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1.
The efficacy of a muramidase-released protein (MRP) and extracellular factor (EF) vaccine in preventing infection and disease in pigs challenged either with a homologous or a heterologous Streptococcus suis serotype 2 strain (MRP+EF+) was compared with the efficacy of a vaccine containing formalin-killed bacterin of S. suis serotype 2 (MRP+EF+). The enhancement of the immune response by different adjuvants (a water-in-oil emulsion [WO] and an aluminium hydroxide-based adjuvant [AH]) and their side effects were also studied. The MRP and EF were purified by affinity chromatography. Pigs were vaccinated twice at three weeks and six weeks of age and challenged intravenously with virulent S. suis serotype 2 strains (MRP+EF+) at eight weeks of age. At challenge, the pigs vaccinated with MRP+EF/WO had high anti-MRP and anti-EF titres and were protected as effectively as pigs vaccinated with WO-formulated vaccines with bacterin. Eight of the nine pigs survived the challenge and almost no clinical signs of disease were observed. The titres obtained with the MRP+EF/AH vaccine were low and only two of the five pigs were protected. Pigs vaccinated with either MRP or EF were less well protected; three of the four pigs died after challenge but the clinical signs of disease were significantly less severe than those observed in the placebo-vaccinated pigs. The protective capacity of the bacterin/AH vaccine was very low, and the mortality among these pigs was as high as in the placebo-vaccinated pigs (80 per cent). Postmortem histological examination revealed meningitis, polyserositis and arthritis in the clinically affected pigs. The results demonstrate that a subunit vaccine containing both MRP and EF, formulated with the WO adjuvant, protected pigs against challenge with virulent S. suis type 2 strains.  相似文献   

2.
A total of 142 strains from different serotypes of Streptococcus suis isolated in Spain from diseased pigs (88 strains) and healthy carrier pigs (54 strains) were studied for the presence of a muramidase released protein (MRP) and an extracellular factor (EF). The following five phenotypes: MRP+EF+, MRP+EF-, MRP-EF+, MRP+EF* and MRP*EF- were detected. A high percentage of S. suis serotype 2 strains isolated from diseased pigs (84 per cent) belonged to phenotype MRP+EF+, but this phenotype has also been noticed in other serotypes (serotypes 1, 1/2 and 14). Both proteins were detected in S. suis serotype 2 strains (26%) isolated from healthy carrier pigs and one of both proteins in serotypes 1 and 14 (phenotype MRP+EF*). The isolation of S. suis strains from healthy pigs which have shown both proteins may support the epidemiological significance of these carriers in the maintenance, transmission and distribution of virulent strains within and between swine farms.  相似文献   

3.
Streptococcus suis (Sc. suis) can cause very different clinical entities. In contrast to Sc. suis-associated pneumonia, the induction of meningitis, septicemia, and polyarthritis by certain Sc. suis strains requires the expression of virulence factors that contribute to the invasiveness of the pathogen. In the presented study, we examined the occurrence of known virulence-associated factors in Sc. suis isolates from samples sent to the Institute of Microbiology, School of Veterinary Medicine Hannover, in order to evaluate their significance as potential virulence factors in different disease complexes in Northern Germany. The results show that (i) MRP + EF + serotype 2 and MRP* EF-serotype 9 strains are statistically significant associated with the disease complex meningitis/septicemia/arthritis and, thus, have to be considered invasive strains, (ii) serotyping alone is not sufficient for identification of virulent strains, (iii) there is a remarkable heterogeneity among pneumonia-associated Sc. suis strains and (iv) activity of haemolysin or suilysin appears to be not appropriate as virulence marker. Finally, it has to be noted that at present only half of the Sc. suis isolates from pigs with meningitis/septicemia/poyarthritis can be characterised by the detection of virulence-associated factors. Thus, the identification and characterisation of additional, serotype independent virulence factors of Sc. suis is a very important issue in future studies.  相似文献   

