Role of Capsule and Suilysin in Mucosal Infection of Complement-Deficient Mice with Streptococcus suis

Virulent Streptococcus suis serotype 2 strains are invasive extracellular bacteria causing septicemia and meningitis in piglets and humans. One objective of this study was to elucidate the function of complement in innate immune defense against S. suis. Experimental infection of wild-type (WT) and C3^−/− mice demonstrated for the first time that the complement system protects naive mice against invasive mucosal S. suis infection. S. suis WT but not an unencapsulated mutant caused mortality associated with meningitis and other pathologies in C3^−/− mice. The capsule contributed also substantially to colonization of the upper respiratory tract. Experimental infection of C3^−/− mice with a suilysin mutant indicated that suilysin expression facilitated an early disease onset and the pathogenesis of meningitis. Flow cytometric analysis revealed C3 antigen deposition on the surface of ca. 40% of S. suis WT bacteria after opsonization with naive WT mouse serum, although to a significantly lower intensity than on the unencapsulated mutant. Ex vivo multiplication in murine WT and C3^−/− blood depended on capsule but not suilysin expression. Interestingly, S. suis invasion of inner organs was also detectable in C5aR^−/− mice, suggesting that chemotaxis and activation of immune cells via the anaphylatoxin receptor C5aR is, in addition to opsonization, a further important function of the complement system in defense against mucosal S. suis infection. In conclusion, we unequivocally demonstrate here the importance of complement against mucosal S. suis serotype 2 infection and that the capsule of this pathogen is also involved in escape from complement-independent immunity.     

广州地区肺炎住院患儿感染肺炎链球菌的血清型分布及耐药性研究

目的了解广州地区肺炎住院的患儿感染肺炎链球菌的耐药性及血清型分布情况。方法用吸痰法采集患儿痰标本进行涂片，革兰氏染色镜检，合格痰标本划线接种血平板，用E-test法检测分离到的肺炎链球菌对青霉素、阿莫西林、头孢曲松、头孢呋辛、亚胺培南、氧氟沙星、万古霉素、红霉素和克林霉素9种药物的耐药性，采用K-B法检测四环素、复方新诺明的耐药性，并采用荚膜肿胀技术对分离到的79株肺炎链球菌进行血清分型。结果79株肺炎链球菌中青霉素耐药肺炎链球菌（PRSP）11．4％，青霉素中介肺炎链球菌（PISP）77．2％，青霉素敏感肺炎链球菌（PSSP）11．4％，对红霉素、克林霉素的耐药率分别为100％和93．7％，对阿莫西林、氧氟沙星、万古霉素的耐药率均为0，对头孢曲松、头孢呋辛、亚胺培南的耐药率分别为3．8％、72．2％、2．5％。79株肺炎链球菌中只有1株PSSP仅对红霉素耐药．78株肺炎链球菌对两种以上药物耐药．多重耐药率为98．7％（78／79），同时对克林霉素、红霉素、四环素、复方新诺明耐药的菌株65株，占82．3％（65／79）。79株肺炎链球菌血清型分别为19F（70．9％），23F（16．5％），6B（5．1％），4（2．5％），15B（2．5％），不能分型（2．5％），7价疫苗涵盖率为94．9％（75／79）。结论广州地区肺炎住院患儿肺炎链球菌对大环内脂类抗生素红霉素和林可酰胺类抗生素克林霉素耐药情况严重，对二代头孢菌素头孢呋辛耐药率居高，临床治疗儿童肺炎链球菌感染的肺炎应首选阿莫西林和三代头孢菌素。7价疫苗覆盖率高。预防儿童肺炎链球菌感染所致的肺炎，采用7价疫苗可以达到很好效果。     

Molecular Basis of Resistance to Selected Antimicrobial Agents in the Emerging Zoonotic Pathogen Streptococcus suis

