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1.
Relationship between virulence of Chlamydia psittaci strains and establishment of persistent infection of McCoy cells 总被引：1，自引：0，他引：1
The pathogenicity of chlamydial strains for their natural hosts and their ability to induce persistent infections in McCoy cells were compared. Both virulent and avirulent strains persistently infected McCoy cells, but the appearance of the cell culture varied between strains. Avirulent strains induced completely inapparent persistent infection (infection Type 1), while with invasive strains the culture alternated between periods of cell multiplication and periods of extensive cytopathic change (infection Type 2). The virulence of virulent strains was not attenuated, even after 6 months of culture, but after 2 or 3 months some avirulent strains produced infection Type 2 and became invasive for mice and abortive for ewes. This variation of virulence was accompanied by a modification of protein patterns. 相似文献
2.
Safety,immunogenicity, and efficacy of two Escherichia coli cya crp mutants as vaccines for broilers
Attenuated derivatives (delta cya delta crp mutants) of an O2 and an O78 avian septicemic Escherichia coli strain were used to immunize broiler chickens by spray to determine the safety, immunogenicity, and efficacy of the derivatives in single- and double-dose regimens. In the safety and immunogenicity studies, groups of 10 chickens were vaccinated by spray (droplet size approximately 20 microm) with the parent E. coli, the mutant organisms, or phosphate-buffered saline (PBS) at 14 days of age and euthanatised 21 days later. There was no deaths or gross pathologic finding in any of the chickens immunized with the vaccine strains. Compared with the levels in chickens exposed to PBS, there were significantly higher levels of immunoglobulin (Ig) G antibody in serum and air sac washings and of IgA antibody in air sac washings in response to the virulent parent strains than to the vaccine strains. In efficacy studies, chickens were immunized with the O2 or the O78 vaccine strain or PBS at day 14 and with the O2 vaccine strain or PBS at days 10 and 14 and challenged with the parent strain 10 days after the last vaccination. There was no significant difference in local IgA and IgG and serum IgG responses between vaccinated and control groups. Chickens vaccinated with the O2 strain, but not the O78 strain, had significantly lower air sac lesion scores compared with those of the unvaccinated groups in both single- and double-dose regimens. We conclude that the mutant O2 strain provided moderate protection against airsacculitis. 相似文献
3.
Shizhong Geng Xinan Jiao Paul Barrow Zhiming Pan Xiang Chen 《Veterinary microbiology》2014,168(2-4):388-394
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
4.
从病死的鸡、鹅、鸽中分离到3株禽I型副黏病毒(CPMV、GPMV、PPMV)。毒力测定结果显示,CPMV、GPMV的毒力与鸡新城疫病毒(NDV)F48E9株的毒力相似,为强毒型;PPMV的毒力与鸡NDVLaSota株的毒力相似,为自然弱毒株。对该分离株F基因裂解位点的序列分析结果表明,CPMV、GPMVF裂解位点氨基酸序列为112K-R-Q-K-R-F117,符合强毒株的序列特征;PPMV F裂解位点氨基酸序列为112G-R-Q-G-R-L117,属于弱毒株的特征性序列。将该3株病毒制成灭活疫苗,分别免疫鸡,结果都能诱导鸡体产生较高水平的HI抗体;再分别以CPMV、GPMV攻击免疫鸡群,结果显示免疫鸡群可得到保护,而非免疫鸡群被攻击后全部致死。用HI方法检测3株病毒与Lasota株之间的交叉血凝抑制试验,结果表明LaSota与GPMV两毒株间的抗原性无明显差异,LaSota与CPMV、PPMV两毒株间的抗原性有较小的差异。本研究将有助于进一步开展禽Ⅰ型副黏病毒的致病机制和新型疫苗等方面的研究。 相似文献
5.