4.
The present study describes the prevalence of muraminidase-released protein (MRP) and extracellular factor (EF) proteins associated with virulence of Streptococcus suis serotype 2 from a collection of USA strains. Sixty-six strains belonging to serotypes 1, 2, 3, 4, 7, and 10, were analyzed with a set of double antibody sandwich ELISAs and Western blots. Nineteen of 34 serotype 2 strains from cases of swine meningitis had the MRP+EF+ phenotype. Five of 7 serotype 2 strains isolated from lungs had an MRP*EF- phenotype. An MRP-EF+ phenotype was found in 4/34 strains isolated from swine meningitis. The MRP*EF- and MRP-EF+ phenotypes have not been reported previously. All strains of serotypes other than 2, including isolates from cases of meningitis, had the MRP-EF- phenotype, suggesting that these strains must have other, as yet undetected, virulence factors.  相似文献   

5.
Streptococcus suis strains (n=411), isolated from diseased pigs in seven European countries were serotyped using specific antisera against serotype 1 to 28, and were phenotyped on the basis of their muramidase-released-protein (MRP) and extracellular-factor protein (EF) production. Overall, S. suis serotype 2 appeared to be most prevalent (32%), followed by serotype 9 (20%) and serotype 1 (12%). Serotype 2 was most frequently isolated in France, Italy and Spain, whereas serotype 9 was most frequently isolated in Belgium, The Netherlands and Germany. In the United Kingdom serotypes 1 and 14 were most frequently isolated. High percentages of S. suis serotype 1, 2, 1/2 and 14 strains, isolated from tissues associated with S. suis infections such as brain, serosa, joint, heart and organs expressed the EF-protein, indicating that in these serotypes expression of EF is likely to be associated with virulence. In contrast, strains belonging to serotype 7 and 9, isolated from tissues associated with S. suis infections did not produce EF. These results strongly suggest that in the serotypes 7 and 9 EF expression is not related to virulence. More than 80% of the S. suis serotype 9 strains produced an MRP* protein, a high molecular variant of the 136kDa MRP. Expression of MRP* in serotype 9 strains is possibly associated with virulence.  相似文献   

6.
Virulence-associated gene profiling of Streptococcus suis isolates by PCR   总被引：11，自引：0，他引：11  
Definition of virulent Streptococcus suis strains is controversial. One successful approach for identification of virulent European strains is differentiation of capsular serotypes (or the corresponding cps types) and subsequent detection of virulence-associated factors, namely the extracellular factor (EF, epf), the muramidase-released protein (MRP, mrp) and the hemolysin suilysin (SLY, sly). In this work we present a novel multiplex PCR (MP-PCR) and an mrp variant PCR for identification and characterization of virulent S. suis strains. These new methods were used to identify association of disease with particular profiles of virulence-associated genes. The MP-PCR allowed identification of S. suis through detection of the housekeeping gene gdh, differentiation of four cps types (1, 2, 7 and 9), and detection of epf, mrp, sly and arcA (arginine deiminase from S. suis). Furthermore, this study describes the first PCR assay for differentiation of at least six mrp variants. Expression of the corresponding size variants of MRP was shown for four of the six mrp variants, but was undetectable for the two larger mrp variants in the particular strains investigated. The results of this study suggest that cps7 strains are associated with pneumonia and that variation of mrp is very pronounced among these strains. Gene profiles of invasive, pneumonia and carrier S. suis isolates by combination of PCR assays allowed differentiation of 24 different genotypes among cps1, 2, 7 and 9 strains. Forty-five percent of the invasive S. suis diseases investigated in this study were caused by only two of these genotypes, namely cps2/mrp+/epf+/sly+ and cps9/mrp(*)/epf-/sly+. Thus, this study demonstrates for the first time a uniform profile of the particular virulence-associated genes for the vast majority of the investigated invasive cps9 strains.  相似文献   

