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1.
SlyA protein plays a key role in virulence in Salmonella enterica. In this study, we evaluated the ability of the slyA mutant strain of S. enterica serovar Choleraesuis ( S. choleraesuis) to protect against swine salmonellosis. Using a murine model infected with S. enterica serovar Typhimurium ( S. typhimurium), we showed that the Salmonella strain with a deletion of slyA could be used as a highly immunogenic, effective and safe vaccine in mice. Based on these data, a slyA mutant of S. enterica serovar Choleraesuis strain RF-1 was constructed, and the ability of this mutant to protect immunized pigs from S. choleraesuis infection was examined. As with the S. typhimurium slyA mutant, immunization of pigs with the S. choleraesuis slyA mutant strain provided significant protection against subsequent challenge by the wild-type RF-1. These results demonstrate that SlyA is a potential target in the development of a novel live attenuated vaccine against S. enterica. 相似文献
2.
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
3.
用不同剂量的口蹄疫灭活疫苗免疫3组雌性BALB/c小鼠,同时设空白对照组,每组8只。免疫后每7d采血一次,用液相阻断ELISA(LPB-ELISA)检测血清抗体水平;第28d用800LD50同源强毒攻击,攻毒后36h,每组随机选取3只BALB/c小鼠,采全血,分别用每只BALg/c小鼠全血注射12只乳鼠,每组共注射36只乳鼠,以乳鼠试验判定BALB/c小鼠的病毒血症和攻毒保护情况。结果表明,免疫组BALB/c小鼠均可产生特异性抗体,保护率分别为75.0%、63.9%、36.1%;对照组小鼠血清抗体为阴性。提示,BALB/c小鼠可以用来评价口蹄疫灭活疫苗的免疫效力。 相似文献
4.
Calves were vaccinated orally, subcutaneously or intraperitoneally with a smooth, plasmid-cured strain of Salmonella enterica serovar typhimurium, strain 81. Oral vaccination was not effective, as only 1/5 calves survived challenge with virulent S. typhimurium. Strain 81 was attenuated for calves, as only a slight rise in rectal temperatures was detected after vaccination. The organism was excreted by some calves in the faeces, but no signs of diarrhoea were observed after vaccination. After parenteral vaccination, strain 81 was able to reach the intestines, gastric associated lymphoid tissues and other internal lymphoid tissues and remained viable for up to 14 days in the bovine host. After oral challenge with a virulent strain, 9/10 vaccinated calves survived challenge as opposed to 4/10 control calves ( p<0.5). Diarrhoea was present in all calves of the control groups, but in only 4/10 of the vaccinated calves. The clinical reactions of the vaccinated calves were milder than in the control calves, as the rises in rectal temperatures were lower, diarrhoea was less severe, and the challenge strain was present in fewer organs from vaccinated calves than control calves. This study showed that parenterally administered Salmonella vaccines can induce both mucosal and systemic immunity, and it is postulated that this capability of strain 81 is related to its colonisation of lymphoid tissues and other systemic and intestinal tissues. This study confirmed that plasmid-cured strains were attenuated in the bovine host and conferred significant protection after parenteral vaccination, but not oral vaccination. 相似文献
5.
为评估鸡白痢沙门菌减毒候选疫苗株对环境应激及消毒剂的抵抗力,本研究对S6702△rfaG△csgA、S6702△rfaL△csgA、S6702△rfaG△csgA△ompR和S6702△rfaL△csgA△ompR等4种鸡白痢沙门菌双基因缺失株和三基因缺失株进行了生长曲线、生物被膜形成能力、药敏试验、环境应激试验及消毒剂的灭活效果的测定。结果显示,4株缺失株均丧失生物被膜形成能力并保留了与亲本株相似的药物敏感性。多基因缺失株对pH为4.0和8.0的培养条件较野生菌株和单基因缺失株更为敏感,呈现微耐酸和不耐碱的特性;所有菌株对54℃热处理和紫外线处理均敏感。消毒剂对实验菌株的杀灭效果显示,野生菌株和各基因缺失株均对0.01%的聚维酮碘溶液敏感,基因缺失株相比野生菌株过硫酸氢钾复合物更为敏感。因此,鸡白痢沙门菌减毒候选疫苗株对环境应激的抵抗力均有所降低,本研究为该菌后续候选疫苗株的进一步筛选奠定了基础。 相似文献
6.
