Identification and cluster analysis of Streptococcus suis by matrix-assisted laser desorption ionization time-of-flight mass spectrometry / 公共卫生与预防医学

Objective To evaluate the feasibility of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) for identification and cluster analysis of Streptococcus suis. Methods Eighteen clinical isolates biochemically identified as Streptococcus suis were pre-treated by smearing formic acid method and formic acid-acetonitrile extraction method. The identification results and protein profiles of MALDI-TOF-MS method were analyzed and compared. A self-constructed database of profiling with better pretreatment method was established, and cluster analysis was performed on the 18 strains of Streptococcus suis. At the same time, PFGE homology analysis was performed to compare the results of the two genotyping. Results Both pretreatment methods could accurately identify Streptococcus suis with scores above 2.1. The protein fingerprint of formic acid and acetonitrile extraction method had a smoother baseline, fewer miscellaneous peaks and more identifiable ion peaks. Comparison of the results of homology typing showed that the homology results of MALDI-TOF-MS were significantly different from those of PFGE. Conclusion MALDI-TOF-MS can accurately identify Streptococcus suis for the strains pre-treated with formic acid method or formic acid-acetonitrile extraction method, and the formic acid-acetonitrile extraction method can obtain a better protein mapping. MALDI-TOF-MS can play a certain role in typing, but it still has some limitations and cannot completely replace the PFGE.

A case of Streptococcus suis meningitis / 中华神经科杂志

A case of suppurative meningitis caused by Streptococcus suis infection is reported. The patient was an elderly female with an atypical epidemiological history. The common symptoms included fever, headache and cervicodynia. According to the results of blood bacterial culture and next-generation sequencing of cerebrospinal fluid, the patient was considered purulent meningitis caused by Streptococcus suis. After treatment with the third generation cephalosporins, the symptoms improved significantly. One week after the onset of the disease, herpes labialis occurred, followed by hearing loss about 1 week later. The patient was treated with antiviral and hormone therapy, and was discharged after improvement.

Molecular characteristics of Streptococcus suis type 2 from humans in Zhejiang Province / 中华传染病杂志

Objective:To determine the molecular characteristics of Streptococcus suis type 2 (SS2) in Zhejiang Province. Methods:Twenty-nine SS2 sporadic human isolates in Zhejiang Province from Januery 2005 to July 2021 were genotyped by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and minimum core genome (MCG) sequence typing.Results:Among 29 strains, 10 PFGE patterns and three main clusters were obtained by PFGE. Twenty-one (72.41%) of the strains were divided into two main branch groups and the remaining eight (27.59%) showed genetic diversity with the similarity ranging from 49.7% to 94.7%. Three sequence types were obtained from 29 strains by MLST, including ST7 (86.21%(25/29)), ST1 (10.34%(3/29)) and ST25 (3.45%(1/29)). In addition, three genotypes were obtained from 29 strains by MCG, including genotype E (41.38%(12/29)), genotype group 1 (55.17%(16/29)) and genotype group 4 (3.45%(1/29)).Conclusions:Two large clonal groups of highly pathogenic strains of SS2 have been prevalent in Zhejiang Province. A few strains display genetic diversity, indicating genetic variation may exist during transmission.

Biological characteristics and PFGE typing of 12 strains of human Streptococcus suis type 2 in Zhongshan City / 公共卫生与预防医学

Objective To study the biological characteristics of clinical isolates of human infected Streptococcus suis type 2 in Zhongshan City from 2016 to 2019 and classify the strains using pulse-field gel electrophoresis (PFGE), and to provide a scientific basis for clinical prevention and treatment of porcine streptococcus suis disease. Methods Twelve strains of Streptococcus suis type 2 were collected from 2016 to 2019 and identified by automatic bacterial identification instrument. The carrying status of five major virulence genes of Streptococcus suis was detected by nucleic acid and protein analyzer, including capsular polysaccharide (cps2J), lysozyme-releasing protein (mrp), hemolysin (sly), glutamate dehydrogenase (gdh), and extracellular factor (ef). The susceptibility of Streptococcus suis to 12 kinds of commonly used antibiotics was determined by the broth microdilution method, and the homology analysis was carried out by PFGE method. Results Twelve strains of Streptococcus suis type 2 were divided into four virulence genotypes, mainly mrp-/sly+/ef+/cps2J+/gdh+ (6strains) and mrp-/sly-/ef+/cps2J+/gdh+(4strains). Drug susceptibility test results showed that 12 strains of Streptococcus suis type 2 were resistant to erythromycin, tetracycline and clindamycin, and they all were multi-resistant strains. According to the classification results of PFGE, the 12 strains were classified into 7 PFGE types based on 100% similarity coefficient. The PFGE band types of Streptococcus suis in the same year had high homology. Conclusion The virulence genotypes of 12 clinical isolates of human infected type 2 Streptococcus suis in Zhongshan from 2016 to 2019 are diverse, and the strains are resistant to multiple antibiotics. Most strains in the same year are the same clone strains. PFGE genotypes are not correlated with virulence genotypes and drug resistance spectrum.