7.
Two cases of meningitis due to Streptococcus suis in humans are reported here. A butcher and an abattoir worker were referred to a health centre in Castellón (Spain) with fever and symptoms of meningitis. After adequate treatment, a slight hipoacusia persisted as sequelae in both cases. Colonies of S. suis group R, serotype 2 and phenotype MRP+EF+ were isolated from cerebroespinal fluid. Epidemiological studies showed that both workers had in common the handling of pork meat of slaughtered healthy pigs from three closed farms. A study of the tonsils from apparently healthy, slaughtered pigs was carried out. A total of 234 tonsillar samples were obtained and 81 strains of S. suis were isolated from them. Serotype 2 appeared to be the most frequent (50.6%), and the analysis for phenotype showed a high percentage of tonsillar strains with the phenotype MRP+EF+ (35.9%). The humans and 28 tonsillar swine strains showed a similar profile (S. suis group R, serotype 2 and phenotype MRP+EF+). A total of 26 of the swine isolates were analysed by ribotyping using EcoRI. The human strains showed the same six-band hybridization pattern that shared five bands with the pattern most frequently shown by most of the tonsillar N. suis group R, serotype 2 and phenotype MRP+EF+ strains, differing only in the lightest, faintest band which was slightly less anodical in human (> or = 1.8 kb) than in swine (approximately 1.8 kb). From these results, both groups of strains, humans and porcine, showed differences; how can these differences in the pattern of ribotyping be explained if they should have the same origin? Is it possible that they have undergone an adaptation to the new host or perhaps the modification is due to other unknown causes? Further studies in this area are required in order to answer these questions.  相似文献   

8.
We developed a PCR assay for the rapid and sensitive detection of virulent Streptococcus suis type 2 and highly virulent S. suis type 1 in tonsillar specimens from pigs. The PCR primers were based on the sequence of the gene encoding the EF-protein of virulent S. suis type 2 strains (MRP+EF+) and highly virulent S. suis type 1 strains (MRP(s)EF+) and of the EF protein of weakly virulent S. suis type 2 strains (MRP+EF). The latter strains give rise to larger PCR products than the virulent strains of S. suis type 1 and 2. A positive control template was included in the assay to identify false negative results. The PCR was evaluated using tonsillar specimens from herds known (or suspected) to be infected and herds without an S. suis history. The results obtained with the PCR assay were compared with the results obtained with a newly developed bacteriological examination. In this bacteriological examination we were able to identify the EF-positive strains directly in the tonsillar specimens. From the 99 tonsils examined, 48 were positive in the PCR and 51 negative. All specimens from which EF-positive S. suis strains were isolated were also positive in the PCR assay. Three samples were positive in the PCR, but negative by bacteriological examination. The results demonstrated that the PCR is a highly specific and sensitive diagnostic tool for the detection of pigs carrying virulent strains of S. suis type 2 and highly virulent strains of type 1. Application of the assay may contribute to the control of S. suis infections.  相似文献   

9.
猪链球菌2型四川分离株毒力基因的检测及其序列分析   总被引：1，自引：0，他引：1  
根据猪链球菌2型的MRP、EPF和SLY基因设计合成了四对引物,对我们分离鉴定的2005四川分离株进行毒力因子检测,并对阳性产物测序比较。结果以分离株为模板,获得了与预期结果一致的867bp(MRP)、572bp(EF)的2个片段,以及SLY的长度为1502bp目的片段(外引物)和1443bp的目的片段(内引物)。说明分离株SSsc0501为MRP+EF+SLY+,属于具有3种主要毒力因子的强毒株。经对PCR阳性产物测序及序列分析,结果其与P1/7株的核苷酸序列完全一致,与1933株的同源性达99.7%,仅在128位、217位、744位、1380位、1386位的5个核苷酸发生突变。在氨基酸水平上SSsc0501株与1933株的同源性达99.6%,有2个氨基酸发生替代。  相似文献   

10.
The production of muramidase-released protein (MRP), extracellular protein factor (EF) and hemolysin (suilysin) by 101 Canadian field strains of Streptococcus suis capsular type 2 is described. Most strains (72%) isolated from diseased pigs were MRP-EF- and only 1 strain was MRP+EF+. This strain was also the only 1 to produce the hemolysin. Thirteen strains (15%) were MRP+ EF- and only 3 strains were MRP* EF-. All the strains isolated from clinically healthy pigs as well as a bovine and 2 human isolates had a MRP-EF- phenotype. In addition, 7 strains (8%) had a MRPS phenotype, which had so far been described for S. suis capsular type 1. In conclusion, most Canadian field isolates of S. suis capsular type 2 tested in this study do not produce the virulence-related proteins described so far for this bacterial pathogen.  相似文献   