Characterization of 227 Streptococcus suis strains isolated from pigs during 2010 to 2013 showed high levels of resistance to clindamycin (95.6%), tilmicosin (94.7%), tylosin (93.8%), oxytetracycline (89.4%), chlortetracycline (86.8%), tiamulin (72.7%), neomycin (70.0%), enrofloxacin (56.4%), penicillin (56.4%), ceftiofur (55.9%), and gentamicin (55.1%). Resistance to tetracyclines, macrolides, aminoglycosides, and fluoroquinolone was attributed to the tet gene, erm(B), erm(C), mph(C), and mef(A) and/or mef(E) genes, aph(3′)-IIIa and aac(6′)-Ie-aph(2″)-Ia genes, and single point mutations in the quinolone resistance-determining region of ParC and GyrA, respectively.     

Identification and characterisation of hyaluronate lyase from Streptococcus suis

Hyaluronate lyase, which catalyses the degradation of hyaluronic acid (HA), has been described from several pathogenic streptococcal species. We describe, for the first time, identification and purification of hyaluronate lyase from the zoonotic pig pathogen Streptococcus suis. We have cloned the hyaluronate lyase gene from S. suis and used it to generate an allelic replacement knock-out mutant of S. suis serotype 7 that can no longer biosynthesise the enzyme. Interestingly, a limited strain survey indicates that hyaluronate lyase activity is not present in all disease isolates of S. suis. Polyclonal anti-hyaluronate lyase anti-serum raised against our recombinant hyaluronate lyase has been used in Western blots, showing that hyaluronate lyase activity is always associated with the presence of protein of the expected size, whereas lack of hyaluronate lyase activity is due to truncation or absence of the enzyme. We show that hyaluronate lyase activity is required for S. suis to use HA polymer as a carbon source and that supplying exogenous recombinant hyaluronate lyase to all S. suis strains tested allowed fermentation of the resultant HA breakdown products.     

Distribution of environmentally regulated genes of Streptococcus suis serotype 2 among S. suis serotypes and other organisms

The occurrence of 36 environmentally regulated genes of Streptococcus suis strain 10 among all 35 S. suis serotypes was determined by using hybridization with the amplified genes as probes. In addition, the distribution of these genes among the virulence phenotypes of serotypes 1 and 2 was assessed. Hybridization was also performed with various other streptococcal species and nonstreptococcal bacterial species which may be present in pigs. Interestingly, probe ivs-25/iri-1, similar to agrA and sapR, hybridized only with S. suis serotype 1 and 2 strains with virulent phenotypes and is therefore suitable as a diagnostic parameter. Only one probe was specific for S. suis. This probe's sequence was identical to the epf gene, a putative virulence factor of S. suis. Probe ivs-31 was similar to a virulence factor of S. suis, namely, a gene encoding a fibronectin- and fibrinogen-binding protein. This probe hybridized only with oral streptococci. Nearly half of the probes (45%) hybridized with the oral streptococci (S. oralis, S. milleri, S. sanguis, S. gordonii, and S. mitis) and with Streptococcus pneumoniae. This indicates a close relationship between S. suis, the oral streptococci, and S. pneumoniae with respect to the selected environmentally regulated genes. One probe only hybridized with gram-negative species and therefore seems to be obtained by S. suis from a gram-negative organism by horizontal transfer.     

Genetic diversity of Streptococcus suis strains isolated from pigs and humans as revealed by pulsed-field gel electrophoresis

The genetic diversity of 123 Streptococcus suis strains of capsular types 2, 1/2, 3, 7, and 9, isolated from pigs in France and from humans in different countries, was evaluated by pulsed-field gel electrophoresis (PFGE) of DNA restricted with SmaI. The method was highly discriminative (D = 0.98), results were reproducible, and the PFGE analysis was easy to interpret. Among all S. suis strains, 74 PFGE patterns were shown. At 60% homology, three groups (A, B, and C) were identified, and at 69% homology, eight subgroups (a to h) were observed. Strains isolated from diseased pigs or from humans were statistically clustered in group B, especially in subgroup d. By contrast, S. suis strains isolated from clinically healthy pigs were preferentially included in subgroup b of group A. Relationships could be established between capsular types 1/2, 3, and 9 and groups A, e, and B, respectively. S. suis strains isolated from humans were homogeneous, and a very high level of association between these strains and four DNA patterns was observed. The PFGE used in this study is a very useful tool for evaluating the genetic diversity of S. suis strains, and it would be used for epidemiological investigations.     

