Secretion of Salmonella-specific antibodies in the oviducts of hens experimentally infected with Salmonella enteritidis

Effect of feeding chitosan and blend of essential organic acids on growth performance, haematological parameters and innate immunity in early aged male layer chicks

The use of antibiotics as conventional feed additives in poultry operations have proven useful, however resulted serious health concerns to consumer due to their bio-accumulation, besides rising problem of antimicrobial resistance in microbes, thus, an alternative to antibiotic growth promoter have called for. One of the aim of the experiment was to assess the lone and combined effects of feeding of chitosan oligosaccharide (COS) and blend of organic acids and short chain fatty acids in essential oils on growth performance, haematological parameters, relative lymphoid organ weight and innate immunity in early aged layer chick (male birds). A total of ninety, day-old chicks were randomly allotted into five groups: CO, Control group fed only poultry feed ; AGP, antibiotic growth promoter fed Avilomycin at the dose of 200 mg/kg of poultry feed; CH, chitosan oligosaccharide fed at the rate of 100 mg/kg feed; OE, blend of organic acids and short chain fatty acids in essential oils contained 1000 to 2000 mg/kg feed in a graded dose per week and CH + OE, chitosan oligosaccharide plus blend of organic acids and short chain fatty acids in essential oils at consistent rate and manner as followed for each of given feed additives when fed individually. Data on growth performance, samples for haematological parameters and innate immunity were measured and assayed on 7th, 21st and 42nd day post feeding (dpf) respectively. The results showed that compared with the control group; there is a marginal gain in body weight at 7th and 21st dpf in CH group and the corresponding CH + OE group. Feed conversion ratio in CH group was remarkably good at 7th and 21st dpf. No significant difference was observed in relative organ weights of thymus, spleen and Bursa of Fabricius in treatment groups as compared to control birds; however a significant rise in splenic weight index in OE fed birds at 42nd dpf noted. Haematological changes were inconsequential in treatment groups with an exception to enhancement of heterophil to lymphocyte ratio (H:L ratio) in CH group at 42nd dpf. Serum lysozyme activity proportionately elevated in CH + OE group on 21st and 42nd dpf when measured against control group; on the other hand no detectable augmentation of gut lysozyme activity observed. Both serum bactericidal and gut bactericidal activity boosted in combinatorial group at 42nd dpf. These results indicated that early age feeding of chitosan individually or combination with organic acids and short chain fatty acids in layer chick is beneficial, as it has the potential to enhance body weight gain to some extent and improves systemic and localized innate immunity to offer protection against infectious assaults thus may avoid early chick mortality in farms.

Induction of Mucosal Humoral Immunity by Subcutaneous Injection of an Oil-emulsion Vaccine against Salmonella enterica subsp. enterica serovar Enteritidis in Chickens

Salmonella enterica subsp. enterica serovar Enteritidis (SE) is one of the major causes of food poisoning. Much effort has been made to develop a vaccine for the prevention of SE colonization and infection in poultry. However, the effect of inactivated whole-cell SE vaccines on the bacterial attachment has not been clarified. This study investigated the immune responses to a killed whole-cell SE vaccine in chickens and the effect of vaccination on the bacterial attachment of SE to cultured Vero cells. A 1 ml dose of 10⁸–10⁹ CFU viable SE bacterial cells was orally administered to chickens at 4 weeks or 10 months post vaccination. The number (CFU) of SE in 1 g of cecal droppings was counted on day 6 after administration. The SE CFUs were significantly lower (p < 0.05) in the vaccinated chickens, not only at 4 weeks but also at 10 months after vaccination, than in the unvaccinated control chickens. Anti-SE IgG and anti-SE IgA were detected using enzyme-linked immunosorbent assay (ELISA) in serum and intestinal and oviduct fluid samples from vaccinated chickens. Adhesion of heat-killed SE cells to Vero cells was reduced by pre-treatment of the bacteria by the vaccinated chicken-derived intestinal fluid, indicating the potential of the vaccine-induced antibody to prevent SE adhesion to epithelial cell surfaces.

The enhanced immune responses induced by Salmonella enteritidis ghosts loaded with Neisseria gonorrhoeae porB against Salmonella in mice

Human health has been seriously endangered by highly prevalent salmonellosis and multidrug-resistant Salmonella strains. Current vaccines suffer from variable immune-protective effects, so more effective ones are needed to control Salmonella infection : Bacterial ghosts have been produced by the expression of lysis gene E from bacteriophage PhiX174 and can be filled with considerable exogenous substances such as DNA or drugs as a novel platform. In this study, Salmonella enteritidis (SE) ghosts were developed and loaded with Neisseria gonorrhoeae porin B (porB) to construct a novel inactive vaccine. Our new studies show that SE ghosts loaded with porB displayed increased production of pro-inflammatory cytokines (IL-1β, IL-6, IL-10 and IL-12p70) in bone marrow-derived dendritic cells (BMDCs), and elicited significantly higher specific systemic and mucosal immune responses to Salmonella than SE ghosts alone. In addition, the novel porB-loaded ghosts conferred higher protective effects on virulent Salmonella challenge. For the first time, we demonstrate that N. gonorrhoeae porB, as a novel adjuvant, can increase the immunogenicity of SE ghosts. Our studies suggested that Salmonella enteritidis ghosts loaded with Neisseria gonorrhoeae porin B might be a useful mucosal Salmonella vaccine candidate for practical use in the future.

