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Effect of Spatial Separation of Pigs on Spread of Streptococcus suis Serotype 9  [PDF]
Niels Dekker, Annemarie Bouma, Ineke Daemen, Don Klinkenberg, Leo van Leengoed, Jaap A. Wagenaar, Arjan Stegeman
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0061339
Abstract: The spread of an infectious agent in a population can be reduced by interfering in the infectiousness or susceptibility of individuals, and/or in their contact structure. The aim of this study was to quantify the effect of prevention of direct contact between infectious and susceptible pigs on the transmission of Streptococcus suis (S. suis). In three replicate experiments, S. suis-free pigs were housed in boxes either in pairs (25 pairs) or alone (15 pigs). The distance between the boxes was ±1 m. At 7 weeks of age, one pig of each pair was inoculated intranasally with S. suis serotype 9; the other pigs were exposed to S. suis by either direct (pairs) or indirect contact (individually housed pigs). Tonsillar brush and saliva swab samples from all pigs were collected regularly for 4 weeks post inoculation to monitor colonization with S. suis. All inoculated pigs became infected, and their pen mates became colonized within 2 days. Thirteen indirectly exposed pigs became positive within 7–25 days after exposure. The rate of direct transmission βdir was estimated to be 3.58 per pig per day (95% CI: 2.29–5.60). The rate of indirect transmission increased in time, depending on the cumulative number of days pigs tested positive for the presence of S. suis. The estimate β’ind was 0.001 (95% CI: 0.0006–0.0017) new infections per pig per day for each day that an infected pig was tested positive for S. suis. We conclude that prevention of direct contact reduces the rate at which susceptible pigs become colonized. Simulation studies using these parameters showed, however, that such intervention measure would not limit S. suis serotype 9 spread in a commercial pig farm to a relevant extent, implying that spatial separation of groups op pigs within a compartment would not be effective on a farm.
Immunoprotection from Streptococcus suis serotype 2 suilysin and its antiserum  [cached]
Li-na LIU,Jun-min ZHU,Yan-guang CONG,Chang-jun WANG
Medical Journal of Chinese People's Liberation Army , 2011,
Abstract: Objective To investigate the immunoprotection of Streptococcus suis serotype 2(SS2) suilysin(SLY) and its antiserum.Methods Mice were immunized with the purified SLY recombinant protein.The antiserum against SLY was collected and used to determine the specific antibody titers and IgG isotypes.Subsequently,the active immunized mice were challenged with a lethal dose of S.suis 2.Moreover,the immunoprotection of SLY was evaluated.The antiserum against SLY was used passively to immunize the mice,which were challenged with a lethal dose of S.suis 2 after four hours.The protection provided by the antiserum against S.suis 2 was evaluated.Results The antiserum for mice immunized with recombinant protein SLY was collected.The titer reached 1∶25600,containing IgG1and IgG2a,two kinds of subtype antibodies.However,the difference between IgG1 and IgG2a was not significant.All actively immunized mice were injected with a lethal dose of S.suis 2.The survival rate of the actively immunized mice was significantly higher(60%) than that of the control group(10%)(P < 0.05).Mice that are passively immunized with SLY antiserum were challenged with a lethal dose of S.suis 2.On the 7th day after challenge,the survival rate was significantly higher(90%) than that in the control group(20%)(P < 0.05).Significant differences in survival rates were not observed between the passively immunized and the control group(P > 0.05) 14 days after the challenge.Conclusions SLY and SLY-specific antiserum provides immunoprotection.