Characterization of prototype and clinically defined strains of Streptococcus suis by genomic fingerprinting.

A collection of Streptococcus suis strains from animal and human infections was examined for DNA-banding patterns after restriction endonuclease digestion and agarose gel electrophoresis. The endonuclease HaeIII produced the most discriminating restriction profiles among 23 serotypes studied. DNA from serotypes 9, 11, 12, and 16 was resistant to HaeIII cleavage. DNA from serotypes 9 through 16 was cleaved with HindIII and showed substantial genomic differences. We also examined 106 epidemiologically unrelated strains isolated from cases of pig meningitis or pneumonia and 5 strains isolated from cases of human meningitis in order to compare genomic fingerprinting and serotyping as epidemiological tools. Heterogeneity was found among fingerprints of serologically identical isolates, indicating genetic diversity within some serotypes. DNA fingerprints of some serotype 2 strains from different sources appeared identical, suggesting a clonal relationship among strains of this serotype. The data suggest that this technique represents an important tool for examining the natural history of disease caused by S. suis.     

Molecular Characterization and Prophage DNA Contents of Streptococcus agalactiae Strains Isolated from Adult Skin and Osteoarticular Infections

Skin and osteoarticular infections (SKI and OAI, respectively) account for almost one-third of Streptococcus agalactiae infections in nonpregnant adults. We evaluated the genetic diversity and phylogeny of 58 S. agalactiae strains responsible for adult SKI or OAI and of 61 S. agalactiae strains from cases of adult human colonization (HCol) by serotyping and multilocus sequence typing (MLST). We also assessed the prophage DNA content of the genomes of these strains by a PCR-based method. We found that 63% of SKI and 56% of OAI occurred in people aged 55 years and over. Overall, 71% of SKI strains were of serotype Ia or V, and 91% of OAI strains were of serotype Ia, III, or V. Strains of clonal complexes 1 and 23 (CC1 and CC23) were associated with 79% of SKI cases and 62% of OAI cases. Seven groups of strains, groups A, B, C, D, E, F, and G, were obtained by performing a hierarchical analysis on the basis of prophage DNA-PCR data. We found that 85% of CC1 strains clustered in DNA prophage group D, the group with the highest prophage DNA content (average, 4.4; average of absolute deviations [AVEDEV], 0.9). The CC23 strains displayed the greatest diversity in prophage DNA fragment content, but 47% of CC23 strains clustered in group B, which also had a high average prophage DNA content per strain (average, 2.3; AVEDEV, 0.6). Many (65%) of the OAI strains were in prophage DNA group D, whereas 83% of the SKI strains were in prophage DNA groups B and D. These data suggest that S. agalactiae strains from CC1 and CC23 may be subject to particular transduction mechanisms in gene recombination, rendering them particularly capable of invading the skin, bone, or joints in adults.Streptococcus agalactiae was initially described in 1887 as an animal pathogen causing bovine mastitis (36). Since the 1960s, when human vaginal carriage of S. agalactiae was first documented, S. agalactiae has frequently been linked to neonatal infections and this bacterium has become the leading neonatal pathogen in developed countries (10, 13, 22, 23, 27, 34). S. agalactiae was rarely isolated from nonpregnant adults until 2 decades ago, when such infections began to be reported, particularly for the elderly and for individuals with underlying conditions such as diabetes mellitus, cancer, and a compromised immune system (4, 15, 37, 40-42). However, such infections have been reported even for adults without a known susceptibility factor (29, 33). Many case reports of clinical skin and osteoarticular infections (SKI and OAI, respectively) due to S. agalactiae in adults have been published in recent years, with these infections accounting for at least one-third of the reported cases of S. agalactiae infection in adults (41, 42).Many genetic markers have been identified as associated with S. agalactiae clones specifically responsible for meningitis in neonates. Indeed, most of the S. agalactiae strains isolated from the cerebrospinal fluid of neonates belong to clonal complex 17 (CC17) and have particular mobile genetic elements, such as the group II intron GBSi1 (2) and particular prophage DNA fragments (47). No particular markers or virulence factors of S. agalactiae strains have been associated with any other disease.Phages are important vehicles for horizontal gene exchange within bacterial populations and account for much of the genomic variation observed within bacterial species (8, 11, 28). Temperate phages affect bacterial fitness by modifying anchor points for genomic rearrangements, by disrupting genes, by protecting against lytic infection, by lysing competing strains through prophage induction, and by introducing new fitness factors (8, 19). Prophage acquisition, accounting for much of the molecular diversity of the Streptococcus pyogenes genome, rendered some of the strains of this species virulent through the acquisition of phage-encoded virulence factors and enhanced pathogen survival by improving resistance to host defenses under certain circumstances (1, 9). Little is currently known about S. agalactiae phages. They were first isolated in 1969 (39), and more-recent analyses of sequenced S. agalactiae strains have revealed the presence of abundant regions resembling prophages (16, 44, 45). We recently induced phages from S. agalactiae strains of various phylogenetic lineages, characterized them molecularly, and determined their lytic activities (12). The various molecular phage groups were found to correspond to particular strain lineages, with specific morphological features and lytic activities, suggesting a role for phage-mediated horizontal gene transfer in the evolution of the species and the emergence of lineages with a more specific role in particular diseases.In this study, we characterized S. agalactiae strains isolated from skin and osteoarticular infections in adults, using serotyping and multilocus sequence typing (MLST) to determine the phylogenetic relationships and molecular features of the strains involved through comparison with the characteristics of strains involved in human colonization (HCol). We used a PCR-based method recognizing S. agalactiae prophages to determine the prophage content of strain genomes (12). The genetic relationships between prophage DNA regions of strains were determined by hierarchical analysis. Correlations between the prophage DNA content, the clinical circumstances of isolation, and the phylogenetic position of S. agalactiae strains were investigated.     