Physiology, pathogenicity and immunogenicity of live, attenuated Salmonella enterica serovar Enteritidis mutants in chicks

To construct a novel live, attenuated Salmonella vaccine, the lon, cpxR and cpdB genes were deleted from a wild-type Salmonella enterica serovar Enteritidis-6 (SM-6) strain using the phage λ Red homologous recombination system, resulting in SM-△CpxR, SM-△C/Lon and SM-△C/L/CpdB. The growth curves of strain SM-△C/Lon grew more rapidly than the other strains and had OD 600 values higher than the other strains starting at the 4 h time point. The growth curves of strain SM-△C/L/CpdB were relatively flat. The colonization time of SM-△C/L/CpdB is about 8-10 days. Deleting the lon/cpxR/cpdB (SM-6) genes resulted in an approximate 10(3)-fold attenuation in virulence assessed by the analysis of the LD50 of specific pathogen-free (SPF) chicks. This result indicated that the deletion of the lon, cpxR and cpdB genes induced significant virulence attenuation. The protective effects of SM-△C/L/CpdB vaccination in SPF chicks against 5 × 10(9) colony forming units (CFU) of S. Enteritidis were resulted from the induction of an effective immune response. These findings demonstrate the potential of mutant SM-△C/L/CpdB to be used as an effective vaccine.

An immunogenic Salmonella ghost confers protection against internal organ colonization and egg contamination

The tightly regulated expression of the PhiX174 lysis gene E from a multi-copy plasmid led to the stable production of an Salmonella Enteritidis bacterial ghost. The present study was conducted to evaluate induction of the humoral and cell-mediated immune responses induced after single or double intramuscular immunization with the S. Enteritidis ghost and to assess its protective effect on colonization of the intestinal tract, visceral and reproductive organs, internal egg contamination, and egg production of laying chickens. A total of 60 chickens were equally divided into three groups (n=20); group A (non-immunized control), group B (immunized at 8 and 16 weeks of age) and group C (immunized at 16th week of age). Chickens from both immunized groups B and C demonstrated significant increases in plasma IgG, intestinal secretory IgA levels, and antigen-specific lymphocyte proliferative responses. The population of CD3+CD4+ positive T cells in the immunized chickens was also significantly increased after immunization and virulent challenge. In addition, the immunized groups B and C showed significantly higher egg production and a lower percentage of S. Enteritidis contaminated eggs after challenge compared to those of group A. A comparison of challenge strain isolation from the immunized-challenged and non-immunized-challenged layer hens showed that the double immunization group induced excellent protection against intestinal, liver, splenic, and ovarian Salmonella colonization; however, the single immunized chickens showed lower counts only in the splenic and ovarian organs. Overall, the data give compelling evidence that vaccination with the S. Enteritidis ghost induced robust protective immunity against experimental avian salmonellosis and may contribute to the reduce incidence of egg contamination.

Passive protection against Salmonella enterica serovar Enteritidis infection from maternally derived antibodies of hens vaccinated with a ghost vaccine

This study evaluated maternal immunity against Salmonella enterica serovar Enteritidis acquired through the egg yolk. Two-hundred 19-week-old specific pathogen free (SPF) broiler breeders which were randomly divided into two groups of equal size were injected with S. Enteritidis ghosts (5 × 10(9) colony forming units in 0.1 ml per hen) and phosphate-buffered saline (PBS, 0.01 mol ⋅ l(-1), pH 7.4) twice, respectively, with an interval of 2 weeks. An indirect enzyme-linked immunosorbent assay (ELISA) was applied to detect specific antibodies against S. Enteritidis. S. Enteritidis-specific antibody levels in the vaccinated group increased over time and were significantly higher than those of the control group on days 28 (P < 0.001) and 35 (P < 0.001) post-vaccination. Ten 7-day-old chicks from hens that were vaccinated with a S. Enteritidis ghost vaccine were challenged at 14 days of age with 5 × 10(9) CFU of S. Enteritidis DH091 (homologous to the vaccine strain), 8/10 (80%) chicks from vaccinated hens survived, whereas 3/10 (30%) chicks from unvaccinated hens survived. The chicks acquired high levels of serum antibodies against S. Enteritidis. These results reveal that maternal antibodies in chicks acquired from vaccinated hens through eggs can confer a significant protection against S. Enteritidis infection.

