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1.
The superior conservation of antigenic determinants on the surface of genetically inactivated bacterial ghosts makes them attractive immunogenic inactivated vaccine candidates. The efficacy of Salmonella Enteritidis (SE) ghost vaccination was evaluated in chickens by characterizing the nature of the adaptive immune response. Chickens from the immunized group demonstrated significant increases in SE-specific plasma IgG, intestinal secretory IgA, and lymphocyte proliferative response. The populations of CD4, CD8, and TCR γδ T-cells in immunized chickens were significantly greater than in the controls. Increased levels of IFN-γ, IL-2, IL-6 and IL-10 were observed in peripheral blood mononuclear cells stimulated with SE specific antigen. After virulent SE challenge, the immune system of immunized chickens was rapidly stimulated, as indicated by significantly increased population of CD4 and CD8 T-cells. Furthermore, the immunized group exhibited decreased challenge strain recovery of the internal organs compared to the non-immunized group. Together, these data indicate that the immunization induced humoral and cell-mediated immunity might be responsible for significant reduction of the virulent challenge strain load in the internal organs of immunized chickens.  相似文献   

2.
An attempt was made to develop a vaccine against salmonellosis in poultry by formalizing the Salmonella toxins (enterotoxin plus cytotoxins) that have been found to be the main virulent products of the organisms. Formalized (FT) and carbonated (CT) toxoids were prepared from partially purified toxins of Salmonella enterica subspecies enterica ser. Weltevreden (BM-1643) and S. enterica ser. Gallinarum (L-19/a). There was no mortality in birds vaccinated with formalized toxoid of serovar Weltevreden plus Freund's complete adjuvant (FCA) following homologous or heterologous (S. enterica ser. Gallinarum and S. enterica ser. Typhimurium) challenges. Protection ranged from 50% to 83.3% in the groups immunized with other preparations of S. enterica ser. Weltevreden, i.e. with FT without FCA or with CT with or without FCA. Formalized toxoid prepared from S. enterica ser. Gallinarum (FTSG) toxins given with FCA afforded 100% protection against homologous challenge, but not against heterologous serovars. In the control group, only 16.7% of the birds survived in a subgroup challenged with S. enterica ser. Gallinarum, and none withstood challenge with S. enterica ser. Weltevreden or S. enterica ser. Typhimurium. No untoward reactions were observed in any of the immunized groups. Thus, the vaccine was considered to be potent and safe.  相似文献   

3.
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   

4.
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   

5.
To construct a novel live vaccine candidate for fowl typhoid (FT) caused by Salmonella Gallinarum (SG), the lon and cpxR genes that are related to host-pathogen interaction were deleted from a wild type SG using the allelic exchange method. The mutants were grown normally, as was the wild type. The biochemical properties of the mutants remained very similar to those of the wild-type, while JOL914 (Δlon) and JOL916 (ΔlonΔcpxR) were mucoid. Extracellular polysaccharide increased 30.6-, 1.3-, and 46.2-fold in JOL914, JOL915 (ΔcpxR), and JOL916, respectively. Dot-blot analysis demonstrated significant increases of FimA expression at 6.77-, 2.33-, and 3.90-fold for JOL914, JOL915, and JOL916, respectively. Internalizations of JOL914, JOL915, and JOL916, in chicken abdominal macrophages, were increased at 4.65-, 0.50-, and 2.72-fold, respectively. Virulences of JOL914, JOL915 and JOL916, analyzed by LD50 using 1-week-old chickens, were attenuated approximately at 101-, 101-, and > 103-fold, respectively. The oral inoculations of 2 × 107 cfu of the wild type, JOL914, JOL915 and JOL916 caused 55.6, 16.7, 22.2, and 0.0% mortality, respectively. Significantly moderate gross lesions of the liver and spleen were observed in the JOL916 group compared to the other groups. An induced immune response and significant peripheral mononuclear proliferation reaction were observed in the JOL916 group. At the protection against the wild type challenge, JOL916 offered 100% protection. Thus, the results of this study suggest that JOL916 among the mutants studied represented the safest and most effective live vaccine candidate against FT.  相似文献   