Marek's disease (MD) is a lymphoproliferative disease of domestic chickens caused by a highly infectious, oncogenic alpha-herpesvirus known as Marek's disease virus (MDV). MD is presently controlled by vaccination. Current MD vaccines include attenuated serotype 1 strains (e.g., CVI988/Rispens), avirulent serotype 2 (SB-1), and serotype 3 (HVT) MDV strains. In addition, recombinant MDV strains have been developed as potential new and more efficient vaccines to sustain the success of MD control in poultry. One of the candidate recombinant MDV strains, named rMd5deltaMeq, was derived from Md5, a very virulent strain of MDV lacking the MDV oncogene Meq. Our earlier reports suggest that rMd5deltaMeq provided protection equally well or better than commonly used MD vaccines in experimental and commercial lines of chickens challenged with very virulent plus (vv+) strains of MDV. In this study, maternal antibody-positive (trial 1) and negative (trial 2) chickens from a series of relatively MD resistant lines were either vaccinated with the rMd5deltaMeq or CVI988/Rispens followed by infection of a vv+ strain of MDV, 648A, passage 10. This report presents experimental evidence that the rMd5deltaMeq protected significantly better than the CVI988/Rispens (P < 0.01) in the relatively resistant experimental lines of chickens challenged with the vv+ strain of MDV. Together with early reports, the rMd5deltaMeq appeared to provide better protection, comparing with the most efficacious commercially available vaccine, CVI988/Rispens, for control of MD in lines of chickens regardless of their genetic background. 相似文献
6.
Twenty-five strains of Escherichia coli isolated from turkeys were characterized for their serum resistance and virulence. An in vitro bactericidal assay was used to determine the serum resistance of E coli. Virulence was determined by survival time after IV inoculation of each strain into 3-week-old turkeys. Serum-resistant E coli strains were generally found to be virulent for turkeys, whereas serum-sensitive E coli strains were avirulent. Of the 25 strains, 18 strains were placed in the 2 categories of serum-resistant/virulent and serum-sensitive/avirulent. Five strains were serum-resistant and avirulent, and 2 strains were serum-sensitive and virulent. Serum resistance appears to be an important determinant of virulence for E coli in turkeys; however, the requirement for other virulence factors, in addition to serum resistance, was suggested by the finding that 5 serum-resistant strains were avirulent in turkeys. 相似文献
7.
Seven field isolates of German origin and the type strain WVU 1853 of Mycoplasma synoviae (MS) were experimentally investigated for their virulence in mycoplasma-free broiler chickens. Two groups of birds were inoculated at 6 days of age with each isolate, one group into the thoracic air sac and the other group intravenously and all surviving birds were examined at necropsy 17 days post inoculation (pi). Groups of negative control birds received sterile Frey's broth medium by intravenous and intra-air sac inoculation, respectively. Variation in virulence was evaluated on the basis of significant differences in incidence, severity and extend of MS-induced airsacculitis and synovitis as well as isolation rates of MS especially from parenchymous organs. All the strains tested were pathogenic but varied in their virulence for broiler chickens. Based on differences of the virulence, the isolates were classified to the categories: (1.) highly virulent, (2.) virulent, (3.) moderately virulent and (4.) slightly virulent. (1) Strains WVU 1853 and 246-91 induced a systemic disease associated with multiple synovitis and bilateral airsacculitis (2) Strains 93-92 and 151-77 induced bilateral airsacculitis similar to WVU 1853 and 246-91 but rarely a systemic disease after exposure by intra-thoracic airsac inoculation. (3) In comparison, strains 27-79, 76-93 and 513-83 caused less frequently airsacculitis and even if, then only at the side of intra-airsac exposure. (4) Strain 91-93 has been found to differ significantly from all the other isolates in its capacity to produce disease independently from the inoculation route. After intravenous inoculation, findings gave no indications for strains with selective tropism to the epithelial membranes of the lower respiratory tract or to those of the joints, tendon sheaths and bursae. However, the presented data of the experiments suggest that the MS strains tested differ in their potential capacity to invade systemically and produce acute septicaemia. 相似文献
8.
A live cholera vaccine was developed from a virulent avian septicemia strain of Pasteurella multocida serotype 1. The virulent parental strain was mutagenized with N-methyl-N'-nitro-N-nitroso guanidine. Mutants were selected that had either smaller colonies at 37 C or temperature sensitivity for growth at 41 C. Four small-colony mutants and 2 temperature-sensitive mutants were studied. All the mutants were avirulent for turkeys. Sixteen days after turkeys were vaccinated with each mutant, both the vaccinates and unvaccinated controls were challenge-exposed to virulent P. multocida of the homologous serotype and the heterologous serotype 3. Two of the small-colony mutant strains protected against both homologous and heterologous challenge. Suggested for a live cholera vaccine is P. multocida M3G, a small-colony-forming mutant, innocuous for both mice and turkeys and stable against reversion. 相似文献
9.