BackgroundAttenuated Salmonella strain can be used as a vector to transport immunogens to the host antigen-binding sites. ObjectivesThe study aimed to determine the protective efficacy of attenuated Salmonella strain expressing highly conserved Brucella immunogens in goats. MethodsGoats were vaccinated with Salmonella vector expressing individually lipoprotein outer-membrane protein 19 (Omp19), Brucella lumazine synthase (BLS), proline racemase subunit A (PrpA), Cu/Zn superoxide dismutase (SOD) at 5 × 10 9 CFU/mL and challenge of all groups was done at 6 weeks after vaccination. ResultsAmong these vaccines inoculated at 5 × 10 9 CFU/mL in 1 mL, Omp19 or SOD showed significantly higher serum immunoglobulin G titers at (2, 4, and 6) weeks post-vaccination, compared to the vector control. Interferon-γ production in response to individual antigens was significantly higher in SOD, Omp19, PrpA, and BLS individual groups, compared to that in the vector control (all p < 0.05). Brucella colonization rate at 8 weeks post-challenge showed that most vaccine-treated groups exhibited significantly increased protection by demonstrating reduced numbers of Brucella in tissues collected from vaccinated groups. Real-time polymerase chain reaction revealed that Brucella antigen expression levels were reduced in the spleen, kidney, and parotid lymph node of vaccinated goats, compared to the non-vaccinated goats. Besides, treatment with vaccine expressing individual antigens ameliorated brucellosis-related histopathological lesions. ConclusionsThese results delineated that BLS, Omp19, PrpA, and SOD proteins achieved a definite level of protection, indicating that Salmonella Typhimurium successfully delivered Brucella antigens, and that individual vaccines could differentially elicit an antigen-specific immune response. 相似文献
7.
A questionnaire-based, retrospective field study was conducted in 78 Danish broiler houses (analytical units) on 42 farms. In spring 1997, all these broiler houses had been infected with Salmonella Enteritidis, phage type 8, and/or Salmonella Typhimurium, definitive-type 66, by day-old chicks delivered from the same hatchery. Because these two salmonella types had not been detected in the Danish broiler sector before and the broiler houses were infected in a period of low salmonella prevalence, the study could focus on farm-related factors, without being distorted by other salmonella infections. The same person visited all 78 broiler houses, and farm-related factors were listed both from personal observations and by interrogating the person in charge of attending to the broilers. Additional factors (noted at the visits) were recorded in a later telephone interview. Altogether, 187 variables were analyzed. Broiler houses were divided into single-infection houses (which had one or both of the salmonella types in only one crop), and multiple-infection houses (where infection occurred in multiple crops). This was done both generally and separately for each of the salmonella types. Factors associated with house status—but that were beyond the control of the farmer—were the salmonella type and the percentage of salmonella positive samples in the first crop. Factors which could be controlled by the farmer and which were associated with reduced prevalence of multiple-infection houses included antiseptic soap and water for washing hands in the anteroom, hygiene barriers when removing dead broilers, gravel alongside the broiler house, systematic checks of indoor rodent-bait depots, and combined surface and pulse-fogging disinfection. 相似文献
8.
