyloid arthropathy and other lesions in poultry.

Conclusions

The present findings demonstrated a high potential of a few contaminated eggs or embryos to rapidly facilitate the spread of E. faecalis to almost all chickens during hatch.     

Routes of transmission of Salmonella and Campylobacter in breeder turkeys

Salmonella and Campylobacter are frequent colonizers of the intestinal tracts of poultry and have often been associated with human foodborne illness. The entry, transmission, and prevalence of both pathogens have been extensively studied in chickens but little information is available for turkeys. This project monitored turkey breeder hens and toms from d of hatch to 65 wk of age with the objective of determining routes of transmission for Salmonella and Campylobacter throughout the turkey production cycle. Breeder poults were separated by sex and then into 2 groups (control and inoculated) for each sex. The inoculated group was orally gavaged with marker strains of both Salmonella and Campylobacter. The inoculated groups (toms and hens) were placed on the opposite side of a growout house from the uninoculated groups. Fecal samples, intestinal samples and organs, feed, drinkers, and potential vectors such as insects and mice, were analyzed at different times until 65 wk. Monitoring showed that Campylobacter spread rapidly and cross-contaminated turkeys throughout the growout house. For both Salmonella and Campylobacter, naturally occurring strains that were first isolated in control groups at wk 3 and 4, respectively, outcompeted marker strains several wk post inoculation and persisted in the flock. The most common naturally occurring strains were C. jejuni (tetracycline resistant), C. coli (kanamycin resistant), and S. Agona. Campylobacter and Salmonella also were isolated from flies and from a mouse, confirming the importance of proper pest control and biosecurity to reduce the spread of the bacteria.     

Salmonella enterica Typhimurium infection causes metabolic changes in chicken muscle involving AMPK,fatty acid and insulin/mTOR signaling

Salmonella enterica serovar Typhimurium (Salmonella Typhimurium) infection of chickens that are more than a few days old results in asymptomatic cecal colonization with persistent shedding of bacteria. We hypothesized that while the bacterium colonizes and persists locally in the cecum it has systemic effects, including changes to metabolic pathways of skeletal muscle, influencing the physiology of the avian host. Using species-specific peptide arrays to perform kinome analysis on metabolic signaling pathways in skeletal muscle of Salmonella Typhimurium infected chickens, we have observed key metabolic changes that affected fatty acid and glucose metabolism through the 5''-adenosine monophosphate-activated protein kinase (AMPK) and the insulin/mammalian target of rapamycin (mTOR) signaling pathway. Over a three week time course of infection, we observed changes in the phosphorylation state of the AMPK protein, and proteins up and down the pathway. In addition, changes to a large subset of the protein intermediates of the insulin/mTOR pathway in the skeletal muscle were altered by infection. These changes occur in pathways with direct effects on fatty acid and glucose metabolism. This is the first report of significant cellular metabolic changes occurring systemically in chicken due to a Salmonella infection. These results have implications not only for animal production and health but also for the understanding of how Salmonella infection in the intestine can have widespread, systemic effects on the metabolism of chickens without disease-like symptoms.     

Determination of Ileum Microbial Diversity of Broilers Fed Triticale- or Corn-Based Diets and Colonized by Salmonella

Diversity of the bacterial communities in the ileum of broilers was characterized using denaturing gradient gel electrophoresis. Denaturing gradient gel electrophoresis separation of polymerase chain reaction amplicons of the V2–V3 variable regions of the 16S rDNA is a common method to profile community diversity and has been used to assess the effects of diet and antibiotics on the ileal bacterial community of chickens. Broilers raised either on litter floor or in cage batteries were fed either a finely ground corn- (control), a finely ground triticale-, or a whole triticale-based diet from 0 to 42 d. Microbial DNA was extracted from the ileum content of 42-d-old broilers, and the 16S rDNA gene was amplified by polymerase chain reaction and the amplicons separated by denaturing gradient gel electrophoresis. Diversity indexes including richness, evenness, diversity, and pairwise similarity coefficients were calculated. Diversity indexes were related to the dietary treatments, housing designs, and to changes in Salmonella colonization of broiler ceca as characterized by the most probable number method. Higher microbial diversity indexes were observed among birds fed whole triticale-based diets and reared on litter floors. In contrast, finely ground grain treatments had lower diversity and higher Salmonella prevalence than the whole triticale treatment. The data indicated that combination of high dietary fiber content and increased coarseness of the diet by feeding whole triticale stimulated microbial community diversity and discouraged Salmonella colonization, perhaps through a competitive exclusion-type mechanism.     