Genetic Characterization of Four Strains Borrelia Burgdorferi Isolated in China

TheetiologicalagentofLymediseaseisBorreliaburgdor feri,whosegenomicgroupshaveimportantmeaninginepi demiology,clinicdiagnosis,treatmentandvaccinedevel opment[1].Sofarallisolatedstrainshavebeendivided intotendifferentgenotypesintheworld,including:B. burgdorferisensustricto(B.b.ss),Borreliagarinii (B.g),Borreliaafzelii(B.a),Borreliajaponica, Borreliavalaisiana,Borreliaandersonii,Borreliaturdi, Borreliatanukii,Borrelialusitaniae,andBorreliabisset tii(namedDN127groupinthepast)[2].Someofth…     

Response of Freshly Isolated Strains of Streptococcus mutans and Streptococcus mitior to Change in pH in the Presence and Absence of Fluoride During Growth in Continuous Culture

A study was undertaken to compare the effects of pH and fluoride on the growth and metabolic properties of Streptococcus mutans 2452 and Streptococcus mitior 572, strains recently isolated from 8-year-old school children and grown in continuous culture with a glucose limitation. Each experiment had four consecutive stages of growth: (i) pH 7.0, (ii) no pH control, (iii) pH 7.0, and (iv) no pH control plus 50 μg of fluoride per ml in the medium. At a dilution rate (D) of 0.13 h ⁻¹, cells of S. mitior possessed high glycolytic activity at pH 7.0 in the initial stage, but were washing out of the chemostat within 24 h after the pH control was shut off and the pH fell to 5.1. Once the culture was reestablished at pH 7.0, fluoride (50 μg/ml) was added to the medium and the pH control was again turned off. Whereas cell numbers fell from 24.0 × 10⁸ to 0.9 × 10⁸/ml within 24 h, the culture remained relatively constant during the following 6 days despite the fall in pH to 5.4. The cells from this culture also maintained an intermediate glycolytic rate of 0.44 μmol mg⁻¹ min⁻¹. The cells in this latter stage developed phenotypic resistant to fluoride at concentrations up to 16 mM. Growth of S. mitior at D = 0.034 h⁻¹ resulted in a slower response to environmental change such that cells were able to grow to pH values as low as 5.2 in the absence of fluoride. In contrast to S. mitior, S. mutans 2452 under the same conditions at D = 0.13 h⁻¹ grew to higher cell numbers and higher yields and was able to maintain significant cell numbers to pH 4.8 once the pH control was shut off in the presence and absence of fluoride. S. mutans had 40% less glycolytic activity but was fourfold more resistant to fluoride at the start of the experiment, and cells were shown to adapt to growth at low pH and to fluoride at levels as high as 20 mM. This fluoride resistance by freshly isolated S. mutans 2452 was significantly higher than that of S. mutans DR0001 grown under identical conditions in the chemostat. S. mutans DR0001 is a strain which has been subcultured in vitro for several years. This study demonstrated that S. mutans 2452 was more aciduric than S. mitior 572 and, unlike the latter organism, could grow at pH values below 5.1. The addition of fluoride to the medium stabilized the S. mitior culture in the absence of pH control, indicating that whereas fluoride does suppress growth and glycolytic activity it also results in higher environmental pH values, which permit the survival of the less aciduric bacteria.     

中国尖音库蚊复合组蚊虫的抗性动态和遗传多样性研究

本文通过采用生物测定、蛋白质电泳和等位酶分析等方法对4个地理种群尖音库蚊复合组蚊虫(Culex pipiens comples)的抗性水平、群体中酯酶基因表型分布和种群遗传多样性进行了研究.抗性检测结果表明,4个库蚊种群对敌敌畏、对硫磷、氯菊酯和溴氰菊酯的抗性较高,对残杀威、巴沙和胺菊酯的抗性较低.4个种群抗性大小是:山东淄川>湖北沙市>广东茂名>北京沙河,淄川种群蚊虫对敌敌畏抗性为66.7倍.酯酶电泳结果中,沙市和茂名2个库蚊种群酯酶表型多态性最高,淄川库蚊种群多态性最低,过量表达的B1比率占100%.种群遗传多样性研究表明,每位点平均等位基因数(A)为1.92,平均多态位点百分率(P)为52.78%,平均预期杂合度(He)为0.130,群体间遗传分化系数(Fst)值为0.368,平均基因流Nm=1.52,说明4个种群有较丰富的遗传多样性,群体之间存在相当多的遗传多样性,种群间的基因交流较低,遗传分化较大,表明与地理位置存在一定对应关系.     

Diversity of Staphylococcus aureus Strains Isolated from Two European Regions with Different Prevalences of Methicillin Resistance

The genodiversity of Staphylococcus aureus isolates from the Nottingham region of the United Kingdom was compared with isolates from the Freiburg region of Germany. The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) isolates was higher in Nottingham than in Freiburg. In patients from Nottingham hospitals, 80% of MRSA isolates were classical epidemic MRSA-15, but genotypic variants of epidemic MRSA-15 comprised 72% of isolates from Nottingham community-based patients. In contrast, MRSA isolates from Freiburg showed greater diversity, but 47% and 23% of isolates, respectively, belonged to two predominant MRSA genotypes found in isolates from both hospitalised and community-based patients. The results suggest that genodiversity becomes increasingly more confined in settings with a higher frequency and longer duration of MRSA prevalence. Electronic Publication     

Immunomagnetic Isolation of Streptococcus suis Serotypes 2 and 1/2 from Swine Tonsils