6.
In order to construct a novel vaccine candidate for preventing post-weaning diarrhea in swine, the individual genes for Escherichia coli K88ab, K88ac, FedA, and FedF fimbriae were inserted into a secretion plasmid pBP244 containing asd, lepB, secA, and secB. These were transformed into Salmonella Typhimurium Δlon ΔcpxR Δasd. Secretion of the individual recombinant fimbrial antigens was confirmed by immunoblot analysis. Groups 1 and 2 mice received a single oral dose of the vaccine mixture and S. Typhimurium carrying pBP244 only as a control, respectively. In groups 3 and 4, mice were primed and boosted with the vaccine mixture and S. Typhimurium carrying pBP244 only as a control, respectively. In general, all immunized mice had significantly increased serum immunoglobulin (Ig)G (P < 0.05) and intestinal secretory IgA against the individual fimbrial antigens compared with those mice in the control group. In the IgG2a and IgG1 titer assay, only IgG2a titer was increased in group 1, while both IgG2a and IgG1 titers were increased in group 3. Furthermore, the vaccine strains were not detected in the excreted feces of any immunized mice. Thus, the vaccine candidate can be highly immunogenic and be safe to the environment.  相似文献   

7.
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.  相似文献   

8.
Background: Salmonella Typhimurium, a non-host-adapted Gram-negative intracellular pathogen, is capable of infecting a variety of animal hosts and humans.

Objective: This study utilized the prime-booster immunization strategy using Salmonella Typhimurium–LTB (S. Typhimurium–LTB) ghost with the aim of inducing a robust immune response for the prevention of avian salmonellosis. In addition, the effect of MontanideTM ISA 70VG adjuvant on S. Typhimurium–LTB ghost vaccination was investigated.

Animals and methods: A total of 75 chickens were divided into three groups (n=25) for intramuscular immunization: group A (non-immunized control injected with sterile PBS), group B (immunized with S. Typhimurium–LTB ghost), and group C (immunized with S. Typhimurium–LTB ghost plus MontanideTM ISA70VG adjuvant).

Results: Compared with group A, the immunized chickens (groups B and C) exhibited increased titers of antigen specific plasma IgG and intestinal secretory IgA antibodies. In addition, group C showed enhanced induction of the humoral immune response compared to group B. The populations of splenic CD3+CD4+ and CD3+CD8+ T-cells increased significantly in both immunized groups. In addition, increased mRNA expression of the Th1 cytokines, IFN-γ, and IL-2 were observed in S. Typhimurium antigen-stimulated peripheral blood mononuclear cells from groups B and C chickens. Chickens from both vaccinated groups showed significant protection against virulent S. Typhimurium oral challenge compared to non-vaccinated chickens and a lower challenge strain count was recovered from the internal organs of group C.

Conclusions: Injection of S. Typhimurium-LTB ghost with or without MontanideTM ISA70VG adjuvant is capable of inducing protective immunity against the virulent S. Typhimurium infection in chickens.  相似文献   


9.
Efficacy of a new live Salmonella Typhimurium vaccine candidate attenuated by two virulence gene deletions was evaluated in this study. Live form of the vaccine was orally administered and formalin-inactivated form was intramuscularly (IM) administered. 105 female BALB/c mice were used and divided into 5 groups, A to E, containing 21 mice per group. Serum IgG and secretory IgA titers and levels of serum IFN-γ, IL-4, TNF-α, IL-12 of the immunized groups, especially group C (oral prime-oral booster) significantly increased. In addition, all animals in groups C showed no clinical symptoms and survived the virulent challenges, whereas all or some of mice from the other groups died of the challenge. These indicate that the vaccine candidate can be an effective tool for prevention of Salmonella infections by inducing robustly protective immune responses and leading to the production of inflammatory cytokines. Booster immunization, especially via oral administration, is necessary to optimize its protection.  相似文献   