The value of next-generation sequencing for the diagnosis of Streptococcus suis meningitis

SUMMARY OBJECTIVE: The aim of this study was to investigate the value of next-generation sequencing for the diagnosis of Streptococcus suis meningitis. METHODS: Patients with meningitis in the Department of Neurology of the Hainan General Hospital were recruited and divided into a next-generation sequencing group and a control group. In the next-generation sequencing group, we used the next-generation sequencing method to detect the specific pathogenic bacteria in the patients. In the control group, we used the cerebrospinal fluid bacterial culture method to detect the specific pathogenic bacteria in the patients. RESULTS: A total of 28 participants were recruited for this study, with 14 participants in each group. The results showed similarities in both the average age and average course of the disease between the two groups (p>0.05). The white blood cell count, percentage of neutrophils, and level of C-reactive protein in the next-generation sequencing group were significantly higher than those in the control group (p<0.05). There were similarities in both the temperature and intracranial pressure between the two groups (p>0.05). In the next-generation sequencing group, all patients (100%) were detected as having had the S. suis meningitis infection by next-generation sequencing, while only 6 (43%) patients in the control group had been detected as having the S. suis meningitis infection by cerebrospinal fluid bacterial culture. CONCLUSIONS: The positive detection rate of S. suis by the next-generation sequencing method was significantly higher compared with using a cerebrospinal fluid bacterial culture. Therefore, the next-generation sequencing method is valuable for the diagnosis of S. suis meningitis and is worthy of clinical application.

Antimicrobial resistance in bacteria isolated from pigs with respiratory clinical signs in Brazil / Resistência a antimicrobianos em bactérias isoladas de suínos com sinais clínicos respiratórios no Brasil

Antimicrobial resistance is a current and important issue to public health, and it is usually associated with the indiscriminate use of antimicrobials in animal production. This study aimed to evaluate the antimicrobial susceptibility profile in bacterial isolates from pigs with clinical respiratory signs in Brazil. One hundred sixty bacterial strains isolated from pigs from 51 pig farms in Brazil were studied. In vitro disk-diffusion method was employed using 14 antimicrobial agents: amoxicillin, penicillin, ceftiofur, ciprofloxacin, enrofloxacin, chlortetracycline, doxycycline, oxytetracycline, tetracycline, erythromycin, tilmicosin, florfenicol, lincomycin, and sulfadiazine/trimethoprim. The majority of isolates were resistant to at least one antimicrobial agent (98.75%; 158/160), while 31.25% (50/160) of the strains were multidrug resistant. Streptococcus suis and Bordetella bronchiseptica were the pathogens that showed higher resistance levels. Haemophilus parasuis showed high resistance levels to sulfadiazine/trimethoprim (9/18=50%). We observed that isolates from the midwestern and southern regions exhibited four times greater chance of being multidrug resistant than the isolates from the southeastern region studied. Overall, the results of the present study showed a great level of resistance to lincomycin, erythromycin, sulfadiazine/trimethoprim, and tetracycline among bacterial respiratory pathogens isolated from pigs in Brazil. The high levels of antimicrobial resistance in swine respiratory bacterial pathogens highlight the need for the proper use of antimicrobials in Brazilian pig farms.(AU)