Isolation of specific serotypes of Streptococcus suis from the tonsils, nasal cavities, and genital tract is difficult, since low-pathogenic serotypes and untypeable strains also inhabit these sites. An immunomagnetic separation (IMS) technique for the selective isolation of S. suis serotypes 2 and 1/2 was standardized. Superparamagnetic polystyrene beads (immunomagnetic beads or IMB) were coated with either a purified monoclonal antibody (MAb) directed to a capsular sialic acid-containing epitope or purified rabbit immunoglobulin G (polyclonal antibody [PAb]), both specific for S. suis serotypes 2 and 1/2. The amount of antibodies required for optimum coating of the beads, the number of IMB required for optimum bacterial recovery, and the nonspecific carryover were considerably higher with the MAb-IMS technique than with the PAb-IMS technique. The sensitivity of the IMS technique was 10(1) CFU/0.1 g of tonsil. The presence of serotype 1/2 bacteria did not considerably affect the recovery rate of a serotype 2 strain and vice versa. To validate the technique, PAb-coated beads were used to study 192 tonsils from animals from S. suis serotype 2- or 1/2-infected herds. Results showed that significantly more positive tonsils were detected by the IMS technique than by the standard procedure. This method represents an innovative and highly sensitive approach for the isolation of S. suis serotypes 2 and 1/2 from carrier animals.     

In Vitro Characterization of the Microglial Inflammatory Response to Streptococcus suis,an Important Emerging Zoonotic Agent of Meningitis

Streptococcus suis is an important swine and human pathogen responsible for septicemia and meningitis. In vivo research in mice suggested that in the brain, microglia might be involved in activating the inflammatory response against S. suis. The aim of this study was to better understand the interactions between S. suis and microglia. Murine microglial cells were infected with a virulent wild-type strain of S. suis. Two isogenic mutants deficient at either capsular polysaccharide (CPS) or hemolysin production were also included. CPS contributed to S. suis resistance to phagocytosis and regulated the inflammatory response by hiding proinflammatory components from the bacterial cell wall, while the absence of hemolysin, a potential cytotoxic factor, did not have a major impact on S. suis interactions with microglia. Wild-type S. suis induced enhanced expression of Toll-like receptor 2 by microglial cells, as well as phophotyrosine, protein kinase C, and different mitogen-activated protein kinase signaling events. However, cells infected with the CPS-deficient mutant showed overall stronger and more sustained phosphorylation profiles. CPS also modulated inducible nitric oxide synthase expression and further nitric oxide production from S. suis-infected microglia. Finally, S. suis-induced NF-κB translocation was faster for cells stimulated with the CPS-deficient mutant, suggesting that bacterial cell wall components are potent inducers of NF-κB. These results contribute to increase the knowledge of mechanisms underlying S. suis inflammation in the brain and will be useful in designing more efficient anti-inflammatory strategies for meningitis.Streptococcus suis is one of the most important swine pathogens worldwide, as well as an important agent of zoonosis. So far, 35 serotypes have been described, although serotype 2 is still the most frequently isolated from both swine and humans. In swine, meningitis is the most striking feature of the infection, although other pathologies, such as septicemia, endocarditis, pneumonia, and arthritis, have been described (35). Although the most common pathology associated with S. suis infection in humans is also meningitis, cases of septicemia with septic shock, endocarditis, and several other clinical