10.
Yu X  Jia R  Huang J  Shu B  Zhu D  Liu Q  Gao X  Lin M  Yin Z  Wang M  Chen S  Wang Y  Chen X  Cheng A 《Veterinary research》2012,43(1):56
Orally delivered DNA vaccines against duck enteritis virus (DEV) were developed using live attenuated Salmonella typhimurium (SL7207) as a carrier and Escherichia coli heat labile enterotoxin B subunit (LTB) as a mucosal adjuvant. DNA vaccine plasmids pVAX-UL24 and pVAX-LTB-UL24 were constructed and transformed into attenuated Salmonella typhimurium SL7207 resulting SL7207 (pVAX-UL24) and SL7207 (pVAX-LTB-UL24) respectively. After ducklings were orally inoculated with SL7207 (pVAX-UL24) or SL7207 (pVAX-LTB-UL24), the anti-DEV mucosal and systemic immune responses were recorded. To identify the optimum dose that confers maximum protection, we used different doses of the candidate vaccine SL7207 (pVAX-LTB-UL24) during oral immunization. The strongest mucosal and systemic immune responses developed in the SL7207 (pVAX-LTB-UL24) (1011 CFU) immunized group. Accordingly, oral immunization of ducklings with SL7207 (pVAX-LTB-UL24) showed superior efficacy of protection (60-80%) against a lethal DEV challenge (1000 LD50), compared with the limited survival rate (40%) of ducklings immunized with SL7207 (pVAX-UL24). Our study suggests that the SL7207 (pVAX-LTB-UL24) can be a candidate DEV vaccine.  相似文献   

11.
To evaluate the efficacy of a novel attenuated Salmonella Enteritidis (△lon△cpxR) vaccine candidate (JOL919), chickens were immunized through oral and intramuscular routes to reduce egg contamination against S. Enteritidis challenge. Birds were orally immunized with JOL919 on the first day of life and were subsequently boosted in the 6th and 16th weeks through oral (group B) or intramuscular (group C) route, while control birds were unimmunized (group A). The chickens of all groups were challenged intravenously with the virulent S. Enteritidis strain in the 24th week. The immunized groups B and C showed significantly higher plasma IgG and intestinal secretory IgA levels as compared to those of the control group. The lymphocyte proliferation response and CD45+CD3+ T‐cell number in the peripheral blood of the groups B and C were significantly increased. In addition, the egg contamination rates were significantly lower in the group B (0%, 10.7% and 0%) and the group C (3.6%, 14.3% and 3.6%) as compared to the group A (28.6%, 42.8% and 28.6%) in the 1st, 2nd and 3rd weeks post‐challenge. All animals in the groups B and C showed lower organ lesion scores in the liver and spleen and lower bacterial counts in the liver, spleen and ovary at the 3rd week post‐challenge. These results indicate that this vaccine candidate can be an efficient tool for prevention of Salmonella infections by inducing protective humoral and cellular immune responses. In addition, this vaccine did not prevent egg contamination, but did appear to reduce incidence. Booster immunizations, especially via oral administration route, showed an efficient protection against internal egg contamination with S. Enteritidis.  相似文献   

12.
The parasite Neospora caninum is an important abortifacient agent in cattle worldwide. At present, the development of an effective and safe vaccine against bovine neosporosis is of great relevance. Recently, a new isolate of N. caninum (Nc-Spain 1 H) which was obtained from the brain of an asymptomatic congenitally infected calf, exhibited non-virulent behaviour in mouse and bovine infection models. The aim of this study was to determine the safety and efficacy of Nc-Spain 1 H when used as a vaccinal isolate in well-established BALB/c models of congenital and cerebral neosporosis. Mice were subcutaneously immunised twice at 3-week intervals and were challenged with 2 × 106 tachyzoites of the virulent Nc-Liv isolate. After immunisation with live Nc-Spain 1 H tachyzoites, no parasitic DNA was detected in the dams’ brains before challenge and microsatellite analysis performed in PCR-positive mice showed that the profiles corresponded to the challenge isolate Nc-Liv, indicating the Nc-Spain 1 H isolate to be a safe vaccine candidate. The efficacy of the live vaccine was evaluated in the first experiment after the immunisation of mice with 5 × 105 live Nc-Spain 1 H tachyzoites. This immunisation protocol significantly reduced the neonatal mortality to 2.4%, reduced the vertical transmission from 89.1% to 2.3% and completely limited the cerebral infection. These results were associated with a Th1-type immune response. In the second experiment, the effect of various immunising doses was established using ten-fold dilutions of the tachyzoites (from 5 × 105 to 5 × 10). In all the cases, congenital protection rates above 60% were observed, and the mice that were immunised with the lowest dose (5 × 10) presented the highest protection rate (86%). Moreover, low immunising doses of Nc-Spain 1 H induced an IgG2a response, and high parasitic doses induced an IgG1 response. These results evidence the safety and the efficient protection that was conferred by Nc-Spain 1 H against congenital neosporosis, even when the mice were immunised with low parasitic doses.  相似文献   

