猪链球菌检测及猪链球菌病防治的研究进展

猪链球菌（Streptococcus suis）能引起猪的脑膜炎、心内膜炎、关节炎、肺炎和败血症，并能感染人，是一种重要的人畜共患病病原。国内外许多学者致力于该菌的致病性、快速准确诊断技术以及综合防治研究。本文对猪链球菌的毒力因子、检测方法和疾病防治等方面的研究进展进行了综述。     

猪链球菌病研究进展

链球菌是一种重要的猪病原菌并能感染人 ,它能引起猪的败血症、脑膜炎、肺炎、多发性关节炎和多发性浆膜炎。文章从流行病学、病原及其毒力因子等方面作了详细的综述 ,初步探讨了猪链球菌病的治疗方法     

Streptococcus suis infections in humans: the Chinese experience and the situation in North America

Infections caused by Streptococcus suis are considered a global problem in the swine industry. In this animal species, S. suis is associated with septicemia, meningitis, endocarditis, arthritis and, occasionally, other infections. Moreover, it is an agent of zoonosis that afflicts people in close contact with infected pigs or pork-derived products. Although sporadic cases of S. suis infection in humans have been reported, a large outbreak due to S. suis serotype 2 emerged in the summer of 2005 in Sichuan, China. A similar outbreak was observed in another Chinese province in 1998. Symptoms reported in these two outbreaks include high fever, malaise, nausea and vomiting, followed by nervous symptoms, subcutaneous hemorrhage, septic shock and coma in severe cases. The increased severity of S. suis infections in humans, such as a shorter incubation time, more rapid disease progression and higher rate of mortality, underscores the critical need to better understand the factors associated with pathogenesis of S. suis infection. From the 35 capsular serotypes currently known, serotype 2 is considered the most virulent and frequently isolated in both swine and humans. Here, we review the epidemiological, clinical and immunopathological features of S. suis infection in humans.     

人感染猪链球菌2型的研究进展

猪链球菌2型是一种重要的人畜共患病原菌,可引起人的脑膜炎、败血症等疾病.2005年6月发生的四川疫情是由猪链球菌2型引起的人猪共同感染,流行广,发展快,人猪患病数量多.本文从病原、流行特点、感染途径、临床表现、实验室鉴定(包括培养特性、形态特征、生化特性、血清凝集、毒力基因)等方面做了详细的综述,初步探讨了2型猪链球菌病的防治方法.     

猪链球菌2型CPS2J基因PCR检测技术研究进展

猪链球菌广泛存在于自然界,可引起猪链球菌病,以发烧、败血症、脑膜炎、肺炎、关节炎等为主要特征;猪链球菌病是一种重要的人畜共患传染病,共有35种血清型,其中以2型流行最广,危害最大。荚膜多糖抗原作为链球菌重要毒力因子,在引起猪链球菌病的过程中起到了关键性的作用,以此作为目的基因的PCR检测方法的报道也不在少数,现就近年来国内外猪链球菌2型荚膜多糖抗原基因（CPS2J）PCR检测技术进行综合论述,以期为实验室检测人员提供有关的资料。     

Infection with Streptococcus suis serotypes 1 and 2 in the same diseased pig

Streptococcus suis is an important pig pathogen which is associated with respiratory problems, meningitis and less fre-quently with a variety of other conditions(Hommez et al. 1986). S. suis type 1 causes disease mainly in 1–2 week old pigs while serotype 2 is found commoaily in 2–22 week old pigs, S. suis type 2 is a zoonosis. It can cause meningitis and septicaemia in man (Christensen & Kronvall 1985). Several other serotypes of S. suis have also been identified on the basis of the capsular poly-saccharide (Perch et al. 1983, Hommez et al. 1986). We present a case where we isolated S. suis types 1 and 2 from the brain and lungs respectively of the same diseased suckling piglet. This i/s the first reported case of S. suis types 1 and 2 in Finland.     

Occurrence and diagnostic relevance of virulence-associated factors in Streptococcus suis

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.     

Disruption of srtA gene in Streptococcus suis results in decreased interactions with endothelial cells and extracellular matrix proteins

Streptococcus suis, a major pathogen of swine, is an emerging zoonotic agent which causes meningitis and septic shock. In this study, we investigated the ability of S. suis mutant strain (SRTDeltaA) lacking the sortase A gene (srtA) to interact with host cells and extracellular matrix (ECM) proteins, as well as its virulence in a mouse infection model. We demonstrated that mutant SRTDeltaA had reduced capacity to adhere to and invade porcine brain microvascular endothelial cells compared to the wild-type strain. In addition, mutant SRTDeltaA also showed significantly less adherence to plasma fibronectin, cellular fibronectin and collagen type I. However, disruption of srtA had little effect on the virulence of S. suis in a mouse intraperitoneal model of infection. These results indicate that surface proteins anchored by sortase A are required for a normal level of bacterial binding. However, other factors may also be important for S. suis virulence and interaction with host tissues.     

