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1.
Salmonella enterica serovar Choleraesuis (Salmonella Choleraesuis) causes a lethal systemic infection (salmonellosis) in swine. Live attenuated Salmonella Choleraesuis vaccines are effective in preventing the disease, and isolates of Salmonella Choleraesuis with mutations in the cAMP-receptor protein (CRP) gene (Salmonella Choleraesuis ∆crp) are the most widely used, although the basis of the attenuation remains unclear. The objective of this study was to determine if the attenuated phenotype of Salmonella Choleraesuis ∆crp was due to alterations in susceptibility to gastrointestinal factors such as pH and bile salts, ability to colonize or invade the intestine, or cytotoxicity for macrophages. Compared with the parental strain, the survival rate of Salmonella Choleraesuis ∆crp at low pH or in the presence of bile salts was higher, while the ability of the mutant to invade intestinal epithelia was significantly decreased. In examining the role of CRP on the secretory function of the Salmonella pathogenicity island 1 (SPI-1) encoded type III secretion system (T3SS), it was shown that Salmonella Choleraesuis ∆crp was unable to secrete the SPI-1 T3SS effector proteins, SopB and SipB, which play a role in Salmonella intestinal invasiveness and macrophage cytotoxicity, respectively. In addition, caspase-1 dependent cytotoxicity for macrophages was significantly reduced in Salmonella Choleraesuis ∆crp. Collectively, this study demonstrates that the CRP affects the secretory function of SPI-1 T3SS and the resulting ability to invade the host intestinal epithelium, which is a critical element in the pathogenesis of Salmonella Choleraesuis.  相似文献   

2.
Salmonella Gallinarum biovar Pullorum (S. Gallinarum biovar Pullorum) is the causative agent of pullorum disease (PD) in chickens which results in considerable economic losses to the poultry industries in developing countries. PCR-Signature Tagged Mutagenesis was used to identify virulence determinants of S. Gallinarum biovar Pullorum and novel attenuated live vaccine candidates for use against this disease. A library of 1800 signature-tagged S. Gallinarum biovar Pullorum mutants was constructed and screened for virulence-associated genes in chickens. The attenuation of 10 mutants was confirmed by in vivo and in vitro competitive index (CI) studies. The transposons were found to be located in SPI-1 (2/10 mutants), SPI-2 (3/10), the virulence plasmid (1/10) and non-SPI genes (4/10). One highly attenuated spiC mutant persisted in spleen and liver for less than 10 days and induced high levels of circulating antibody and protective immunity against oral challenge in young broiler chickens. The spiC mutant is a potential new vaccine candidate for use with chickens against this disease.  相似文献   

3.
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.  相似文献   

4.
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5.
Salmonella Typhimurium strain expressing the Actinobacillus pleuropneumoniae antigens, ApxIA, ApxIIA, ApxIIIA and OmpA, was previously constructed as a vaccine candidate for porcine pleuropneumonia. This strain was a live attenuated (∆lon∆cpxR∆asd)Salmonella as a delivery host and contained a vector containing asd. An immunological study of lymphocyte proliferation, T-lymphocyte subsets and cytokines in the splenocytes of a mouse model was carried out after stimulation with the candidate Salmonella Typhimurium by intranasal inoculation. The splenic lymphocyte proliferation and the levels of IL-4, IL-6 and IL-12 of the inoculated mice were significantly increased, and the T- and B-cell populations were also elevated. Collectively, the candidate may efficiently induce the Th1- and Th2-type immune responses.  相似文献   