A resistência antimicrobiana é uma questão atual e muito importante para a saúde pública, geralmente associada ao uso indiscriminado de antimicrobianos na produção animal. Diante disso, foi investigado o perfil de sensibilidade-antimicrobiana em isolados bacterianos de suínos com sinais clínicos respiratórios no Brasil. Foram estudadas 96 isolados provenientes de 51 granjas de suínos do Brasil. O método de disco-difusão foi empregado usando 14 antimicrobianos: amoxicilina, penicilina, ceftiofur, ciprofloxacina, enrofloxacina, clortetraciclina, doxiciclina, oxitetraciclina, tetraciclina, eritromicina, tilmicosina, florfenicol, lincomicina e sulfadiazina/trimetoprim. Streptococcus suis e Bordetella bronchiseptica foram os patógenos que apresentaram maiores níveis de resistência. Haemophilus parasuis apresentou altos níveis de resistência à sulfadiazina/trimetoprim (9/18=50%). Observou-se que isolados das regiões Centro-Oeste e Sul apresentaram quatro vezes mais chance de serem multirresistentes do que os isolados da região Sudeste. A maioria foi resistente a pelo menos um agente antimicrobiano (98,75%; 158/160) e 31,25% (50/160) das estirpes isoladas eram multirresistentes. No geral, os resultados do presente estudo mostraram grande nível de resistência à lincomicina, eritromicina, sulfadiazina/trimetoprim e tetraciclina entre patógenos respiratórios bacterianos isolados de suínos no Brasil. Os altos níveis de resistência antimicrobiana em patógenos bacterianos respiratórios em suínos reforçam a necessidade do uso criterioso de antimicrobianos na suinocultura brasileira.(AU)

Epidemiological and pathogenic investigation on the first case of human Streptococcus suis type 2 infection in Minhang District, Shanghai / 公共卫生与预防医学

Objective To investigate and analyze the epidemiological and pathogenic characteristics on a case of human Streptococcus suis type 2 infection in Minhang District, Shanghai, and to provide evidence for early warning and prevention and control measures of rare and imported zoonotic acute infectious diseases in Shanghai. Methods By inquiring the patient medical history and epidemiological history and on-site environmental investigation, the infection route and source of the case were examined. The pathogenic culture of cerebrospinal fluid (CSF) was used to isolate Streptococcus suis, and Vitek2GP was used to identify the isolated strains. The PCR technique was used to detect species specific genes and virulence genes. Results The clinical manifestations of the patient were high fever with headache, nausea, vomiting and stiff neck. Blood tests showed a significant increase in c-reactive protein, an increase in lymphocyte percentage, and a decrease in platelet count. Head CT examination showed bilateral ethmoidal sinus and bilateral maxillary sinus inflammation, and significantly increased CSF white blood cell count and immunoglobulin. The case's CSF sample was positive for species specific genes (16SrRNA) and 2 virulence genes (cps-2j and ef). Conclusion This case was human Streptococcus suis type 2 with meningitis symptoms. Good prognosis was associated with timely diagnosis and treatment as well as the types of virulence factors. Medical institutions should identify early infection and take timely treatment as soon as possible to avoid severe illness and death cases. Departments of agriculture, health, market management, and others should consummate the reporting mechanism of animal epidemic situation, and establish necessary active sentinel monitoring.

Pathogenicity of a Strain of Streptococcus suis Type 2 to Mice and Swine Isolated from Jingzhou City

Aims: The objective of this study is to identify S. suis type 2 and evaluate the virulence of ZHJ01 strain isolation, and verity the clinical and pathological outcome of a systemic infection caused by one serotype 2 when simultaneously inoculated with ZHJ01 strain. We also want to clarify the epidemiologic, clinical, microbiologic characteristics and the pathogenesis mechanism of S. suis type 2 in Hubei province, China. Study Design: Pigs suspected of being infected with S. suis in Jingzhou regions of Hubei province, China were studied. S. suis type 2 isolation was obtained from the suspicion of diseased pig. The case of S. suis type 2 was detected by the virulence factor amplification based on PCR detection and bacterial isolation, identification in the laboratory. According to the experimental infections of mice and piglets, pathogenicity of this S. suis type 2 isolation to mice and swine was monitored. This study was conducted in the key laboratory of pathogenic microbiology, College of Animal Science of Yangtze University, and Institute of Black Pigs Research, Yangtze University. Methodology: Proper serological typing can be performed using a co-agglutination test. The typical colonies purificated and cultured were inoculated with Glucose, Lactose, Raffinos, Sorbitol, D (+)-sucrose, Trehalose, 6.5%NaCl, D (-)-Salicin, Hippurate, Esculin hydrate, V-p, etc., then the test results were recorded. Detection of virulence factors were performed using PCR amplification and DNA sequencing. S.suis type 2 isolation was inoculated to mice and piglets for the virulence test, and the observation of the clinical signs and pathological changes. Results: The virulence factor of extracellular protein factor (EF) was determined from ZHJ01 strain based on PCR detection. Sequence analysis indicated that the isolate was very similar to nucleotide homology with others SS2 strains from different county or contries, and there was not much variation. LD50 of S. suis type 2 for mice was 2.5 x 107cfu. LD50 of S. suis type 2 for piglets was 3.92 x 109cfu. Conclusion: The results show that Swine S. suis type 2 has a relatively strong pathogenicity to pigs in Hubei province, China. This study can be, in part, sufficient to explain the pathogenicity for ZHJ01 strain in area of Zhijing, Jingzhou city, China, which may provide insights into the pathogenesis SS2 and more valid data to support the development of S. suis vaccine as well as the epidemiological investigation, further monitoring and effective prevention to S. suis.