11.
致病性猪链球菌2型的病原分离鉴定及毒力因子的PCR检测   总被引：6，自引：3，他引：3  
通过对广西某猪场急性死亡的猪进行病原分离,分离到革兰氏阳性球菌,用链球菌快速鉴定试剂条Rapid ID 32 Strep鉴定为猪链球菌2型;并对分离菌进行猪链球菌2型荚膜多糖抗原（cps2J）及其重要毒力因子溶菌酶释放蛋白（MRP）、细胞外蛋白因子（EF）和溶血素（SLY）的多重PCR检测,同时对cps2J基因进行序列测定,与GenBank发表的猪链球菌2型相比,同源性为98.8%,毒力因子MRP、EF和SLY检测均为阳性,证实广西某猪场急性死亡的猪为高毒力猪链球菌2型感染所致。动物试验中,该菌可引起小白鼠部分死亡,家兔体温最高升至40.3℃,最后败血而死。  相似文献   

12.
Streptococcus suis diseases in pigs, most importantly meningitis, are worldwide responsible for major economic losses in the pig industry. About one fourth of invasive S. suis diseases are caused by S. suis serotype 9 strains in Europe. However, little is known about serotype 9 since most studies were performed with serotype 2. The objective of this study was to determine the immunogenicity and protective efficacy of a serotype 9 bacterin in piglets. Challenge was conducted with a reference serotype 9 strain, belonging to the same clonal complex but to a different sequence type as the bacterin strain. The bacterin induced protection against mortality but not morbidity. Eleven days post infection, 3 of 7 vaccinated survivors were not fully convalescent and had not eliminated the challenge strain from inner organs completely. In accordance with the clinical findings, the majority of piglets showed fibrinous-suppurative lesions in at least one inner organ or tissue. In contrast to the placebo group such lesions were not detected in one third of bacterin-vaccinated piglets. Determination of specific serum IgG titers revealed that the bacterin elicited seroconversion against muramidase-released protein and basic membrane lipoprotein. Furthermore, vaccination was associated with induction of opsonizing antibodies against the serotype 9 challenge strain. However, titers of opsonizing antibodies were rather low in comparison to those found in our previous serotype 2 vaccination trial. Piglets developed substantially higher titers of opsonizing antibodies after challenge. Opsonizing antibodies were absorbable with the serotype 9 challenge strain but not with an unencapsulated isogenic mutant of a serotype 2 strain indicating their specificity. The results indicate that a serotype 9 bacterin is less protective than a serotype 2 bacterin, most likely due to inducing only low titers of opsonizing antibodies. This might contribute to emergence of serotype 9 strains, in particular strains of this clonal complex, in Europe.  相似文献   

13.
A standardized model of Streptococcus suis type 2 infection in specific-pathogen-free piglets, housed in high-security barns, was used to compare the virulence of 3 French field strains of S. suis serotype 2 isolated from tonsils of a healthy pig (strain 65) or from diseased pigs (meningitis, strain 166', or septicemia, strain 24). In one of the 2 trials, 7-week-old pigs, in 3 groups of 8, were inoculated intravenously with 2 x 10(8) colony-forming units of S. suis type 2. In each group, 1 uninfected animal was a sentinel. Eight animals were also used as negative control group. The experiment was repeated under similar conditions with strains 65 and 166'. Virulence differed markedly among these S. suis strains when clinical signs, zootechnical performances, lesions, and bacteriological data were analyzed. Strain 65 did not induce clinical signs in inoculated pigs. In contrast, pigs infected with the other 2 strains exhibited clinical signs and typical lesions of S. suis type 2 infections. Differences in virulence were also observed between the 2 virulent strains. Sentinel animals exhibited the same manifestations as those recorded in inoculated piglets. Results were similar in the second trial, indicating that under the present experimental conditions, results were reproducible. The standardized conditions described in this study could be a useful tool to further study about the S. suis infection.  相似文献   

14.
The effect of vaccination with a killed whole-cell vaccine of extracellular factor-positive Streptococcus suis serotype 2 (S suis 2 EF(+)) combined with medication with amoxicillin on the presence of virulent S suis 2 EF(+) strains on the tonsils of sows and their offspring was evaluated. In two herds, 14 pregnant sows that carried these virulent strains, as detected by PCR in three consecutive tonsillar brush samples, were selected and randomly assigned to be treated or left untreated as controls. The treated sows were vaccinated at six and three weeks before the expected farrowing date and medicated from one week before expected farrowing until the end of the experiment. Two weeks before parturition, the sows were housed in individual isolation farrowing rooms, and the sow and its litter were sampled by using tonsil brushes and tonsil swabs, respectively. Approximately 27 days postpartum, the sows and their piglets were euthanased and their tonsils were collected and analysed by pcr. No S suis 2 EF(+) could be detected in the tonsils of the seven treated sows, but the tonsils of the seven untreated sows remained positive. Only one of the litters of the untreated sows became infected, five days after birth, and none of the litters of the treated sows became infected.  相似文献   