Experimental Infection of Conventional Pigs with Streptococcus suis serotype 2 by Aerosolic Exposure
LW Madsen, B Nielsen, B Aalb?k, HE Jensen, JP Nielsen, HJ Riising
Acta Veterinaria Scandinavica , 2001, DOI: 10.1186/1751-0147-42-303
Abstract: In order to evaluate the pathogenesis of S. suis type 2 infection in pigs, we aimed at establishing an aerosol model for the infection using unanaesthetized conventionally reared, weaned pigs. The present report describes the microbiological and pathological findings in a pilot study of an aerosol model for S. suis infection in conventional pigs.Four clinically healthy, 6-week-old, female, Landrace-Yorkshire crossbred pigs (animals A-D) from the same litter (weaned at app. 4 weeks of age) were included in this study. They were obtained from a herd with no history of disease compatible with S. suis infection and S. suis had never been isolated from the herd. For the aerosol exposure, a 1.5 m3 chamber connected to a nebulizing apparatus was used. The chamber and procedure used were essentially as previously described [5]. Briefly, the animals were in the chamber for 20 min while 40 ml of an aquatic solution of 1% acetic acid (pH 3.4) was dispersed and let into the chamber with atmospheric air. Then the pigs were kept outside the chamber for one hour. Thereafter, 3 of the animals (A-C) were brought back into the chamber and 42.5 ml of a bacterial suspension was dispersed over 20 min in the air supply to the chamber. The bacterial suspension was a 5-h broth culture of S. suis serotype 2 (strain P321/6) concentrated to 1.1 × 1010 colony-forming units/ml. The fourth pig (D) served as a control to evaluate the immediate effect of acetic acid alone. One h after exposure to acetic acid in the chamber, this animal was euthanized by exsanguination after being anaesthetized by intramuscular injection (1 ml/15 kg) of Zoletil? (25 mg/ml zolezepam, 25 mg/ml tiletamin). The 3 remaining animals were housed in a single pen and observed for clinical signs of disease and rectal temperatures were recorded daily. On the fifth day after exposure, animal A was euthanized due to the severity of clinical signs. The 2 remaining pigs were euthanized on the sixth day.Following euthanasia, all p
Streptococcal Toxic Shock Syndrome Caused by Streptococcus suis Serotype 2  [PDF]
Jiaqi Tang equal contributor ,Changjun Wang equal contributor,Youjun Feng equal contributor,Weizhong Yang equal contributor,Huaidong Song equal contributor,Zhihai Chen equal contributor,Hongjie Yu equal contributor,Xiuzhen Pan,Xiaojun Zhou,Huaru Wang,Bo Wu,Haili Wang,Huamei Zhao,Ying Lin,Jianhua Yue,Zhenqiang Wu,Xiaowei He,Feng Gao,Abdul Hamid Khan,Jian Wang,Guo-Ping Zhao,Yu Wang ,Xiaoning Wang ,Zhu Chen,George F Gao
PLOS Medicine , 2006, DOI: 10.1371/journal.pmed.0030151
Abstract: Background Streptococcus suis serotype 2 ( S. suis 2, SS2) is a major zoonotic pathogen that causes only sporadic cases of meningitis and sepsis in humans. Most if not all cases of Streptococcal toxic shock syndrome (STSS) that have been well-documented to date were associated with the non-SS2 group A streptococcus (GAS). However, a recent large-scale outbreak of SS2 in Sichuan Province, China, appeared to be caused by more invasive deep-tissue infection with STSS, characterized by acute high fever, vascular collapse, hypotension, shock, and multiple organ failure. Methods and Findings We investigated this outbreak of SS2 infections in both human and pigs, which took place from July to August, 2005, through clinical observation and laboratory experiments. Clinical and pathological characterization of the human patients revealed the hallmarks of typical STSS, which to date had only been associated with GAS infection. Retrospectively, we found that this outbreak was very similar to an earlier outbreak in Jiangsu Province, China, in 1998. We isolated and analyzed 37 bacterial strains from human specimens and eight from pig specimens of the recent outbreak, as well as three human isolates and two pig isolates from the 1998 outbreak we had kept in our laboratory. The bacterial isolates were examined using light microscopy observation, pig infection experiments, multiplex-PCR assay, as well as restriction fragment length polymorphisms (RFLP) and multiple sequence alignment analyses. Multiple lines of evidence confirmed that highly virulent strains of SS2 were the causative agents of both outbreaks. Conclusions We report, to our knowledge for the first time, two outbreaks of STSS caused by SS2, a non-GAS streptococcus. The 2005 outbreak was associated with 38 deaths out of 204 documented human cases; the 1998 outbreak with 14 deaths out of 25 reported human cases. Most of the fatal cases were characterized by STSS; some of them by meningitis or severe septicemia. The molecular mechanisms underlying these human STSS outbreaks in human beings remain unclear and an objective for further study.