13.
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   

14.
The protective efficacy of DNA plasmids encoding avian infectious bronchitis virus (IBV) S1, N, or M protein was investigated in chickens. Chickens were inoculated monovalently (with plasmid pVAX1-16S1, pVAX1-16M, or pVAX1-16N alone) or multivalently (combination of the three different plasmids, pVAX1-16S1/M/N). A prime-boost immunization protocol against IBV was developed. Chickens were immunized with the multivalent DNA vaccine twice and then boosted with an inactivated vaccine once. Antibody titers of the chickens immunized with pVAX1-16S1/M/N were much higher than those of the monovalent groups (p < 0.01). A protective rate up to 90% was observed in the pVAX1-16S1/M/N group. The serum antibody titers in the prime-boost birds were significantly higher than those of the multivalent DNA vaccine group (p < 0.01) but not significantly different compared to the inactivated vaccine group at 49 days of age. Additionally, the prime-boost group also showed the highest level of IBV-specific cellular proliferation compared to the monovalent groups (p < 0.01) but no significant difference was found compared to the multivalent DNA vaccine group, and the prime-boost group completely protected from followed viral challenge.  相似文献   

15.
This study compared a new live attenuated Salmonella Enteritidis vaccine candidate secreting Escherichia coli heat-labile enterotoxin B subunit (SE-LTB) with a commercial Salmonella Enteritidis (SE) vaccine for efficacy of protection against SE infection in laying hens. Chickens were divided into 3 groups of 20 each. Group A chickens were inoculated orally with phosphate-buffered saline and served as controls, group B chickens were inoculated orally with the vaccine candidate, and group C chickens were inoculated intramuscularly with a commercial vaccine, the primary inoculation in groups B and C being at 10 wk of age and the booster at 16 wk. Groups B and C showed significantly higher titers of plasma immunoglobulin G, intestinal secretory immunoglobulin A, and egg yolk immunoglobulin Y antibodies compared with the control group, and both vaccinated groups showed a significantly elevated cellular immune response. After virulent challenge, group B had significantly lower production of thin-shelled and/or malformed eggs and a significantly lower rate of SE contamination of eggs compared with the control group. Furthermore, the challenge strain was detected significantly less in all of the examined organs of group B compared with the control group. Group C had lower gross lesion scores only in the spleen and had lower bacterial counts only in the spleen, ceca, and ovary. These findings indicate that vaccination with the SE-LTB vaccine candidate can efficiently reduce internal egg and internal organ contamination by Salmonella and has advantages over the commercial vaccine.  相似文献   

16.
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   

17.
Escherichia coli heat-labile enterotoxin B subunit (LTB) protein is a potent mucosal adjuvant. In this study, the effect of an attenuated Salmonella secreting LTB protein as an adjuvant strain (JOL1228) for a live Salmonella Enteritidis (SE) vaccine candidate (JOL919) was evaluated. In a single immunization experiment, chickens immunized with a mixture of JOL919 (5 parts) and JOL1228 (1 part) showed enhanced mucosal and cellular immune responses and efficient protection against salmonellosis as compared to those unimmunized control chickens. In further analysis, chickens were primed at one day of age and were boosted at the fifth week of age to prolong immune responses and to maximize the protection efficacy against salmonellosis. The immunized groups B (prime and booster with JOL919), C (prime with JOL919-JOL1228 mixture and booster with JOL919), and D (prime and booster with JOL919-JOL1228 mixture) showed significantly higher humoral and cellular immune responses as compared to those in the unimmunized control group A. In addition, immunized groups C and D showed fewer gross lesions in the liver and spleen and a lower number of SE-positive organs, with the lowest bacterial counts in the SE challenge strain as compared to the control group. These results indicate that SE vaccination with the LTB strain can have an adjuvant effect on the vaccine candidate by enhancing immune responses, and that a prime-boost strategy with the addition of the adjuvant strain can efficiently protect birds against salmonellosis.  相似文献   