Shivaramaiah S Wolfenden RE Barta JR Morgan MJ Wolfenden AD Hargis BM Téllez G 《Avian diseases》2011,55(2):319-323
Necrotic enteritis (NE) caused by Clostridium perfringens (CP) in poultry is an important bacterial disease in terms of economic implications. The disease is multifactorial and is invariably associated with predisposing factors. In the present experiments, we investigated the potential predisposing role of neonatal Salmonella Typhimurium (ST) infection for NE-associated mortality in a laboratory challenge model. In two experiments, day-of-hatch chicks were randomly assigned to four groups: Group 1, nonchallenged control; Group 2, chickens received Eimeria maxima (EM) and CP; Group 3, chickens received EM and CP and were also challenged with ST at day 1 of age; Group 4, chickens received EM and CP and were also challenged with ST at day 17 of age. Challenged groups received an oral dose of EM at 18 days of age and CP (10(8) colony-forming units/chick) at 22-23 days of age. When compared to EM and CP, chicks challenged with ST (day 1) had increased NE-associated mortality and CP-associated lesion scores (P < 0.05) in both experiments. Furthermore, body weight and body weight gain were lower (P < 0.05) in chicks infected with ST (day 1) in the first experiment, even though no differences (P > 0.05) were observed in weight gain in the second experiment. Chicks challenged with ST (day 17) were similar to the EM and CP group in all of the above-mentioned parameters, indicating that a paratyphoid infection in younger chicks remarkably alters the susceptibility to secondary bacterial infections. Based on this work, the authors suggest that an ST infection early in the age of a chick may be important for altering susceptibility to NE, an observation that may be useful from the perspective of experimental reproduction of this disease and, perhaps, as an economically important reason to address the problem of paratyphoid Salmonella infections in young chicks. 相似文献
10.
为建立评价金黄色葡萄球菌毒力和用于筛选免疫保护性菌株的技术方法,选取小鼠腹腔攻毒方法确定的强毒力和弱毒力菌株各3株,经小鼠后腿肌肉注射不同剂量,比较20 d的临床病变差异,确定小鼠后腿内侧肌肉注射0.25 mL、OD600=0.6的剂量可以评价不同金黄色葡萄球菌的毒力。利用该方法比较了6株强毒力菌株的毒力差异,并用于2株免疫保护性菌株的筛选。结果证明建立的金黄色葡萄球菌毒力评价方法可以精确、客观比较不同菌株毒力差异,并可用于免疫保护性菌株的筛选。 相似文献
11.
Temperature-sensitive (TS) mutants of the S6 strain of Mycoplasma gallisepticum (MG) were used to immunize newly hatched chickens. Immunized chickens developed antibodies to the wild-type (WT) S6 strain as demonstrated by serologic tests. MG was recovered from nasal cavities but not from the lower respiratory tract of the immunized chicks. Three weeks after intranasal immunization, chickens were challenged via the air sacs with the virulent S6 strain. Immunized chickens were significantly better protected from development of air-sac lesions than were controls. 相似文献
12.