Slaughterhouse Pigs Are a Major Reservoir of Streptococcus suis Serotype 2 Capable of Causing Human Infection in Southern Vietnam  [PDF]
Ngo Thi Hoa,Tran Thi Bich Chieu,Tran Thi Thu Nga,Nguyen Van Dung,James Campbell,Pham Hong Anh,Huynh Huu Tho,Nguyen Van Vinh Chau,Juliet E. Bryant,Tran Tinh Hien,Jeremy Farrar,Constance Schultsz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0017943
Abstract: Streptococcus suis is a pathogen of major economic significance to the swine industry and is increasingly recognized as an emerging zoonotic agent in Asia. In Vietnam, S. suis is the leading cause of bacterial meningitis in adult humans. Zoonotic transmission is most frequently associated with serotype 2 strains and occupational exposure to pigs or consumption of infected pork. To gain insight into the role of pigs for human consumption as a reservoir for zoonotic infection in southern Vietnam, we determined the prevalence and diversity of S. suis carriage in healthy slaughterhouse pigs. Nasopharyngeal tonsils were sampled from pigs at slaughterhouses serving six provinces in southern Vietnam and Ho Chi Minh City area from September 2006 to November 2007. Samples were screened by bacterial culture. Isolates of S. suis were serotyped and characterized by multi locus sequence typing (MLST) and pulse field gel electrophoresis (PFGE). Antibiotic susceptibility profiles and associated genetic resistance determinants, and the presence of putative virulence factors were determined. 41% (222/542) of pigs carried S. suis of one or multiple serotypes. 8% (45/542) carried S. suis serotype 2 which was the most common serotype found (45/317 strains, 14%). 80% of serotype 2 strains belonged to the MLST clonal complex 1,which was previously associated with meningitis cases in Vietnam and outbreaks of severe disease in China in 1998 and 2005. These strains clustered with representative strains isolated from patients with meningitis in PFGE analysis, and showed similar antimicrobial resistance and virulence factor profiles. Slaughterhouse pigs are a major reservoir of S. suis serotype 2 capable of causing human infection in southern Vietnam. Strict hygiene at processing facilities, and health education programs addressing food safety and proper handling of pork should be encouraged.
Correlation between PFGE Groups and mrp/epf/sly Genotypes of Human Streptococcus suis Serotype 2 in Northern Thailand  [PDF]
Prasit Tharavichitkul,Kanreuthai Wongsawan,Naoki Takenami,Sumalee Pruksakorn,Achara Fongcom,Marcelo Gottschalk,Banyong Khanthawa,Volaluk Supajatura,Shinji Takai
Journal of Pathogens , 2014, DOI: 10.1155/2014/350416
Abstract: Streptococcus suis infection is a severe zoonotic disease commonly found in Northern Thailand where people often consume raw pork and/or pig’s blood. The most frequent clinical presentations are meningitis, sepsis, and endocarditis with higher rate of mortality and hearing loss sequelae. To clarify the correlation between pulsed-field gel electrophoresis (PFGE) groups and mrp/epf/sly genotypes of S. suis serotype 2, 62 patient and 4 healthy pig isolates from Northern Thailand were studied. By PFGE analysis, at 66% homology, most human isolates (69.4%) and 1 pig isolate were in group A, whereas 