In this study we examined the extent of biofilm formation in field strains of Salmonella enterica serovar Typhimurium ( S. Typhimurium), an important foodborne pathogen. Ninety-four field strains of S. Typhimurium were tested for their ability to form biofilm and components contributing to its formation. Most S. Typhimurium strains were highly capable of biofilm formation except for strains of phage type DT2 originating from pigeons. The most efficient biofilm forming strains were those of phage type DT104 positive for Salmonella genomic island 1 (SGI1). A comparison of SGI1 positive and negative strains indicated that the increased biofilm formation of SGI1 positive strains was associated with the presence of this genomic island. Finally, in five strains we found an alternative strategy of biofilm formation independent of curli fimbriae and cellulose production but solely dependent on an overproduction of capsular polysaccharide. Due to a mucoid and brown appearance on Congo Red agar we designated these strains as belonging to the SBAM (smooth brown and mucoid) morphotype. 相似文献
9.
The efficacy of a live attenuated Salmonella Typhimurium Megan Vac 1 vaccine (MV1) was evaluated against Salmonella Enteritidis in chicken pullets with the use of PCR and culture methods. Two hundred Hyline W-32 white leghorn chicks were obtained from a local hatchery and divided into four treatment groups. Two of the groups served as positive and negative controls. The MV1 vaccine was administered to the chicks in the remaining two groups at 1 and 35 days old by either the coarse spray (field) or the oral route (laboratory) method. The chicks were challenged with a high dose of a Salmonella Enteritidis strain at 10 wk old and euthanatized 3 days postinoculation. Samples for PCR analysis were collected prior to enrichment, after pre-enrichment in buffered peptone water (BPW) and after primary enrichment from the ceca, liver, and spleen. None of the samples tested yielded positive results for the Salmonella Typhimurium vaccine strain by either the culture or PCR methods. Results from the standard culture method showed that vaccinating the birds with MV1 reduced the counts of Salmonella Enteritidis recovered from the challenged birds. In addition, fewer pre-enriched samples tested positive for Salmonella Enteritidis among the challenged groups that were vaccinated when compared to the unvaccinated challenged group. Under the conditions of this study, MV1 was unable to prevent colonization of other internal organs such as the liver and spleen. Real-time PCR was significantly more sensitive than conventional PCR (C-PCR) prior to enrichment, but after enrichment the sensitivities of the two methods were similar. Enrichment significantly increased the sensitivity of both PCR methods for the detection of Salmonella Enteritidis in cecal samples, but did not significantly increase the sensitivity for detection of Salmonella Enteritidis in liver and spleen samples that were pre-enriched in BPW. There was no significant difference between the laboratory or field vaccination methods with respect to either the prevalence of Salmonella Enteritidis isolation or the bacterial loads in culture-positive samples. Collectively, the data suggest that MV1 offered some protection against Salmonella Enteritidis in commercial layer chick pullets under the conditions of this study. Given the labor and time required to perform the C-PCR and culture methods, the real-time PCR method may prove to be a more useful method to use in diagnostics. 相似文献
10.
This study aimed to investigate the relatedness of porcine Salmonella enterica subsp. enterica (S.) serovar Typhimurium strains isolated in Southern Brazil. Sixty-six isolates from pigs belonging to three commercial companies were submitted to phage typing, XbaI-macrorestriction (PFGE), IS200 hybridization, rep-PCR, antimicrobial susceptibility testing, and PCR assay targeting the spvR region. All strains presented a unique rep-PCR pattern and 63 strains had a common IS200 profile. One pulse-type (XA) was the most prevalent (39/66 strains) and included strains of phage types DT177, DT192, DT194 and RDNC. The spvR region was detected in three strains, which harboured plasmids of 90 kb. High rates of tetracycline, sulfonamide and streptomycin resistance were found. Isolates from farms located in different geographic regions but associated to the same commercial companies clustered together and presented a common resistance profile. Results suggested that clonal groups of S. Typhimurium are present in pig commercial companies in Southern Brazil. 相似文献
11.
旨在分离鼠伤寒沙门菌烈性噬菌体,为控制该病原菌感染或污染提供生物制剂.以1株从市售散装牛奶中分离到的多重耐药性鼠伤寒沙门菌为宿主菌,采用人工诱导方法,连续1周每日给3只试验鸡饲喂宿主菌悬液,7 d后,采用双层琼脂平板法从试验鸡粪便中分离培养噬菌体,并对其效价、核酸类型、宿主谱、热稳定性与酸碱耐受性以及对鼠伤寒沙门菌感染... 相似文献
12.
Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella typhimurium) can infect and cause disease in a wide range of host species however there have been suggestions that this serovar may have genes involved with host range or specificity [Tsolis, R.M., Townsend, S.M., Miao, E.A., Miller, S.I., Ficht, T.A., Adams, L.G., Baumler, A.J., 1999. Identification of a putative S. enterica serotype Typhimurium host range factor with homology to IpaH and YopM by signature-tagged mutagenesis. Infect. Immun. 67 (12), 6385-6393]. Our goal in this study was to determine if in vitro virulence assays would support this suggestion. Twelve human and 10 bovine isolates of S. typhimurium from a single county in California were evaluated using in vitro virulence assays of adhesion and invasion. The resulting data was combined with results from previously reported genotypic and phenotypic testing of the isolates and statistical analysis performed using multivariate general linear models. Human isolates had higher adhesion values in each of the statistical models tested (p<0.05) but no statistical differences were found in the invasion values of human and bovine source isolates. Both adhesion and invasion values differed between the two largest groups of isolates segregated on the basis of pulsed-field gel patterns. The findings suggest there may be genetically defined in vitro virulence attributes in S. typhimurium that are associated with host species. 相似文献
13.
Salmonella enterica remains one of the most important food-borne pathogens of humans and is often acquired through consumption of infected poultry meat or eggs. Control of Salmonella infections in chicken is therefore an important public health issue. Infection with S. enterica serovar Typhimurium results in a persistent enteric infection without clinical disease in chickens of more than 3 days of age, and represents a source for contamination of carcass at slaughter and entry into the human food chain. Data presented indicate a profound effect of age at initial exposure on the persistence of infection and a lesser effect on the development of effective immunity to re-challenge. The percentage of birds positive for Salmonella was high until 8–9 weeks of age, regardless of the age at which the birds were infected (1, 3 or 6 weeks). The birds infected at 3 and 6 weeks of age produced a more rapid and higher antibody response (IgY and IgA) than those infected at 1 week of age, but in all cases infection persisted for a considerable period despite the presence of high antibody levels. Following a re-challenge infection with S. Typhimurium, all three previously-infected groups had fewer bacteria in the gut, spleen and liver compared with age-matched birds receiving a parallel primary infection. However, the birds primary infected at 3 and 6 weeks of age cleared infection more rapidly than those infected at a younger age. Interestingly older-primed birds had higher specific T lymphocyte proliferative responses and specific circulating levels of IgY antibody at time of re-challenge. Although birds initially infected at 1 week of age and those that were previously uninfected produced a stronger antibody response following re-challenge, they were slower to clear Salmonella from the gut than the older-primed groups which expressed a stronger T lymphocyte response. The data presented indicate that clearance of Salmonella from the gut is age-dependent and we propose that this relates to the increased competence of the enteric T cell response. The findings that Salmonella persists beyond 8–9 weeks, irrespective of age at exposure, has implications for the broiler sector and indicates the need to remain Salmonella free throughout the rearing period. Moreover, the re-challenge data demonstrates that infection at a young age is less effective in producing protective immunity than in older chickens. This feature of the development of protective immunity needs to be considered when developing vaccines for the broiler sector of the poultry industry. 相似文献
14.