Salmonella enteritidis ghost vaccine induces effective protection against lethal challenge in specific-pathogen-free chicks

Bacterial ghosts (BGs) are empty bacterial envelopes generated by expulsion of the bacterial genome and cytoplasmic contents from bacterial cells, and the process is mediated by lysis protein E encoded on bacteriophage PhiX174. BGs represent a new approach in vaccine development and have been applied to a variety of gram-negative bacterial vaccine candidates. In this study, a BG vaccine generated from Salmonella enteritidis (S. enteritidis) strain DH091 was prepared using the highly efficient plasmid, pBV-mE. The efficacy of the BG vaccine was tested using 75 chicks (Gallus gallus) kept under specific pathogen-free (SPF) conditions. A comprehensive evaluation of the immune response, including humoral and cellular immune responses, interferon-γ (IFN-γ) and interleukin-4 (IL-4) production, and histopathology of various tissues, was performed in BG-vaccinated animals subsequently challenged with S. enteritidis. The results were compared with animals that were immunized with the inactivated vaccine. S. enteritidis ghosts not only promoted the generation of high titer antibodies and IFN-γ and IL-4 production but also stimulated a significant increase in CD8(+) and CD4(+) T lymphocytes. In particular, the dramatic increase in CD8(+) T cells indicated that the vaccine was able to induce clearance of intracellular Salmonella. The protective effects of BG vaccination in SPF chicks against 5×10(9) colony forming units of S. enteritidis were a result of the induction of a more effective immune response than that observed with the inactivated vaccine. These findings demonstrate the potential of S. enteritidis ghosts to be used as effective vaccines.

Oxidative and nitrosative responses of the chicken macrophage cell line MQ-NCSU to experimentalSalmonellainfection

Phagocytes limit replication or kill ingested organisms by producing toxic reactive oxygen and nitrogen species via NADPH oxidase and inducible nitric oxide synthase (iNOS). The present experiments were to investigate the production and the possible roles of superoxide, hydrogen peroxide (H2O2) and nitric oxide (NO) in the MQ-NCSU chicken macrophage cell line infected with Salmonella in vitro. After infection, intracellular Salmonella viable counts remained constant until 24 h post infection (PI) and started to decline from 48 h PI. Infection of cells with S. Typhimurium, S. Enteritidis and S. Gallinarum, as well as exposure to S. Enteritidis LPS induced low, but significant concentrations of superoxide 1 to 2 h PI, as determined by reduction of ferricytochrome c. There was no difference in superoxide production in infected cells and control cells after 4 h. Increased H2O2 was observed from cells infected with all the different Salmonella species between 2 and 3 h of infection. Nitrite was always greater in infected cells compared to uninfected cells at all times. However, Salmonella was not completely eliminated from the cells though these cells are capable of eliciting a noticeable oxidative burst response and great nitrosative responses, indicating that a strong oxidative burst (and other mechanism/s) is essential for the elimination of intracellular Salmonella.

Increased lymphocyte subpopulations and macrophages in the ovaries and oviducts of laying hens infected withSalmonella entericaserovar Enteritidis

Salmonella enterica serovar Enteritidis (SE) is a causative agent for human food poisoning cases throughout the world. The ovaries and the oviducts of the laying hens are the major sites of SE colonization from which vertical transmission to eggs occurs. In this study, Salmonella-induced changes in T lymphocytes, B lymphocytes and macrophages in the ovaries and oviducts were assessed after primary and secondary experimental inoculations of laying hen with SE. Statistically significant increases in the numbers of T cells (both CD4+ and CD8+) and macrophages were observed 7 to 14 days after primary inoculation, followed by a peak in B-cell numbers from the 14th day post-primary inoculation onwards in the secretory areas of the oviducts. The peak in lymphocyte numbers immediately preceded a decline in the rate of SE recovery from the reproductive tract beginning at day 14. The correlation of decreased Salmonella recovery with elevated lymphocyte and macrophage numbers strongly suggests that local cell-mediated immunity is involved in controlling SE injection in the ovaries and oviducts.