14.5% of human isolates and 3 out of 4 pig isolates were in group D. According to mrp/epf/sly genotypes, 80.6% of human isolates were identified in mrp+epf?sly? and only 12.9% were in mrp?epf?sly+ genotypes; in contrast, 1 and 3 pig isolates were detected in these two genotypes, respectively. Interestingly, all isolates of S. suis serotype 2 classified in PFGE groups A, B, and E were set in mrp+epf?sly? genotypes. These data show a close correlation between PFGE groups and mrp/epf/sly genotypes of human S. suis serotype 2. 1. Introduction Streptococcus suis, recognized as a significant swine and human pathogen, mainly causes meningitis, sepsis, endocarditis, and septic shock [1]. It can be transmitted to humans by contact with sick or carrier pigs, pig-derived products [2], or eating undercooked pork [3, 4]. Capsular polysaccharide (CPS) is the most important proven critical virulence factor, due to its antiphagocytosis activity [5]. Of 35 serotypes, serotype 2 is the most frequently isolated and associated with disease in both animals and humans [6]. In addition, virulence-related proteins, such as muramidase-released protein (MRP), extracellular factor (EF), and hemolysin (suilysin, SLY), are expressed by some strains of S. sui “as discussed by Gottschalk and Segura [1].” These proteins are encoded by the genes mrp, epf, and sly, respectively. MRP/EF/SLY phenotypes or mrp/epf/sly genotypes of S. suis serotype 2 have been studied mostly in pig isolates with very little data for human isolates [1, 7], especially in Northern Thailand. Pulsed-field gel electrophoresis (PFGE) of DNA restricted with SmaI has been confirmed to be valuable for evaluating the genetic diversity of S. suis [8]. The present study aims to clarify the correlation between PFGE and mrp/epf/sly genotypes of S. suis serotype 2 isolated from patients in Northern Thailand. 2. Materials and Methods 2.1. S. suis Serotype 2 Strains from Humans and Healthy Pigs A total of 66 S. suis serotype 2 (SS2)
Use of Tetravalent Galabiose for Inhibition of Streptococcus Suis Serotype 2 Infection in a Mouse Model  [PDF]
Roland J. Pieters,Hans-Christian Slotved,Hanne M?ller Mortensen,Lene Arler,Jukka Finne,Sauli Haataja,John A. F. Joosten,Hilbert M. Branderhorst,Karen A. Krogfelt
Biology , 2013, DOI: 10.3390/biology2020702
Abstract: Streptococcus suis is an important swine pathogen associated with a variety of infections such as meningitis, arthritis and septicemia. The bacterium is zoonotic and has been found to cause meningitis especially in humans occupationally exposed to infected pigs. Since adhesion is a prerequisite for colonization and subsequent infection, anti-adhesion treatment seems a natural alternative to traditional treatment with antibiotics. In order to optimize the inhibitory potency a multivalency approach was taken in the inhibitor design. A synthetic tetravalent galabiose compound was chosen which had previously shown promising anti-adhesion effects with S. suis in vitro. The aim of this study was to evaluate the in vivo effects of the compound using an infection peritonitis mouse model. As such S. suis serotype 2 infection and treatment were tested in vivo and the effects were compared to the effect of treatment with penicillin.