manifestations have been reported (69, 71). As a zoonosis, S. suis infection has been traditionally considered an occupational hazard, since most cases described in Western countries have occurred in people working in close contact with pigs or raw pork products. The situation in Asian countries is completely different, as the common population is affected. In addition to an important human outbreak in China caused by S. suis in 2005 (71), the pathogen has recently been reported to be the most frequent cause of bacterial meningitis in adults in Vietnam (29) and the third most common culture-confirmed cause of community-acquired bacterial meningitis in Hong Kong. People who survive S. suis infection may be handicapped, as severe postinfection sequels, such as deafness, may develop (67, 68).In recent years, a number of important studies describing the proposed virulence factors of S. suis serotype 2 have been published (4, 29). However, few candidates have been shown to be critical for virulence. Among them, the capsular polysaccharide (CPS) is considered an important antiphagocytic factor (13). Although not essential for virulence, a hemolysin (suilysin) produced by most virulent strains in Eurasia has also been shown to be toxic for cells of murine, human, and swine origin (12, 14, 55, 66).The pathogenesis of S. suis infection has been partially elucidated. In swine, infection occurs through the respiratory route with subsequent colonization of the tonsils, while in humans, access is mainly through skin cuts and/or the oral route (3, 28, 29). Once S. suis reaches the bloodstream, it travels either free or associated with monocytes (27), with invasion of different tissues and organs. The high mortality observed at this stage of the disease may be associated with septic shock with an exacerbated release of proinflammatory cytokines (18, 19). However, if the host overcomes septicemia, S. suis may still invade the central nervous system (CNS) and cause meningitis and, in some cases, encephalitis. The mechanisms used by the pathogen to gain access to the brain and induce local inflammation are still under debate. It is likely that access is by transcytosis and/or toxicity to brain microvascular endothelial cells (66) and/or choroid plexus epithelial cells that are part of the blood brain barrier (BBB) (64). Increase of BBB permeability due to inflammation cannot be ruled out (27).Recently, our laboratory developed an in vivo mouse model of meningitis/encephalitis after S. suis infection via the intraperitoneal route (18). Using this model, an important inflammatory response in the CNS with expression of different proinflammatory genes, including Toll-like receptor 2 (TLR2), CD14, IκBα (an index of NF-κB expression), interleukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α), and monocyte chemoattractant protein 1 (MCP-1), was observed. Interestingly, the expression of these genes and bacterial antigens was found to probably be associated with microglia and, to a lesser extent, with astrocytes (18). Microglia, the macrophage-like population within the CNS, represent the first line of defense against invading pathogens and have proinflammatory effector functions (49). Although previous findings draw attention to the implication of these cells in the development of meningitis and encephalitis, it is critical to dissect how the cells initiate key proinflammatory mechanisms in order to respond to S. suis infection. Hence, the goal of this study was to explore the murine microglial response to a virulent strain of S. suis, as well as isogenic mutants defective in either CPS or suilysin production. The ability of microglia to internalize S. suis, to activate TLRs, and to secrete different proinflammatory mediators, as well as to activate important inflammatory intracellular signaling pathways, was evaluated.     