Oral immunisation of laying hens with the live vaccine strains of TAD Salmonella vac E and TAD Salmonella vac T reduces internal egg contamination with Salmonella Enteritidis

Eggs are a major source of human infections with Salmonella. Therefore controlling egg contamination in laying hen flocks is one of the main targets for control programmes. A study was carried out to assess the effect of oral vaccination with TAD Salmonella vac E, TAD Salmonella vac T and with both vaccines TAD Salmonella vac E and TAD Salmonella vac T, on colonization of the reproductive tract and internal egg contamination of laying hens with Salmonella Enteritidis. Three groups of 30 laying hens were vaccinated at 1 day, 6 weeks and 16 weeks of age with either one of the vaccine strains, or a combination of both vaccine strains, while a fourth group was left unvaccinated. At 24 weeks of age, the birds were intravenously challenged with 0.5 ml containing 5 x 10(7)cfu Salmonella Enteritidis PT4 S1400/94. The number of oviducts from which Salmonella was isolated, was significantly lower in the vaccinated than in the non-vaccinated hens at 3 weeks post-challenge. Significantly less egg contents were Salmonella positive in the birds vaccinated with TAD Salmonella vac E or TAD Salmonella vac T (12/105 batches of eggs in both groups) than in the unvaccinated birds (28/105 batches of eggs). Internal egg contamination in the hens vaccinated with both TAD Salmonella vac E and TAD Salmonella vac T was even more reduced, as over the whole experiment, only one batch of eggs was positive. In conclusion, these data indicate that vaccination of laying hens with these live vaccines could be considered as a valuable tool in controlling internal egg contamination.

Reducing the Carriage of Foodborne Pathogens in Livestock and Poultry

Several foodborne pathogens, including Salmonella species and campylobacters, are common contaminants in poultry and livestock. Typically, these pathogens are carried in the animal's intestinal tract asymptomatically; however, they can be shed in feces in large populations and be transmitted by other vectors from feces to animals, produce, or humans. A wide array of interventions has been developed to reduce the carriage of foodborne pathogens in poultry and livestock, including genetic selection of animals resistant to colonization, treatments to prevent vertical transmission of enteric pathogens, sanitation practices to prevent contamination on the farm and during transportation, elimination of pathogens from feed and water, feed and water additives that create an adverse environment for colonization by the pathogen, and biological treatments that directly or indirectly inactivate the pathogen within the host. To successfully reduce the carriage of foodborne pathogens, it is likely that a combination of intervention strategies will be required.

Cultural and Immunological Detection Methods for Salmonella spp. in Animal Feeds - A Review

Food-borne salmonellosis continues to be a major public health concern, and contamination with Salmonella spp. in pre-harvest animal production is considered a primary contributor to this problem. Animal feeds can easily become contaminated during primary production, feed mixing and processing as well as during feeding. Consequently, monitoring and surveillance of feeds and feed ingredients for Salmonella spp. contamination may be useful or necessary in the prevention and control of this organism. Cultural and immunological detection methods for salmonellae have been used or suggested as possible approaches for use in animal feeds. Cultural methods remain advantageous owing to their ability to detect viable bacterial cells, while immunological methods have the capability of detecting nonculturable bacterial cells. Advancements and improvements in both methodologies offer opportunities for eventual routine use of these detection technologies in animal feed assays.

Tubular Glands of the Isthmus are the Predominant Colonization Site of Salmonella Enteritidis in the Upper Oviduct of Laying Hens

Salmonella enterica serovar Enteritidis is the serovar most frequently isolated from chicken eggs. Colonization of the upper oviduct of hens is believed to play an important role in egg contamination. The interaction of S. enteritidis with gland epithelial cells of the isthmus and the magnum was, therefore, studied in vitro and in vivo. In the first experiment, S. enteritidis bacteria were added to confluent monolayers of primary cultures of chicken tubular epithelial cells of the isthmus (ICTEC) or magnum (MCTEC). Intracellular bacteria in ICTEC and MCTEC were confirmed by a gentamicin protection assay. Internalization in the glandular cells was corroborated by confocal scanning microscopy. Although S. enteritidis was able to invade and proliferate intracellularly during 24 h in the cell culture of both segments, this was significantly more so in the ICTEC. In a second experiment, an in vivo loop model was developed for investigation of the invasiveness of S. enteritidis in the oviduct of laying hens. Loops in the isthmus and magnum of laying hens were made under anaesthesia. S. enteritidis was inoculated into each loop. After 1 h, tubular gland cells were isolated from the infected tissue under gentamicin. S. enteritidis invasiveness was measured as the ratio of isolated bacteria per isolated tubular gland cell. This ratio was higher (P < 0.01) in the isthmus (1.3 x 10(-3)) than in the magnum (5.3 x 10(-5)). In a third experiment, laying hens were intravenously infected with 5 x 10(7) cfu S. enteritidis bacteria. The number of intracellular bacteria was counted in the tubular gland cells of the isthmus and magnum after isolation under gentamicin. The ratio of isolated bacteria per isolated tubular gland cell was again significantly higher in the isthmus as compared with in the magnum. In all 3 assays, the tubular gland cells of the isthmus were more heavily invaded than those of the magnum.