Purification and characterization of the subtilisin-like protease of Streptococcus suis that contributes to its virulence

Streptococcus suis is a major swine pathogen that is responsible for severe infections such as meningitis, endocarditis, and septicemia. S. suis is also recognized as a zoonotic agent and expresses several virulence factors. The recently identified subtilisin-like protease (SspA) of S. suis plays an important role in the pathogenicity of this bacterium in animal models. The objective of the present study was to clone, purify, and characterize the SspA of serotype 2 S. suis P1/7. The SSU0757 gene encoding SspA was amplified and a 4798-bp DNA fragment was obtained. It was cloned into the expression plasmid pBAD/HisB and then inserted into Escherichia coli to overproduce the protein. The recombinant protease was purified by chromatography procedures and showed a molecular weight of 170 kDa by SDS-PAGE. Its activity was optimal at pH 7 and at temperatures ranging from 25°C to 37°C. It had a high specificity for the chromogenic substrate succinyl-Ala-Ala-Pro-Phe-pNa while specific inhibitors of serine proteases inhibited its activity. In addition to degrading gelatin, the protease hydrolyzed the Aα chain of fibrinogen, which prevented fibrin formation by thrombin. The recombinant subtilisin-like protease also showed toxicity towards brain microvascular endothelial cells. Lastly, sera from pigs infected with S. suis reacted with the recombinant SspA, indicating that it is produced during infections. In conclusion, the SspA of S. suis shared similarities with subtilisin-like proteases produced by other pathogenic streptococci and may contribute to the pathogenic process of S. suis infections.     

猪链球菌2型感染猪和人的现状及研究进展

猪链球菌2型可引起人和猪的感染,甚至死亡,是一种严重的人兽共患病病原,其引起的疫病在我国被列为二类疫病。它能引起仔猪脑膜炎、支气管肺炎、败血症、关节炎及人的化脓性关节炎、眼内炎和心内膜炎等。在世界上许多国家和地区广泛分布,已发现的致病因子有十多种,但致病机理尚未彻底阐明。由于该菌引起的疫病危害性大,所以对该菌的快速诊断检测和防治方法也在不断改进。论文对猪链球菌2型病的流行状况、致病性、检测方法、防治等研究现状进行综述。     

猪链球菌2型毒力相关因子的研究进展

目前,猪链球菌(Streptococcus suis)病已成为严重影响各国养猪业发展和人类健康的一种重要的人兽共患传染病。猪链球菌的血清型众多,有35个血清型,其中猪链球菌2型(Streptococcus suistype 2,SS2)的致病性强、流行范围广,而且它的毒力因子在该菌的致病过程中发挥着重要的作用。但是猪链球菌2型毒力因子认识的缺乏是制约该病有效防制的关键,因此作者对SS2已发现的毒力因子和新发现的一些毒力相关因子进行了广泛深入的论述,为该病的预防、治疗提供科学依据和参考。     

Intracellular invasion and persistence: survival strategies of Streptococcus suis and Mycobacterium avium ssp. paratuberculosis

Streptococcus (S.) suis and Mycobacterium avium ssp. paratuberculosis (MAP) differ substantially in their host specificity and tissue tropism. S. suis is a facultative pathogen in swine, which mainly colonises the upper respiratory tract and can cause meningitis, septicemia, arthritis and pneumonia. In contrast, MAP is an obligatory pathogen causing paratuberculosis in ruminants, and shows high tropism for the intestinal tract. Both pathogens are able to invade and persist in host cells. In S. suis, the significance of invasion for pathogenesis is a matter of controversial discussions. In vitro it has been shown that S. suis is internalized by epithelial cells and survives intracellularly for at least 24 h. However, at present there is no evidence that S. suis invades epithelial cells also in vivo. In MAP, on the other hand, persistence in macrophages is generally considered a crucial step in pathogenesis, but it remains to be elucidated, how it contributes to pathophysiology of the disease. The two pathogens exemplify how intracellular invasion and persistence might play different roles in pathogenesis. In S. suis, intracellular life may represent only a transient retreat phase, whereas in MAP it is the predominant in vivo niche of the pathogen.     

Characterization of the invasion of porcine endothelial cells by Streptococcus suis serotype 2

Streptococcus suis serotype 2 is an important swine pathogen associated mainly with meningitis. In a previous study, we demonstrated the ability of S. suis serotype 2 to adhere to and invade immortalized porcine brain microvascular endothelial cells (PBMECs) forming the blood-brain barrier. The aim of the current work was to further characterize the mechanism(s) by which S. suis invades porcine endothelial cells. The ability of several S. suis strains to interact with PBMECs was not found to correlate with their geographic origin, virulence, host of origin, or suilysin production. Characterization studies demonstrated that proteinaceous adhesins/invasins, cell wall components, lipoteichoic acid, and serum components (including fibronectin) were involved in interactions between S. suis and PBMECs. In addition to PBMECs, S. suis was able to adhere to and invade 2 porcine aortic endothelial cell lines and primary PBMECs.     

Prevalence of various phenotypes of Streptococcus suis isolated from swine in the U.S.A. based on the presence of muraminidase-released protein and extracellular factor.