Understanding Streptococcus suis serotype 2 infection in pigs through a transcriptional approach
Manli Liu, Liurong Fang, Chen Tan, Tiansi Long, Huanchun Chen, Shaobo Xiao
BMC Genomics , 2011, DOI: 10.1186/1471-2164-12-253
Abstract: A total of 3,002 differentially expressed transcripts were identified in the three tissues, including 417 unique genes in brain, 210 in lung and 213 in PBMC. These genes showed differential expression (DE) patterns on analysis by visualization and integrated discovery (DAVID). The DE genes involved in the immune response included genes related to the inflammatory response (CD163), the innate immune response (TLR2, TLR4, MYD88, TIRAP), cell adhesion (CD34, SELE, SELL, SELP, ICAM-1, ICAM-2, VCAM-1), antigen processing and presentation (MHC protein complex) and angiogenesis (VEGF), together with genes encoding cytokines (interleukins). Five selected genes were validated by qRT-PCR analysis.We studied the response to infection with S. suis 2 strain SC19 by microarray analysis. Our findings confirmed some genes identified in previous studies and discovered numerous additional genes that potentially function in S. suis 2 infections in vivo. This new information will form the foundation of future investigations into the pathogenesis of S. suis.Streptococcus suis (S. suis 2) is an important pathogen of pigs that causes high mortality and is responsible for considerable economic loss to the porcine industry [1]. Serotype 2 is considered the most virulent form of the bacteria and is the serotype most frequently isolated from diseased animals [2]. S. suis 2 is also an emerging zoonotic agent and has been isolated from a wide range of mammalian species, including humans, who are often infected via skin wounds during contact with pigs and their products [3]. S. suis 2 is frequently isolated from asymptomatic pigs, especially adult pigs (young pigs are susceptible to the disease), which indicates that pigs can be carriers of S. suis 2. Two outbreaks in humans have been documented in China, in 1999 and 2005; hundreds of people were infected and 52 died. Human illness following S. suis infection has also been reported in Thailand [4], the United Kingdom [5], the Netherlands [6], Au
Construction and Characterization of a Streptococcus suis Serotype 2 Recombinant Expressing Enhanced Green Fluorescent Protein  [PDF]
Tao Chen, Qin Huang, Zhaolong Li, Wei Zhang, Chengping Lu, Huochun Yao
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0039697
Abstract: Streptococcus suis serotype 2 (S. suis 2) is an important pathogen, responsible for diverse diseases in swine and humans. To obtain a S. suis 2 strain that can be tracked in vitro and in vivo, we constructed the Egfp-HA9801 recombinant S. suis 2 strain with egfp and spcr genes inserted via homologous recombination. To assess the effects of the egfp and spcr genes in HA9801, the biochemical characteristics, growth features and virulence in Balb/C mice were compared between the recombinant and the parent HA9801 strain. We detected the EGFP expression from Egfp-HA9801 by epifluorescence microscopy. The results showed that the biochemical characterization and growth features of the Egfp-HA9801 recombinant were highly similar to that of the parent HA9801. We did not find significant differences in lethality (50% lethal dose), morbidity and mortality between the two strains. Furthermore, the bacterial counts in each various tissues of Egfp-HA9801-infected mice displayed similar dynamic compared with the HA9801-infected mice. Our results also showed that the Egfp-HA9801 cells grown at 37°C for 36 h displayed greater green fluorescence signals than the cells grown at 28°C for 36 h and 37°C for 24 h. The fluorescence in the tissue cryosections of Egfp-HA9801-injected mice was also stronger than that of the HA9801 group. Together, these results indicate that the egfp and spcr insertions into the Egfp-HA9801 recombinant did not significantly change the virulence when compared with HA980, and this EGFP labeled strain can be used for future S. suis 2 pathogenesis research.
Identification and Characterization of a Novel Hemolysis-Related Gene in Streptococcus suis Serotype 2  [PDF]
Jun-xi Zheng, Yue Li, Hui Zhang, Hong-jie Fan, Cheng-ping Lu
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0074674
Abstract: Streptococcus suis serotype 2 (SS 2) is an important zoonotic pathogen that has caused two major infectious outbreaks of streptococcal toxic shock syndrome (STSS) in China. A novel gene located in the 89K pathogenicity island (PAI) encoding a putative hemolysin-III-related protein (Hhly3) has been previously characterized. In this study, the SS2 deletion mutant of the exogenous gene hhly3 was constructed by homologous recombination. This protein was found to exhibit cytolytic activity, and hemolytic activity of the hhly3 gene knockout mutant (Δhhly3) was significantly lower than that in the wild-type strain ZY05719. In addition, qRT-PCR revealed that Hhly3 played an important role in the expression of the secreted hemolysin SLY, which may be the key reason for the decreased hemolytic activity. Consequently, compared with the WT strain, the infection and pathogenicity of Δhhly3 was also decreased, as evidenced by in vitro bacterial growth in whole blood and by the in vivo zebrafish test, suggesting that hhly3 is a novel exogenous hemolysis-related gene in SS2 strains.
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