Induction of strong protection by vaccination with partially attenuated serotype 1 Marek's disease viruses 总被引：3，自引：0，他引：3
Witter RL 《Avian diseases》2002,46(4):925-937
Studies were conducted to better understand the relationship among Marcek's disease (MD) vaccine strains between induction of protective immunity and the degree of attenuation (or virulence). To obtain viruses at different stages of attenuation, very virulent plus MD strains 584A and 648A and selected clones of these strains were serially passaged in chicken and duck cells. These viruses were considered fully attenuated after passage for 70-100 times in chicken embryo cell cultures until they no longer induced gross lesions in susceptible, maternal antibody-negative (ab-) chickens. Lower passages of the same strains were considered partially attenuated, provided their virulence was less than that of the parent strain. Four of five partially attenuated preparations derived from MD virus strains 584A and 648A or the previously attenuated Md11 strain induced 28%-62% higher levels of protection in maternal antibody-positive (ab+) chickens against virulent MD challenge than the fully attenuated counterpart viruses. The partially attenuated 584A/d2/3 strain replicated in chickens but was totally nonprotective. Data from two subsequent trials in ab+ chickens confirmed that protection induced by the partly attenuated (passage 80) preparations was 79% and 118% higher, respectively, than that induced by the fully attenuated (passage 100) preparations of strain 648A. However, in one trial with ab- chickens, no difference in protection between partially and fully attenuated virus was observed. Strong protection (up to 85%) against highly virulent challenge also was provided by preparations of 648A at passages 40-60, which were moderately oncogenic when used alone. Partially attenuated strains tended to replicate to higher titers in both ab+ and ab- chickens compared with fully attenuated vaccines. Also, ab+ and ab- chickens vaccinated with partially attenuated strains developed three- to nine fold more extensive microscopic lesions in peripheral nerves at 14 and 22 days after virulent challenge than chickens vaccinated with fully attenuated strains. When measured in ab+ chickens, loss of lesion induction by 648A was achieved 30 passages earlier (at passage 70) than when measured in ab- chickens. Thus, maternal antibodies appeared to abrogate the pathogenicity of some partially attenuated strains. These studies establish for MD the principle that at least some partially attenuated MD viruses may replicate better and induce stronger immunity against virulent challenge than fully attenuated preparations of the same strain, at least when tested in ab+ chickens. Moreover, depending on passage level, partially attenuated vaccine strains may be relatively innocuous for ab+ chickens, causing few or no lesions. 相似文献
13.
Shimoji Y Asato H Sekizaki T Mori Y Yokomizo Y 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2002,64(2):173-176
To investigate the role of hyaluronidase in the pathogenicity of Erysipelothrix rhusiopathiae, transposon Tn916 was transferred from Enterococcus faecalis CG110 to a virulent strain of E. rhusiopathiae, and hyaluronidase-deficient mutants were isolated. A virulence assay in the mice showed that of the seven hyaluronidase-deficient mutants tested, six mutants were avirulent, but that one mutant, designated AST121, was as virulent as its parental strain. Western immunoblotting with a monoclonal antibody specific to the capsule, a major virulence factor of the organism, revealed that all of the avirulent mutants had lost the capsular antigen, whereas the mutant AST121 did not. These results suggest that the lack of virulence of the six hyaluronidase-negative mutants could be due to a loss of the capsule and that hyaluronidase does not contribute to the lethality of E. rhusiopathiae infection in mice. 相似文献
14.
Five groups of genetically susceptible chickens were inoculated at hatching with lymphoid leukosis virus; four of these were given infectious bursal viruses of varying virulence at 14 days of age and one group was not inoculated (control). All chickens in the control group developed evidence of lymphoid leukosis by 180 days. Two groups given relatively virulent bursal disease viruses, which destroyed bursal lymphoid cells, did not develop lymphoid leukosis. Treatment with avirulent vaccines had no visible effect on bursal morphology and did not significantly alter the incidence of lymphoid leukosis in two other groups, although the time of development was delayed. Results of our study show that viral-induced destruction of the bursa of Fabricius eliminates the development of lymphoid leukosis but that infection without bursal destruction has little effect on lymphoid leukosis. 相似文献
15.
16.
Kelemen M Forgách K Iván J Palya V Süveges T Tóth B Mészáros J 《Acta veterinaria Hungarica》2000,48(4):443-454
The appearance of very virulent strains of infectious bursal disease (IBD) virus at the end of the 1980s made it necessary to develop more effective immunization procedures. To facilitate this, the immunogenicity and the immunosuppressive effect of a mild (G-87), an intermediate (LIBD) and an intermediate-plus (IBDV 2512) IBDV strain were tested after the in ovo inoculation of 18-day-old SPF and broiler chicken embryos. It was established that no noteworthy difference existed between the immunized and the control embryos in hatching rate and hatching weight. The higher the virulence of the vaccine virus strain, the more severe damage it caused to the lymphocytes of the bursa of Fabricius. In SPF chickens, the haemagglutination inhibition (HI) titres induced by a Newcastle disease (ND) vaccine administered at day old decreased in inverse ratio to the virulence of the IBD vaccine strain, while in broiler chickens this was not observed. Despite the decrease of the HI titre, the level of protection did not decline, or did so only after the use of the 'hot' strain. SPF chickens immunized in ovo with a complex vaccine prepared from strain IBDV 2512 and IBD antibody showed the same protection against Newcastle disease as the broilers. In broiler chicken embryos immunized in ovo, only strain IBDV 2512 induced antibody production, and such chickens were protected against IBD at 3 weeks of age. The complex vaccine administered in ovo has been used successfully at farm hatcheries as well. 相似文献
17.