6.
Using a deletion mutant in the regulator of SPI-2, ssrA, we investigated the role of SPI-2 in invasion, intestinal colonization and reproductive tract infection of chickens by Salmonella Enteritidis. The ssrA mutant was fully invasive in phagocytic and non-phagocytic cells but failed to persist within chicken macrophages. The ability of Salmonella Enteritidis to cause disease in orally infected 1-day-old chicks was not altered when ssrA was deleted. Furthermore, caecal colonization was not affected, while spleen and liver showed reduced colonization. Following intra-peritoneal and intravenous infection of 1-day-old chicks, internal organ colonization was strongly reduced. After intravenous inoculation in adult laying hens bacterial numbers of the ssrA mutant were significantly lower in oviducts and ovaries as compared to the wild type strain. The chickens showed less reproductive tract lesions and the recovery of egg production were faster compared to the wild type strain infected chickens. These findings indicate that the SPI-2 regulator ssrA promotes reproductive tract colonization, but is not essential for intestinal colonization of chickens with the host non-specific serotype Enteritidis.  相似文献   

7.
Competitive exclusion (CE) cultures, given as a single dose on the day of hatch, together with good hygienic practices has been shown to be a novel approach to control Salmonella in poultry. The ability of the CE product Broilact and 2 probiotics, FloraMax-B11 and Colostrum, to prevent Salmonella colonization in newly hatched chickens was evaluated employing a slightly modified Mead-model chicken assay. In a parallel study the effect of the 3 treatments on the production of volatile fatty acids in the ceca were determined. In the Salmonella study 2 separate experiments were done. In the first experiment all 3 treatment materials were given as a single dose on d 1. In the second experiment, which consisted only of Broilact and FloraMax-B11, the latter was given in the drinking water during the 3 first d after hatch. In both experiments the chicks were challenged with Salmonella enterica serovar Infantis on d 2. The results of the present study show that Broilact was superior to the 2 other treatment materials in protecting the newly hatched chickens against Salmonella colonization. The parallel study showed only minor differences among the different treatments. Based on the results of the Salmonella challenge study, it was concluded that Broilact was the only treatment material that was established in the gut of the newly hatched chickens in such a way that the colonization of Salmonella was prohibited.  相似文献   

8.
Salmonella enterica Gallinarum (SG) causes fowl typhoid (FT), a septicemic disease in avian species. We constructed deletion mutants lacking the stress sigma factor RpoS, the nitric oxide (NO)-detoxifying flavohemoglobin Hmp, and the SsrA/SsrB regulator to confirm the functions of these factors in SG. All gene products were fully functional in wild-type (WT) SG whereas mutants harboring single mutations or a combination of rpoS, hmp, and ssrAB mutations showed hypersusceptibility to H2O2, loss of NO metabolism, and absence of Salmonella pathogenicity island (SPI)-2 expression, respectively. A triple-deletion mutant, SGΔ3 (SGΔrpoSΔhmpΔssrAB), was evaluated for attenuated virulence and protection efficacy in two-week-old Lohmann layer chickens. The SGΔ3 mutant did not cause any mortality after inoculation with either 1 × 106 or 1 × 108 colony-forming units (CFUs) of bacteria. Significantly lower numbers of salmonellae were recovered from the liver and spleen of chickens inoculated with the SGΔ3 mutant compared to chickens inoculated with WT SG. Vaccination with the SGΔ3 mutant conferred complete protection against challenge with virulent SG on the chickens comparable to the group vaccinated with a conventional vaccine strain, SG9R. Overall, these results indicate that SGΔ3 could be a promising candidate for a live Salmonella vaccine against FT.  相似文献   

9.
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.  相似文献   

10.
Salmonella enterica serovars Typhimurium, Enteritidis, Dublin, Choleraesuis or Gallinarum can colonise liver and spleen in particular hosts while infections with serovars Infantis, Agona, Hadar, etc. are usually limited to gastrointestinal tract. Reasons for this behavior are unknown, although it has been shown that sodCI and spv genes exhibit a strict distribution between more and less virulent serovars and they influence Salmonella virulence. However to what extent the presence or absence of these genes is associated with the increased virulence of serovars which possess them has never been addressed experimentally. In this study we therefore first confirmed the exclusive association of spvB and sodCI genes with the former group of serovars. In the next step we removed these two genes from S. Enteritidis genome and compared the virulence of such a mutant with the virulence of S. Infantis, S. Agona and S. Hadar for chickens and highly sensitive Balb/C mice. Single strain infection showed that the deletion of these two genes from S. Enteritidis resulted in the reduction of its virulence for mice but not for chickens. Mixed infection further confirmed these observations and indicated that in mice but not in chickens the virulence of sodCI and spv mutant was reduced to the natural virulence of serovars Infantis, Agona and Hadar. Although sodCI and spv genes do not influence S. Enteritidis virulence for chickens directly, they may be of an indirect effect through the increased persistence of S. Enteritidis in mice and increased probability of the reintroduction of S. Enteritidis into poultry flocks.  相似文献   