Salmonella (S.) Typhimurium and S. Enteritidis are the major causative agents of food-borne illnesses worldwide. Currently, a rapid detection system using multiplex real-time polymerase chain reaction (PCR) has been applied for other food-borne pathogens such as Escherichia coli, Staphylococcus aureus and Streptococcus spp. A multiplex real-time PCR was developed for the simultaneous detection of Salmonella spp., especially S. Typhimurium and S. Enteritidis, in beef and pork. For the specific and sensitive multiplex real-time PCR, three representative primers and probes were designed based on sequence data from Genbank. Among the three DNA extraction methods (boiling, alkaline lysis, and QIAamp DNA Mini Kit), the QIAamp DNA Mini Kit was the most sensitive in this study. The optimized multiplex real-time PCR was applied to artificially inoculated beef or pork. The detection sensitivity of the multiplex real-time PCR was increased. The specificity of the multiplex real-time PCR assay, using 128 pure-cultured bacteria including 110 Salmonella isolates and 18 non-Salmonella isolates, was 100%, 100% and 99.1% for Salmonella spp., S. Typhimurium and S. Enteritidis, respectively. The sensitivity was 100%, 100% and 91.7% for Salmonella spp., S. Typhimurium and S. Enteritidis, respectively. The multiplex real-time PCR assay developed in this study could detect up to 0.54 ± 0.09 and 0.65 ± 0.07 log 10 CFU/ml for S. Typhimurium and S. Enteritidis for beef, 1.45 ± 0.21 and 1.65 ± 0.07 log 10 CFU/ml for S. Typhimurium and S. Enteritidis for pork, respectively, with all conditions optimized. Our results indicated that the multiplex real-time PCR assay developed in this study could sensitively detect Salmonella spp. and specifically differentiate S. Typhimurium from S. Enteritidis in meats. 相似文献
15.
Background: Salmonella enter/ca serovar Typhimurium is a major foodborne pathogen worldwide. S. Typhimurium encodes type III secretion systems via Salmonella pathogenicity islands (SPI), producing the major effector proteins of virulence. Previously, we identified two genes of Salmonella pyruvate metabolism that were up-regulated during chicken cell infection: pyruvate formate lyase I (pf/B) and b/functional acetaldehyde-CoA/alcohol dehydrogenase (adhE). We were therefore interested in examining the role these genes may play in the transmission of Salmonella to humans. Methods: Mutant strains of Salmonella with single gene deletions for pflB and adhE were created. Invasion and growth in human HCT-8 intestinal epithelial cells and THP-1 macrophages was examined. Quantitative PCR was performed on 19 SPI-1 genes. Results: In HCT-8 cells, both mutant strains had significantly higher intracellular counts than the wild-type from 4 to 48 h post-infection. Various SPI-1 genes in the mutants were up-regulated over the wild-type as early as 1 h and lasting until 24 h post-infection. In THP-1 cells, no significant difference in internal Salmonella counts was observed; however, SPI-1 genes were largely down-regulated in the mutants during the time-course of infection. We also found five SPI-1 genes - hilA, hiIC hill), sicP and rtsA - which were up-regulated in at least one of the mutant strains in log-phase broth cultures alone. We have therefore identified a set of SPI-1 virulence genes whose regulation is effected by the central metabolism of Salmonella. 相似文献
16.
AIM: To examine the infective dose, incubation period and disease progression of an isolate of Salmonella enterica serotype Typhimurium definitive type 160 (DT160) originating from a naturally-infected house sparrow ( Passer domesticus) during an outbreak of the disease in New Zealand. METHODS: Thirty-six house sparrows captured from the wild and free of Salmonella spp were divided into six groups of six birds, housed individually, and inoculated orally with phosphate buffered saline (PBS) or 10 1, 10 2, 10 3, 10 5, 2 × 10 8 colony forming units (cfu) of the outbreak strain of S. Typhimurium DT160. The birds were observed for 10 days for clinical signs and/or mortality, and faecal samples were collected to determine excretion of S. Typhimurium. The birds were eutha- nised 11 days post-inoculation (p.i.) and a wide range of tissue samples were collected for histopathological examination, and culture and typing of Salmonella spp. Macro-restriction profiling by pulsed-field gel electrophoresis (PFGE) using XbaI was performed for the epidemiological typing of S. Typhimurium DT160 isolates. RESULTS: Mortality in house sparrows inoculated with S. Typhimurium DT160 was dose-dependent, and 2/6 birds inoculated with 105 cfu and all six birds inoculated with 2 × 10 8 cfu died during the study. Infected sparrows displayed few clinical signs, apart from diarrhoea and/or polyuria, fluffed plumage, and sitting on the floor of the cage. Faecal excretion of DT160 occurred briefly in two birds inoculated with 10 2 cfu and four birds inoculated with 10 3 cfu, on most days in five birds inoculated with 10 5 cfu, and continuously in six birds inoculated with 2 × 10 8 cfu. DT160 was isolated from the livers of three birds which received 10 3 cfu, five birds dosed with 10 5 cfu, and all six birds given 2 × 10 8 cfu. Following necropsy, histopathological lesions similar to those seen in the natural disease were observed in the liver or spleen of three birds which received 10 3 cfu, and all birds dosed with ≥10 5 cfu. CONCLUSION: The results indicate that an isolate of S. Typhimurium DT60 originating from house sparrows in New Zealand is pathogenic to these birds and that the response is dose- dependent. The persistence and excretion of the pathogen may last for at least 10 days. This confirms that sparrows infected with DT160 could be a source of infection to humans and other in-contact animals. 相似文献
17.