15.
A total of 323 isolates of Streptococcus suis recovered from diseased or healthy pigs in France were serotyped. The presence of virulence-related proteins, Muraminidase-Released Protein (MRP), Extracellular Factor (EF) and Suilysin was also studied in 122 isolates of capsular types 2, 1/2, 9, 7 and 3 to evaluate their implication in virulence of S. suis. Capsular types 2, 1/2, 9, 7 and 3 were the most frequently detected (93%), with 69% for the capsular type 2 alone. Capsular types 2, 1/2, 9, 7, 3, 1, 4, 8, 18, 10 and 12 were isolated from diseased pigs, whereas types 2, 7, 9, 1/2, and 3 originated from the nasal cavities or tonsils of healthy animals. Most of the S. suis type 2 isolates recovered from diseased pigs carried MRP+ EF- Suilysin- (46%) or MRP+ EF+ Suilysin+ (28%) phenotypes. The MRP+ EF- Suilysin- phenotype was also detected in 67% of S. suis type 2 strains isolated from healthy pigs. The production of the virulence-related proteins was less frequently found in S. suis types 1/2, 9, 7 and 3 recovered either from diseased or healthy pigs. In this study, all the capsular type 1/2 strains were MRP+ EF- Suilysin- and all the S. suis type 7 harboured an MRP- EF- Suilysin- phenotype. The MRP- EF- Suilysin- phenotype was found in S. suis types 2, 3, 7 and 9 isolated from septicaemia, meningitis, pneumonia, and pleurisy. These results suggest that the presence of these proteins should not be used as a single condition for classifying the virulence of a field isolate in France.  相似文献   

16.
The objective of this study was to determine the capsular serotypes and potential virulence factors of Streptococcus suis isolated from pigs with polyserositis. Among the 24 isolates evaluated, serotype 3 [7 (29%) of the isolates] and serotype 4 [5 (21%)] were the most common. The isolates were also studied for the presence of the genes mrp, epf, and sly, which encode muramidase-released protein (MRP), extracellular factor (EF), and suilysin (SLY), respectively. Of the 24 isolates, 8 carried mrp: 4 of serotype 3, 2 of serotype 2, and 2 of serotype 4. One mrp(+) isolate (serotype 2) also carried the epf gene. All 24 isolates carried the sly gene. The serotype and genotype distribution greatly differed from that reported for isolates from pigs with other clinical manifestations of S. suis infection in other countries.  相似文献   

17.
Adherence of Streptococcus suis to porcine endothelial cells   总被引：3，自引：0，他引：3  
Streptococcus suis can cause invasive diseases in pigs and humans, such as meningitis or arthritis. Adherence to and invasion of endothelial cells might represent important steps in survival and spread of S. suis within the host. We tested in vitro adherence and invasion of S. suis strains using a porcine brain microvascular and aortal endothelial cell line. Four S. suis strains were tested with and without prior treatment with porcine serum containing anti-S. suis antibodies. Strains included a capsular serotype 2 strain and its non-encapsulated isogenic mutant strain, as well as two non-typeable (NT) strains, which expressed no capsule under our experimental conditions. Strains adhered to both cell lines to different extents depending on encapsulation and pre-treatment with porcine immune serum. The serotype 2 strain showed almost no adherence, whereas the non-encapsulated mutant strain adhered strongly. Similarly, both NT strains adhered substantially better than the serotype 2 strain. Pre-treatment of bacteria with porcine serum increased adherence of the encapsulated serotype 2 strain and decreased adherence of the non-encapsulated strains. None of the strains was able to efficiently invade either of the two cell lines, except for one NT strain, which showed a very low extend of invasion. Our results suggest that S. suis can adhere to but not invade porcine endothelial cells, and that this interaction may involve different bacterial surface structures, such as capsular polysaccharides and/or binding sites for serum components.  相似文献   