A Case of Life-Threating Streptococcus suis Infection Presented as Septic Shock and Multiple Abscesses

Streptococcus suis is a zoonotic pathogen that can cause severe systemic infections in humans as well as swine. In recent decades, the number of S. suis infections in humans has increased, particularly in Southeast Asia. Although most cases of S. suis human infections are reported as sporadic, a few outbreaks have been noted. Interestingly, these outbreaks have been proposed to be associated with concomitant outbreaks in swine. In Korea, four sporadic and non-fatal cases of S. suis infection have been reported. We herein report a case of life-threating S. suis infection with sepsis for the first time in Korea. The patient was a healthy pig farmer, and the gastrointestinal tract was considered the route of infection. This case emphasized the need for awareness and recognition of S. suis as a zoonotic pathogen.

A Case of Life-Threating Streptococcus suis Infection Presented as Septic Shock and Multiple Abscesses

Streptococcus suis is a zoonotic pathogen that can cause severe systemic infections in humans as well as swine. In recent decades, the number of S. suis infections in humans has increased, particularly in Southeast Asia. Although most cases of S. suis human infections are reported as sporadic, a few outbreaks have been noted. Interestingly, these outbreaks have been proposed to be associated with concomitant outbreaks in swine. In Korea, four sporadic and non-fatal cases of S. suis infection have been reported. We herein report a case of life-threating S. suis infection with sepsis for the first time in Korea. The patient was a healthy pig farmer, and the gastrointestinal tract was considered the route of infection. This case emphasized the need for awareness and recognition of S. suis as a zoonotic pathogen.

Construction and pathogenicity of mutant strain ATP binding cassette transporter SSU05_0948 of Streptococcus suis type 2 / 中华传染病杂志

Objective@#To construct the mutant strain ATP binding cassette transporter SSU05_0948 of Streptococcus suis type 2 and comprehensively study its pathogenicity, and to provide useful insights for understanding the mechanism that Streptococcus suis avoid host innate immunity. @*Methods@#The mutant strain 05ZYH33Δ0948 was constructed through homologous recombination technology. The differences between the mutant strain and the wild type strain were evaluated through bacterial adhesion, whole blood killing, mice meningitis assay, mice and piglets virulence assay. Chi-square test and t test were used. @*Results@#Successfully constructed the mutant strain 05ZYH33Δ0948. The adhesion results showed that the adhesion rate (0.663±0.047)% of the wild strain to A549 cell was significantly higher than that of the mutant (0.246±0.074)%, the difference was statistically significant (χ2=5.267, P=0.014); the adhesion rate (16.540±2.320)% of the wild strain to Hep2 cell was significantly higher than that of the mutant (1.970±0.320)%, the difference was statistically significant (χ2=0.014, P<0.01); the adhesion rate (5.497±0.174)% of the wild strain to Hep2 cell was significantly higher than that of the mutant (1.950±0.335)%, the difference was statistically significant (χ2=0.016, P<0.01). The killing rate (32.970±3.589)% of the wild strain in whole blood is no difference with the mutant (29.560±3.737)% (χ2=1.200, P=0.133). Piglets competitive infection showed that, the competitive index at 12 h, 24 h and 36 h were 0.046±0.003, 0.107±0.003, 0.064±0.001, respectively. 12 h and 24 h was significant differences(t=15.490, P=0.041), 24 h and 36 h was significant differences(t=5.660, P=0.047), 12 h and 36 h was no differences(t=1.445, P=0.285). @*Conclusions@#Streptococcus suis type 2 ABC transporter SSU05_0948 is a new adhesion factor and virulence factor of Streptococcus suistype 2, and also a new meningitis factor, which plays important roles in Streptococcus suis against host innate immunity.