Cross-protection against Salmonella Typhimurium infection conferred by a live attenuated Salmonella Enteritidis vaccine

In this study, a genetically engineered live attenuated Salmonella Enteritidis (SE) vaccine was evaluated for its ability to protect against Salmonella Typhimurium (ST) infection in chickens. The birds were orally primed with the vaccine on the 1st day of life and given an oral booster at 5 wk of age. Control birds were orally inoculated with phosphate-buffered saline. Both groups of birds were orally challenged with a virulent ST strain at 9 wk of age. Compared with the control chickens, the vaccinated chickens had significantly higher levels of systemic IgG and mucosal IgA against specific ST antigens and a significantly greater lymphoproliferative response to ST antigens. The excretion of ST into the feces was significantly lower in the vaccinated group than in the control group on days 9 and 13 d after challenge. In addition, the vaccinated group had significantly fewer pronounced gross lesions in the liver and spleen and lower bacterial counts in the internal organs than the control group after challenge. These data indicate that genetically engineered live attenuated SE may induce humoral and cellular immune responses against ST antigens and may confer protection against virulent ST challenge.     

In ovo leptin administration affects hepatic lipid metabolism and microRNA expression in newly hatched broiler chickens

Background: A leptin-like immunoreactive substance has been found in chicken eggs and has been implicated in serving as a maternal signal to program offspring growth and metabolism. In the present study, we investigated the effects of in ovo leptin administration on hatch weight, serum and hepatic concentrations of metabolites and hormones, as well as on the expression of genes involved in hepatic lipid metabolism and the predicted microRNAs (miRNAs) targeting the affected genes. To this end we injected fertile eggs with either 0.5 μg of recombinant murine leptin or vehicle (PBS) before incubation. Results: Prenatally leptin-exposed chicks showed lower hatch weight, but higher liver weight relative to the body weight, compared to the control group. In ovo leptin treatment increased the hepatic content and serum concentration of leptin in newly hatched chickens. The hepatic contents of triglycerides (TG) and total cholesterol (Tch) were decreased, whereas the serum levels of TG, Tch and apolipoprotein B (ApoB) were increased. The hepatic mRNA expression of sterol regulator element binding protein 1 (SREBP-1c), SREBP-2, hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and cholesterol 7α-hydroxylase 1 (CYP7A1) was significantly up-regulated, as was the protein content of both SREBP-1c and SREBP-2 in hepatic nuclear extracts of leptin-treated chickens. Moreover, out of 12 miRNAs targeting SREBP-1c and/or HMGCR, five were significantly up-regulated in liver of leptin-treated chicks, including gga-miR-200b and gga-miR-429, which target both SREBP-1c and HMGCR. Conclusions: These results suggest that leptin in ovo decreases hatch weight, and modifies hepatic leptin secretion and lipid metabolism in newly hatched broiler chickens, possibly via microRNA-mediated gene regulation.     

Evaluation of recovery of Salmonella from trachea and ceca in commercial poultry

Unpublished data from our laboratory suggest that the respiratory tract may be a viable portal of entry for Salmonella infection. Further, field reports have indicated that tracheal sampling can be a sensitive tool for monitoring for Salmonella incidence in commercial flocks. In the present study we conducted a series of field trials in North and South America to evaluate the association between cecal and tracheal recovery of Salmonella in chickens and turkeys from commercial flocks. Environmental humidity and temperature were measured to evaluate their effects on frequency of isolation from the organs. Salmonella was recovered from tracheal samples in all trials. In 3 of the 4 trials in which both trachea and ceca were sampled, the incidence of Salmonella recovery was higher in tracheal samples. Though Salmonella was not recovered from ceca in trial 2, 5% of liver and spleen samples indicated infection. Environmental conditions were not associated with incidence of Salmonella recovery. These data suggest that tracheal contamination can be a good indicator of Salmonella infection under commercial poultry conditions.     

The consequence of low mannose-binding lectin plasma concentration in relation to susceptibility to Salmonella Infantis in chickens

Mannose-binding lectin (MBL) is a key protein in innate immunity. MBL binds to carbohydrates on the surface of pathogens, where it initiates complement activation via the lectin-dependent pathway or facilitates opsonophagocytosis. In vitro studies have shown that human MBL is able to bind to Salmonella, but knowledge in relation to chicken MBL and Salmonella is lacking. In order to study this relation day-old chickens from two selected lines L10H and L10L, differing in MBL serum concentration, were either orally infected with S. Infantis (S.123443) or kept as non-infected controls. The differences between healthy L10H and L10L chicken sublines were more profound than differences caused by the S. Infantis infection. The average daily body weight was higher for L10H than for L10L, regardless of infection, indicating beneficial effects of MBL selection on growth. Salmonella was detected in cloacal swabs and the number of Salmonella positive chickens during the experiment was significantly higher in L10L than L10H, indicating that MBL may affect the magnitude of Salmonella colonisation in day-old chickens. MBL expression was determined in ceca tissue by real-time RT-PCR. L10H chickens showed a significantly higher relative expression than L10L at days 1 and 41 pi, regardless of infection. Finally, flow cytometric analysis of whole blood from infected chickens showed that L10H had a significantly higher count of all assessed leucocyte subsets on day 5 pi, and also a higher count of monocytes on day 12 pi than L10L. No difference was observed between infected and non-infected L10L chicken.