18.
Three swine commercial farms with high mortality rates in nursery pigs due to Streptococcus suis serotype 2 were studied. Brain samples from diseased animals were collected for a period of 6 to 10 mo and used to isolate the strain that was responsible for the mortality (virulent strain) in each farm. Tonsil swabs from piglets at 5, 10 and 15 d were taken to assess both total colonization and colonization by the virulent strain. The effect of sow vaccination against S. suis on colonization was evaluated in 1 of the farms. All suspect tonsil isolates were identified biochemically and then tested against serotype 2. The genomic patterns of serotype 2 isolates were compared to that of the virulent strain using Rep-PCR. Results showed that total colonization by S. suis occurred very early in the pigs' life, with most animals being colonized by weaning age. Prevalence of colonization by serotype 2 strains was much lower than total colonization. After comparing serotype 2 isolates with the virulent strains, only 1 tonsillar isolate had the same genomic pattern as the virulent strain and it belonged to a 4-week-old weaned pig. The genomic pattern of the virulent strain was not found in any tonsillar isolate from 15-day-old or younger pigs. Although limited by sample size, sow vaccination against S. suis increased total colonization at the same time significantly decreasing colonization by serotype 2 strains. Even though most pigs are colonized early in age by S. suis, colonization by the virulent strain is of low prevalence and delayed in time. This could constitute a risk factor for developing the disease later in time, because animals would be colonized when maternal immunity is no longer present, allowing the organism to become systemic.  相似文献   

19.
Streptococcus suis is a major cause of meningitis, sepsis and arthritis in piglets and a zoonotic agent. Survival in the blood circulation system represents a major step in pathogenesis of S. suis infections. To get further insights into the mechanisms of S. suis survival in the host, we compared a highly virulent S. suis serotype 2 strain with its non-encapsulated and suilysin-deficient mutants in their abilities to resist phagocytosis and killing by polymorphonuclear neutrophils (PMNs) and mononuclear cells. PMNs displayed a higher capacity to take up encapsulated bacteria than mononuclear cells, whereas both cell types internalized efficiently non-encapsulated S. suis. Differentiation of extracellular and intracellular survival of the WT strain revealed that in PMNs the majority of the cell-associated streptococci were intracellular, whereas in mononuclear cells the majority remained attached to the cell surface. S. suis survived mainly extracellularly, since both cells killed intracellular bacteria to a similar extent. As a consequence of different resistance to phagocytosis, only the encapsulated S. suis strains survived co-cultivation with PMNs. Comparison of the WT strain with its encapsulated suilysin-deficient mutant revealed reduced survival of the mutant after co-cultivation with PMNs. Involvement of suilysin in inhibition of phagocytosis was further confirmed by the use of anti-suilysin antibodies and recombinant suilysin. Kinetic experiments with PMNs suggested that reduced survival of the mutant strain was mainly associated with an increased uptake, whilst both strains adhered similarly. Concluding, our results indicate that the capsule and the suilysin play important roles in S. suis survival in the host by interfering with phagocytic uptake.  相似文献   

20.
猪链球菌2型毒力因子研究进展   总被引：2，自引：1，他引：1  
猪链球茵(SS)病是一种严重危害养猪业的人畜共患病,呈世界性分布.根据荚膜抗原特性的不同,猪链球茵被分为35个血清型(1/2型,1型～34型),其中以猪链球菌2型(SS2)流行最广,毒力最强.SS2主要的毒力因子有溶菌酶释放蛋白、胞外蛋白因子、荚膜抗原、溶血素等.然而,新近发现的一些与SS2致病性相关的基因序列和蛋白片段已经成为当前研究的重点和热点.在基因水平上的新发现主要有orf2毒力因子、89 kb毒力岛、转录调节因子、氨基酸通透酶、ABC转运子及表面锚定蛋白基因、反应调节因子RevS基因、纤连蛋白结合蛋白基因、编码噬茵体的基因序列Ssl和分泌性核酸酶SsnA基因等.蛋白水平上的新发现主要有脂磷壁酸的D-丙氨酰位点、自溶素、精氨酸脱亚氨酸酶系统、浑浊因子,38,45,39,44 ku蛋白,以及一些蛋白酶和纤维蛋白溶血酶原受体等.  相似文献   

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