11.
A live attenuated Salmonella enterica serovar Montevideo (SM) mutant JOL1599 was constructed by deletion of virulence-associated genes. The protective efficacy and immune response profiles of chickens immunized with JOL1599 were investigated. Immunized chickens demonstrated significant increases in plasma IgG and lymphocyte proliferative responses (P ≤ 0.05). Increased levels of IL-6, INF-γ, and IL-12 were also observed. Immunized birds strongly responded to infection by rapid stimulation of a CD4+ subset of T cells. Organ bacterial recovery assay revealed a significant reduction in the challenge strain among immunized birds. Multiple doses of JOL1599 enhanced the immune responses of the birds as revealed by ascending trends of the immunological profiles. These findings indicate that immunization of chickens with JOL1599 may provide protection against Salmonella Montevideo infection via induction of IL-6, INF-γ, and IL-12 protective cytokines, which in turn triggers conducive humoral and cell-mediated immune responses.  相似文献   

12.
Salmonella Enteritidis in contaminated eggs is a public health hazard that may cause hospitalization or death in the elderly, infants, and individuals with impaired immune systems. Prevention of Salmonella Enteritidis infection of laying hens is an essential first step in reducing Salmonella Enteritidis outbreaks in humans. Multiple interventions at several stages during egg production can combine to reduce numbers of infected chickens and keep egg contamination to low levels. Every effort should be made to exclude Salmonella Enteritidis from egg production premises by implementing effective biosecurity measures, stocking the farm with Salmonella Enteritidis-free replacement pullets, controlling rodent and insect vectors, and denying wild birds and pets access to chicken houses. Diligent cleaning and disinfection of chicken houses before introduction of a new flock will minimize environmental exposure and indirect horizontal transmission of multiple pathogens, including Salmonella Enteritidis. Increased resistance of chickens to intestinal colonization by Salmonella Enteritidis can be attained by the use of probiotics, prebiotics, and synbiotics. Laying hens should be immunized with live and killed vaccines to stimulate mucosal and systemic immunity and reduce the prevalence of Salmonella Enteritidis-contaminated eggs. Shell eggs should be refrigerated as soon as possible after laying to keep Salmonella Enteritidis cells at low levels in any contaminated eggs. Comprehensive Salmonella Enteritidis-control programs have proven to be successful in reducing the incidence of Salmonella Enteritidis infections in both egg-laying flocks and humans.  相似文献   

13.

Background

The Swedish Salmonella control program has been running for decades and has resulted in a low prevalence of Salmonella in Swedish food producing animals. Routine bacteriology is used to detect Salmonella, however, bacteriology is time consuming, costly and has a low sensitivity. Different enzyme-linked immunosorbent assays (ELISAs) have been developed for detection of antibodies against Salmonella Dublin and S. Typhimurium in bovine bulk milk, individual milk samples as well as in sera. Screening bulk milk for antibodies against Salmonella spp. could improve the cost-effectiveness of the surveillance in Swedish dairy cattle, but as characteristics of tests may vary in different populations, tests should always be evaluated in the specific population where they will be used. Hence, the aim of this study was to evaluate the specificities of three bovine ELISAs when used to analyse bulk milk samples from Swedish dairy cattle. A second aim was to compare the performance of the two Dublin ELISAs tested.