Construction and characterization of the stk and stp1 knockout mutant in streptococcus suis type 2 / 医学研究生学报

Objective Serine /threonine kinases (STK) and phosphatases (STP) regulate various physiological activities of prokaryotes by reversible phosphorylation of proteins .This paper aimed to study the effects of simultaneous deletion of the stk and stp1 genes on the biological characteristics and pathogenicity of streptococcus suis type 2, the Chinese virulent strain 05ZYH33. Methods The double mutant of the stk and stp1 genes of 05ZYH33 was constructed by homologous recombination .The biological characteristics of the wild strain 05ZYH33 and the mutant strain Δstk/stp1 were compared.The effects of the stk and stp1 deletion on bacterial virulence was analyzed using cell adhesion assay , anti-phagocytosis assay and the mouse model of infection . Results RT-PCR showed that the stk and stp1 genes were replaced by the spectinomycin resistance gene Spc r and the mutant strain was successfully constructed .Experi-ments of biological characterization revealed gradually increased value of 05ZYH33 and Δstk/stp1 at 2 hours after inoculation and a plateau period at 7 hours.The logarithmic phase of the mutant strain (A600≈0.4) was 1 hour later than that of the wild one , and the bacterial den-sity of the former was lower than that of the latter after the plateau pe -riod (0.8 vs 1.0).On the blood plates of 05ZYH33 and Δstk/stp1 were observed greyish, round, semitransparent, wet and smooth-sur-faced tiny bacterial colonies , around which there were hemolysis rings with no significant differences in colony morphology and hemolytic ac -tivity.In the experiment on pathogenicity , the mice of the 05ZYH33 group all died within 12 hours while 9 of the 30 mice in the Δstk/stp1 group died within 12 hours and all died within 24 hours. Conclusion The simultaneous deletion of the stk and stp1 genes may mainly affect the regulation of the proteins associated with bacte -rial proliferation and division.

Function of gene 0955 in Streptococcus suis type 2 98HAH33 / 中华微生物学和免疫学杂志

Objective To study the function of gene 0955 in Streptococcus suis type 2 98HAH33. Methods Growth condition of wild-type, mutant and complemented strains of Streptococcus suis type 2 98HAH33 was compared at different stages. Differences in adhesion ability to host cells and anti-phagocyto-sis among these strains were compared by using bacterial adhesion test and analyzing their survival rates in blood. Mouse and piglet models were used to evaluate their virulence. Results The growth of the mutant and the complemented strains was slightly slower than that of the wild type strains in logarithmic growth phase, but no significant difference was found in plateau phase. Bacterial adhesion test showed that gene 0955 might encode a new adhesion factor of Streptococcus suis type 2 98HAH33. Blood bactericidal test sug-gested that gene 0955 was not associated with anti-phygocytosis. Animal experiments showed that gene 0955 might be a novel virulence gene of Streptococcus suis type 2 98HAH33. Conclusion Gene 0955 might en-code a novel adhesion factor and virulence factor of Streptococcus suis type 2 98HAH33.

Mechanism of platelet aggregation induced by Streptococcus suis serotype 2 muramidase-released pro-tein (MRP) / 中华微生物学和免疫学杂志

Objective To study the mechanism of platelet aggregation induced by Streptococcus suis serotype 2 muramidase-released protein (MRP) and to provide scientific proof and theoretical basis for clinical treatment of patients with Streptococcus suis infection. Methods Nickel column affinity chromatogra-phy was used to purify recombinant proteins of MRP-N and MRP-C. Platelet aggregometer, thromboelastog-raphy (TEG) and scanning electron microscope were used to observe the platelet aggregation induced by MRP. Results Streptococcus suis 2 wild type strain,but not the mutant strain ΔMRP,could induce platelet aggregation. It was MRP-N but not MRP-C that induced platelet aggregation. GPRP,an inhibitor of β2inte-grin receptor,could significantly inhibit the platelet aggregation induced by MRP. Conclusion Streptococ-cus suis 2 MRP induces platelet aggregation through β2integrin receptor pathway.