18.
We have previously developed a novel attenuated Salmonella Typhimurium (S. Typhimurium) ΔcpxR Δlon vaccine. This study was carried out to examine whether this vaccine could effectively protect growing piglets against Salmonella infection. Attenuated S. Typhimurium secreting the B subunit of Escherichia coli heat-labile enterotoxin was also used as a mucosal adjuvant. Pregnant sows in groups A and B were primed and boosted with the vaccine and mucosal adjuvant, whereas sows in groups C, D and E received PBS. Piglets in groups A and C were intramuscularly primed with formalin-inactivated vaccine and orally boosted with live vaccine, while piglets in groups B, D and E received PBS. Piglets in groups A, B, C, and D were challenged with a wild type virulent S. Typhimurium at the 11th weeks of age. Colostrum sIgA and IgG titers in vaccinated groups A and B sows were approximately 50 and 40 times higher than those of non-vaccinated groups C, D and E sows (P < 0.001). Serum IgG titers of group A piglets were also significantly higher than those of groups D and E piglets during the study (P < 0.001). Furthermore, no clinical signs were observed in group A piglets during the entire experimental period after the challenge, while diarrhea was observed in many of the piglets in groups B, C, and D. No Salmonella was isolated from fecal samples of the groups A and C piglets on day 14 after challenge, whereas the challenge strain was isolated from several piglets in groups B and D. These results indicate that vaccination of the piglets with the vaccine and mucosal adjuvant in addition to vaccination of their sows induced effective protection against Salmonella infections in the growing piglets.  相似文献   

19.

Background

Microbiological standards within pork slaughter processing plants in the European Union are currently governed by Commission Regulation (EC) 2073/2005, which describes detailed performance criteria at specific stages of the procedure (following carcass dressing and before chilling) for total viable counts (TVC), Enterobacteriaceae (EB) and Salmonella spp. In this study, 95 carcasses from an Irish pork slaughter plant were sampled by swabbing 100 cm2 of surface at three sites (belly, ham, jowl) to examine the effects of eight processing stages (stunning, bleeding, scalding, singeing, polishing, evisceration, final inspection and chilling) on contamination levels.

Results

TVC ranged from approximately 1.7–6.3 log cfu cm2 during sampling. There were significant reductions in TVC for all sites after scalding and singeing (p < 0.05), whilst there was a significant increase in counts after polishing and evisceration (p < 0.05) compared with preceding stages. EB counts indicated hygienic weak points in the examined slaughter plant leading to faecal (cross)-contamination, with elevated counts after stunning, bleeding and evisceration (p < 0.05), compared with final counts after chilling.

Conclusions

Although the bacterial numbers reported in this study may reflect specific plant practices and temporal influences, results show that contamination can be introduced at various steps in the process and highlight the importance of monitoring locations other than those required by legislation within the process. Monitoring can be used to establish baseline levels for high-risk stages specific to each plant and to assess the effectiveness of additional interventions.  相似文献   

20.
1. The aim of the present study was to determine if the 9R-strain of the Salmonella Gallinarum live vaccine was responsible for having fowl typhoid outbreaks in chicken flocks from both chicken and turkey breeders as well as to verify the antimicrobial resistance of the isolates from the outbreaks.

2. The triplex polymerase chain reaction, standard antimicrobial test, beta-lactamase genes identification and Ion Torrent PMG whole-genome sequence were used in the field isolates and in the vaccine strain of S. Gallinarum.

3. The 60 tested isolates were not from vaccine origin and manifested high resistance to drugs from macrolide and quinolone groups. Whole-genome sequencing (WGS) and single nucleotide polymorphism analysis on selected isolates for core genes from Salmonella enterica confirmed the wild origin of these isolates and showed two possible sources of S. Gallinarum in the studied outbreaks.

4. S. Gallinarum isolated from fowl typhoid outbreaks in the studied period were not caused by the use of the SG9R live vaccine. The source of strains sequenced was diverse.  相似文献   

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