The pathogenicity of two strains (B4 and C2) of Eimeria mitis was studied using young broiler chickens. Both strains of coccidia were pathogenic, and C2 strain was more virulent than B4. Growth of the broilers was depressed as early as day 3 postinoculation (PI), but the depression was greatest during days 5 and 6 PI. Feed conversion and shank skin pigment of the young broiler chickens were concomitantly affected by infections of E. mitis. Infection subsided by day 7 or 8 PI and was accompanied by a compensatory growth. The drugs effective against the infections were halofuginone, lasalocid, monensin, and nicarbazin. The least efficacious were zoalene and amprolium plus ethopabate. 相似文献
18.
Escherichia coli colonization of the trachea in poultry: comparison of virulent and avirulent strains in gnotoxenic chickens 总被引：5，自引：0，他引：5
In chickens, virulent Escherichia coli strains express their pathogenicity in the respiratory tract. A quantitative comparison of tracheal colonization by virulent and avirulent E. coli was carried out in gnotoxenic chickens after intestinal implantation. Two-week-old axenic chicks reared in isolators were inoculated per os with various associations of identified E. coli strains. No clinical sign of disease was observed in any of the chicks, despite the presence of virulent strains in all the intestines and most of the tracheas. The virulent organism reached greater population sizes in the trachea and feces of monocontaminated chicks and of chicks contaminated simultaneously with a virulent and an avirulent strain. In holoxenic chicks, identified virulent and avirulent strains were outnumbered by the E. coli population of the intestinal flora previously established and could not be recovered from the tracheas of most chicks. 相似文献
19.
To study the replication of classical swine fever virus (CSFV) in cell culture, kinetics of viral plus-strand RNA synthesis, of viral structural and non-structural protein expression as well as of secreted and cell-associated infectious virus were determined. Highly virulent, moderately virulent and avirulent strains that were tested in standardized animal experiments to confirm their virulence were used to search for in vitro parameters allowing the differentiation of strains according to their virulence. No significant qualitative or quantitative differences were found between the strains studied when either RNA replication or protein synthesis were investigated. However, the ratio of cell-associated virus versus secreted virus proved to be considerably lower for the highly virulent strains when compared to avirulent or moderately virulent strains. These data suggest that highly virulent strains of CSFV can be distinguished in cell culture from strains with reduced virulence. 相似文献
20.
Kyung-Woo Lee Hyun S. Lillehoj Seung I. Jang Guangxing Li Sung-Hyen Lee Erik P. Lillehoj Gregory R. Siragusa 《Comparative immunology, microbiology and infectious diseases》2010,33(6):e105-e110
The effect of dietary Bacillus-based direct-fed microbials (DFMs; eight single strains designated as Bs2084, LSSAO1, 3AP4, Bs18, 15AP4, 22CP1, Bs27, and Bs278, and one multiple-strain DFM product [AVICORR™]) on growth performance, intestinal lesions, and innate and acquired immunities were evaluated in broiler chickens following Eimeria maxima (EM) infection. EM-induced reduction of body weight gain and intestinal lesions were significantly decreased by addition of 15AP4 or Bs27 into broiler diets compared with EM-infected control birds. Serum nitric oxide levels were increased in infected chickens fed with Bs27, but lowered in those given Bs2084, LSSAO1, 3AP4 or 15AP4 compared with the infected controls. Recombinant coccidial antigen (3-1E)-stimulated spleen cell proliferation was increased in chickens given Bs27, 15AP4, LSSAO1, 3AP4, or Bs18, compared with the infected controls. Finally, all experimental diets increased concanavalin A-induced splenocyte mitogenesis in infected broilers compared with the nonsupplemented and infected controls. In summary, dietary Bacillus subtilis-based DFMs reduced the clinical signs of experimental avian coccidiosis and increased various parameters of immunity in broiler chickens in a strain-dependent manner. 相似文献