Meningitis e hipoacusia por manipulación de carne porcina / Meningitis and hypoacusia due to swine meat handling

Resumen En Chile se han descrito ocasionalmente casos de meningitis zoonótica por Streptococcus suis ligados a criaderos de cerdos en el sur del país. Presentamos el caso de una mujer que desarrolló un cuadro de meningitis aguda bacteriana por este agente dos días después de manipular un cerdo faenado. No tenía crianza de cerdos ni visitaba granjas de animales. El diagnóstico fue establecido por el cultivo del LCR. Desarrolló una hipoacusia profunda que no mejoró a pesar del uso de corticoesteroides ni tratamiento antimicrobiano, sin otras complicaciones. La meningitis por S. suis es una condición emergente y ligada a porcinos en diferentes formas. La hipoacusia es una complicación frecuente con este agente.

Zoonotic meningitis by Streptococcus suis has been described occasionally in Chile and linked to pig farmers in the south of the country. We report a female case that developed acute bacterial meningitis by this agent, two days after handling a piece of raw swine meat. She did not participate on swine breeding nor visited farms. Diagnosis was obtained by CSF culture. A severe hearing loss and not recovered despite corticosteroids use and antimicrobial treatment, without others complications. Meningitis by S. suis is emerging as a new pathogen and linked to swine in different forms. Hypoacusis happens frequently with this agent.

Purification and enzyme activity assay of filamentous temperature-sensitive protein Z in Streptococcus suis serotype 2 / 中国人兽共患病学报

We conducted purification of filamentous temperature-sensitive protein Z of Streptococcus suis serotype 2 (S.suis 2) and measured its GTPase activity.The ftsz gene in the genome of the Chinese 05ZYH33 strain of S.suis 2 was successfully amplified using PCR,and then the ftsz gene was cloned into prokaryotic expression plasmid pET28a,and the recombinant plasmid pET28a-ftsz was transformed into E.coli BL21.After induction by IPTG,the isolated FtsZ protein was analyzed with SDS-PAGE.Then the recombinant protein was purified by Ni2+-NTA affinity chromatography.The rabbit serum was harvested after immunization with recombinant FtsZ protein,and was analyzed by indirect ELISA and Western blotting.The GTPase activity of FtsZ was measured with the malachite green method.Results showed that successfully constructed recombinant plasmid pET28a-ftsz and the recombinant protein with high purity was obtained;Western blot result indicated that FtsZ could react with the His-tag antibody and the rabbit serum;the polyclonal antibody titer of the rabbit serum reached 1 ∶ 13 107 200;FtsZ have GTPase activity.We successfully prepared S.suis 2 recombinant protein FtsZ having GTPase activity and high titer antiserum would be useful for the further study of S.suis 2 cell division mechanism.

Prokaryotic expression of Rex transcription regulator in Streptococcus suis 2 and in vitro binding assay / 中国人兽共患病学报

We cloned and prokaryoticly expressed the gene encoding Redox regulator(Rex)of Streptococcus suis serotype 2 and analyzed biological information and in vitro binding activity.The encoding Rex gene of SS2-1 strain was amplified by PCR with the designed primers,and then cloned into prokaryotic expression plasmid pET28a.The recombinant plasmid pET28a-Rex was transformed into E.coli BL21.After induced expression by IPTG,the Rex protein was obtained.The binding activity of Rex protein and DNA was analyzed by gel mobility shift assay (EMSA) in vitro.Purification of recombinant protein Rex was successfully expressed.The presence of NAD+ did not have major effect on mobility shift,but addition of NADH almost abolished such a binding activity.By in vitro binding assay,Rex was found to regulate the expression of Prex in response to NADH/NAD+ equilibrium.