Characterization of Five Zoonotic Streptococcus suis Strains from Germany,Including One Isolate from a Recent Fatal Case of Streptococcal Toxic Shock-Like Syndrome in a Hunter

A Streptococcus suis isolate from a German hunter with streptococcal toxic shock-like syndrome (STSLS) and four additional zoonotic isolates were genotyped as mrp⁺epf* (variant 1890) sly⁺cps2⁺. All five zoonotic German strains were characterized by high multiplication in human blood samples ex vivo, but induction of only low levels of proinflammatory cytokines compared to a Chinese STSLS strain.     

广州地区老年人肺炎链球菌临床分离株的青霉素耐药研究与分子分型

目的调查广州地区老年患者肺炎链球菌分离株对青霉素的敏感性，并分析其亲缘关系。方法K—B纸片法对33株分离自老年住院病人的肺炎链球菌进行青霉素药敏试验；应用PCR技术检测青霉素结合蛋白基因pbp1a，pbp2x，pbp2b；用盒式PCR（BOX—PCR）分析菌株间亲缘关系。用多位点测序分型技术（multilocus sequence typing，MLST）检测青霉素耐药菌株的分子分型。结果青霉素的耐药率为3．03％（1／33）：用PCR方法鉴定PSSP的准确率为68．75％；BOX-PCR可将这33株肺炎链球菌分为21型。MIST分型显示，青霉素耐药菌株属ST271型。结论广州地区老年患者肺炎链球菌对青霉素耐药率较低．用PCR方法检测PSSP有一定的可行性。BOX—PCR显示了较高的分辨率，能快速可靠地检测菌株间的亲缘关系。广州地区流行的耐药克隆与Taiwan^19F-14株同源。