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.     

Streptococcus suis serotypes associated with disease in weaned pigs

Streptococcus suis was recovered from 9 outbreaks of septicaemia and meningitis in weaned pigs between 1979 and 1983. Fifteen isolates from 7 outbreaks were identified as S. suis type 9, and 3 isolates from 2 outbreaks as S. suis type 2. Three further isolates of S. suis type 2 and an isolate of S. suis type 3 were recovered from cases of bronchopneumonia in weaned pigs from 4 other piggeries.     

Streptococcus suis isolated from pigs in Finland

A total of 58 Streptococcus suis strains were isolated from deceased pigs submitted to the National Veterinary Institute, Regional Laboratory in Kuopio, Finland, over a 3 1/2 year period, most frequently from cases of pneumonia. The bacteria were isolated from cases of meningitis, sepsis, rhinitis, endocarditis and abortion. S. suis was also isolated from nasal cavity, lung and brain of some sick piglets without signs of inflammation. Further S. suis was detected in 12 out of 107 tonsils of healthy fatteners tested. S. suis strains were identified by biochemical methods followed by typing. The most common capsular types were 7, 3 and 2, respectively. Only one type 1 strain and no types 6 and 9 strains were found. All S. suis strains tested were sensitive to penicillin and ampicillin.S. suis is not uncommon in Finnish pig herds. S. suis may be regarded as a potentially pathogenic organism which under certain predisposing conditions may cause serious disease.     

Porcine eperythrozoonosis: from Eperythrozoon suis to Mycoplasma suis

Mycoplasma suis (formerly known as Eperythrozoon suis ) is the most prevalent agent causing haemolytic anaemia in swine. The disease is also known as porcine eperythrozoonosis. M.suis is a small, pleomorphic bacteria parasitizing porcine erythrocytes. To date, no in vitro cultivation system for M.suis has been established and, therefore, our knowledge about the characteristics of M.suis and the pathogenesis of porcine eperythrozoonosis is rather limited. M.suis can cause acute disease, but the major significance of M.suis infections lies in the fact that M.suis can establish chronic and persistent infections leading to a higher susceptibility to other infections, especially of the respiratory and digestive tracts. The present article summarizes the current knowledge of the pathogen, the clinical signs and pathogenesis, diagnostic as well as therapy and prophylaxis.     

The role of toll-like receptors in the pathogenesis of Streptococcus suis

Streptococcus suis is an important agent of swine and human meningitis. Sequence type (ST) 7 emerged in China and was responsible for the human epidemic caused by S. suis in 2005. The virulence of S. suis ST7 is greater than the wild type pathogenic S. suis, ST1; however, the mechanisms for this increased pathogenicity are unknown. The aim of this study was to determine the role of different toll-like receptors (TLRs) involved in regulating the host response to the S. suis infection and to speculate on differing mechanisms used by ST7 strains to induce disease. Here we compared two ST7 strains isolated in the 2005 Sichuan outbreak to two ST1 strains. Our data show TLR2, 6 and 9 are involved in the recognition of heat-killed S. suis independent of the ST type. We found the TLR-dependent cytokine production differed between the two types of strains using whole cell lysate proteins. TLR6 played a greater role in cytokine production induced by the whole cell lysate proteins from the ST7 strain than in that induced by the ST1 strain lysates. The data suggest that mechanisms of inflammation induced by S. suis strains differ where this will be useful in designing efficient strategies in combating streptococcal toxic shock-like syndrome caused by the S. suis ST7 strains.     

猪链球菌病流行病学及其疫苗研究现状

猪链球菌病流行无明显的季节性,一年四季均可发生,尤其是重症猪链球菌2型感染暴发时,致病性强,传播迅速,猪病死率高。该病同时可通过破损皮肤如伤口或擦伤传染给人,也可通过呼吸道感染人,严重感染时可引起人的死亡。控制猪链球菌病的感染,重在预防。不同类型的疫苗已研制成功或正在开发。近年来,基因工程疫苗如重组亚单位疫苗,细菌载体疫苗等新型疫苗的研究具有广泛应用前景。虽然猪链球菌病在猪群中的流行早有报道,但人类感染的报道较少,认识较局限。文章主要对该病的病原特性。流行病学及疫苗的研究做了系统的阐述,为该病的研究提供参考。     

IgA1 protease contributes to the virulence of Streptococcus suis

Streptococcus suis (S. suis) is a major swine pathogen and emerging zoonotic agent. However, the current understanding of the S. suis pathogenesis of infection remains limited. In the present study, the contribution to the pathogenesis of S. suis was evaluated on IgA1 protease (or iga gene), which has been regarded as a virulence factor of gram-negative pathogenic bacteria and of certain gram-positive pathogenic bacteria. In contrast to the wild type (WT) strain of S. suis serotype 2, the isogenic iga mutant (Δiga) constructed by allelic replacement showed significantly decreased lethality to pigs. The present study suggests that IgA1 protease might contribute to S. suis pathogenesis.