Pathogenicity of ABC transporter SSU05 0946 of Streptococcus suis serotype 2 / 中华微生物学和免疫学杂志

Objective To construct a mutant strain of Streptococcus suis type 2 05ZYH33 express-ing ABC transporter SSU05 0946 and to study the pathogenicity of ABC transporter SSU05 0946 for better understanding the immune evasion strategies by Streptococcus suis. Methods Genome of the Streptococcus suis type 2 05ZYH33 strain was extracted and used as a template to amplify SSU05 0946 upstream and down-stream homeodomains. Chloramphenicol-resistance gene was amplified by using pSET1 plasmid as the tem-plate. These three amplified fragments were fused and integrated with the thermo-sensitive plasmid pSET4s by using overlap extension PCR. Homologous recombination method was used to construct the mutant strain 05ZYH33Δ0946. Differences between the mutant and wild type strains were evaluated through bacterial ad-hesion assay,whole blood killing assay and challenge test in mice and piglets. Results The mutant strain 05ZYH33Δ0946 was successfully constructed. Results of bacterial adhesion assay demonstrated that SSU05 0946 was not involved in the adherence of Streptococcus suis to human epithelial cells. SSU05 0946 was an ovel anti-phagocytic factor and virulence factor of Streptococcus suis. Conclusion Streptococcus suis type 2 ABC transporter SSU05 0946 is a newly discovered virulence factor of Streptococcus suis, playing an impor-tant role in the evasion of host innate immunity by Streptococcus suis.

A serine/threonine phosphatase 1 of Streptococcus suis type 2 is an important virulence factor

Streptococcus suis is regarded as one of the major pathogens of pigs, and Streptococcus suis type 2 (SS2) is considered a zoonotic bacterium based on its ability to cause meningitis and streptococcal toxic shock-like syndrome in humans. Many bacterial species contain genes encoding serine/threonine protein phosphatases (STPs) responsible for dephosphorylation of their substrates in a single reaction step. This study investigated the role of stp1 in the pathogenesis of SS2. An isogenic stp1 mutant (Δstp1) was constructed from SS2 strain ZJ081101. The Δstp1 mutant exhibited a significant increase in adhesion to HEp-2 and bEnd.3 cells as well as increased survival in RAW264.7 cells, as compared to the parent strain. Increased survival in macrophage cells might be related to resistance to reactive oxygen species since the Δstp1 mutant was more resistant than its parent strain to paraquat-induced oxidative stress. However, compared to parent strain virulence, deletion of stp1 significantly attenuated virulence of SS2 in mice, as shown by the nearly double lethal dose 50 value and the lower bacterial load in organs and blood in the murine model. We conclude that Stp1 has an essential role in SS2 virulence.

Characterization of Streptococcus suis through serotyping, SE-AFLP and virulence profile / Caracterização de Streptococcus suis por sorotipagem, SE-AFLP e perfil de virulência

Streptococcus suis is one of most important pathogens in the swine industry worldwide. Despite its importance, studies of S. suis characterization in South America are still rare. This study evaluates S. suis isolates from distinct Brazilian states, from 1999 to 2004, and its molecular and serological characterization. A total of 174 isolates were studied. S. suis identification was confirmed by PCR and isolates were further serotyped and genotyped by SE-AFLP and amplification of virulence markers. Serotype 1, 2, 3, 4, 7, 18, 22 and 32 were identified among the studied isolates, and only 4% were characterized as non-typeable. The mrp+/epf+/sly+ genotype was the most frequent. The SE-AFLP analysis resulted in 29 patterns distributed in three main clusters with over 65% of genetic similarity. Isolates presented a slight tendency to cluster according to serotype and origin; however, no further correlation with virulence genotypes was observed.(AU)

Streptococcus suis é um dos patógenos de maior importância para indústria suinícola mundial. Apesar de sua importância, a caracterização de isolados de S. suis na América do Sul ainda é pouco descrita. O presente estudo descreve a avaliação de isolados de S. suis provenientes de diferentes Estados brasileiros, e sua caracterização sorológica e molecular. Foram avaliados 174 isolados de S. suis e os mesmos foram submetidos a SE-AFLP e pesquisa de marcadores de virulência. Os sorotipos 1, 2, 3, 4, 7, 18, 22 e 32 foram identificados dentre os isolados estudados e apenas 4% foram caracterizados como não tipáveis. O perfil de virulência mrp+/epf+/sly+ foi o mais frequente. A análise do SE-AFLP resultou em 29 perfis distribuídos em três grupos principais com mais de 65% de similaridade genética. Os isolados apresentaram tendência de se agrupar segundo origem e sorotipo; no entanto, não foi observada correlação entre os grupamentos e os perfis de virulência.(AU)