将150只BALB/c小鼠随机分成5组。用猪链球菌2型pET32a-Sly、pET32a-38ku和pET32a-Sly-38ku表达的重组蛋白制备的疫苗,以及猪链球菌2型全菌灭活疫苗分别免疫A、B、C、D组小鼠,E组为生理盐水对照。首免后第2周加强免疫1次,二免后第2周,用致死量强毒猪链球菌2型四川分离株和江苏分离株以及马链球菌兽疫亚种安徽分离株攻毒,观察攻毒后对小鼠的免疫保护率。结果,A组与C、D组对猪链球菌2型感染的保护率差异显著(P〈0.05),而C组与D组之间保护率无显著差异;A、B、C、D组之间对马链球菌兽疫亚种安徽分离株感染的保护率差异不显著;各免疫组的保护率极显著高于对照组。结果表明,3种重组疫苗具有良好的免疫原性,能对强毒株猪链球菌2型的攻击感染起到保护作用。 相似文献
18.
To determine if there were significant differences produced by 5 of the most prevalent causes of equine enterocolitis, we studied retrospectively the gross and microscopic pathology of 90 cases of enterocolitis submitted to the San Bernardino laboratory of the California Animal Health and Food Safety Laboratory. Included were cases caused by Clostridium perfringens type C (CP; n = 20), Clostridioides difficile (CD; n = 20), Paeniclostridium sordellii (PS; n = 15), Salmonella enterica subspecies enterica serovar Typhimurium (ST; n = 20), and NSAID intoxication (NS; n = 15). Grossly, necrotizing hemorrhagic typhlocolitis was seen most frequently in cases of CD, ST, and NS disease. Cases of CP and PS had enteritis or colitis in similar percentages. Congestion, hemorrhage, and pleocellular inflammatory infiltrates followed by mucosal and submucosal necrosis were the main lesions found in horses with enteritis or colitis produced by any of the etiologic agents investigated. Severe lesions were more frequent in cases of CD and CP than in cases associated with any of the other 3 etiologies. Pseudomembranes were observed with similar prevalence in the small intestine and colon affected by all agents studied. Thrombosis of the lamina propria and/or submucosa was observed in ~50% of the cases of enteritis and colitis by all etiologies, except for PS, in which the majority of the cases had thrombosis. Gross and microscopic lesions of enterocolitis were not sufficiently specific for any of these etiologic agents to enable these enteritides to be distinguished by gross and/or histologic examination. 相似文献
19.
本试验将减毒鸡沙门氏菌97A疫苗株分别以不同剂量经口服和肌肉注射接种10日龄AA肉鸡,结果表明,97A对10日龄雏鸡有良好安全性。将97A分别以10 相似文献
20.
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 H 2O 2, loss of NO metabolism, and absence of Salmonella pathogenicity island (SPI)-2 expression, respectively. A triple-deletion mutant, SGΔ3 (SGΔ rpoSΔ hmpΔ ssrAB), 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 × 10 6 or 1 × 10 8 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
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