Methods

Bulk milk samples for analysis were randomly selected from samples collected within the Swedish bulk milk sampling scheme and analyzed with the three ELISAs; a Danish in-house Dublin ELISA, PrioCHECK® Salmonella Ab bovine Dublin ELISA and PrioCHECK® Salmonella Ab bovine ELISA (hereafter named mixed ELISA). The specificities of the ELISAs were calculated assuming a disease-free status in Sweden i.e. that all test positive samples were assumed to be false positive results. This assumption can be used when a disease is known to be infrequent.

Results

The calculated specificities of the two Dublin ELISAs and the mixed ELISA, when using the producer’s recommended cut-off value of the corrected optic-density percent (ODC%) were 99.4% (95% Confidence Interval (CI): 98.8% -99.8%), 99.4% (95% CI: 98.8% -99.8%) and 97.9% (95% CI: 96.8% -98.7%), respectively. The correlation between the ODC% values of the two Dublin ELISAs was 0.83.

Conclusions

We conclude that the evaluated ELISAs have sufficiently high specificities to be used as supplement to bacteriological examinations in the Swedish Salmonella control program in cattle as well as a primary screening test in routine surveillance for S. Dublin.  相似文献   

14.
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15.
The purpose of this study was to evaluate the capacity of a lactic acid bacteria (LAB) inoculum to protect calves with or without lactose supplements against Salmonella Dublin infection by evaluating histopathological lesions and pathogen translocation. Fifteen calves were divided into three groups [control group (C-G), a group inoculated with LAB (LAB-G), and a group inoculated with LAB and given lactose supplements (L-LAB-G)] with five, six, and four animals, respectively. The inoculum, composed of Lactobacillus (L.) casei DSPV 318T, L. salivarius DSPV 315T, and Pediococcus acidilactici DSPV 006T, was administered with milk replacer. The LAB-G and L-LAB-G received a daily dose of 109 CFU/kg body weight of each strain throughout the experiment. Lactose was provided to the L-LAB-G in doses of 100 g/day. Salmonella Dublin (2 × 1010 CFU) was orally administered to all animals on day 11 of the experiment. The microscopic lesion index values in target organs were 83%, 70%, and 64.3% (p < 0.05) for the C-G, LAB-G, and L-LAB-G, respectively. Administration of the probiotic inoculum was not fully effective against infection caused by Salmonella. Although probiotic treatment was unable to delay the arrival of pathogen to target organs, it was evident that the inoculum altered the response of animals against pathogen infection.  相似文献   

16.
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.  相似文献   

17.
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18.
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.  相似文献   

19.
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.  相似文献   

20.
Salmonella enterica serovar Typhimurium is an animal and zoonotic pathogen of worldwide importance. In pigs, transport and social stress are associated with reactivation and spread of Salmonella Typhimurium infection. The stress-related catecholamine norepinephrine (NE) has been reported to activate growth and virulence factor expression in Salmonella; however the extent to which NE contributes to stress-associated salmonellosis is unclear. We studied the impact of releasing NE from endogenous stores during Salmonella Typhimurium infection of pigs by administration of 6-hydroxydopamine (6-OHDA), which selectively destroys noradrenergic nerve terminals. Treatment of pigs with 6-OHDA 7 or 16 days post-oral inoculation with Salmonella Typhimurium produced elevated plasma NE levels and transiently, but significantly, increased faecal excretion of the challenge strain. Oral administration of NE to Salmonella Typhimurium-infected pigs also transiently and significantly increased shedding; however pre-culture of the bacteria with NE did not alter the outcome of infection. Salmonella has been proposed to sense and respond to NE via a homologue of the adrenergic sensor kinase QseC. A ΔqseC mutant of Salmonella Typhimurium was consistently excreted in lower numbers than the parent strain post-oral inoculation of pigs, though not significantly so. 6-OHDA treatment of pigs infected with the ΔqseC mutant also increased faecal excretion of the mutant strain, albeit to a lesser extent than observed upon 6-OHDA treatment of pigs infected with the parent strain. Our data support the notion that stress-related catecholamines modulate the interaction of enteric bacterial pathogens with their hosts.  相似文献   

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