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PubMed2004

Streptococcus suis meningitis in Thailand.

Streptococcus suis may be the second most common cause of adult streptococcal meningitis. The clinical and epidemiological data of S. suis meningitis are occasionally reviewed. To date, there have been only two large case series from Hong Kong and the Netherlands. We describe twelve cases of S. suis meningitis who were admitted to Chulalongkorn University Hospital, Bangkok, during a 6-year period between 1997 and 2002. A comparative review of case reports of S. suis meningitis in Thailand, Hong Kong, and the Netherlands is presented and revealed no significant differences between the three series. However, the cases from Thailand and Hong Kong had a significantly greater number of associated skin and soft tissue infections. Clinically, S. suis meningitis may appear acute or with a more chronic course.

Adult↗

PubMed2006

Phagocytosis and killing of Streptococcus suis by porcine neutrophils.

Streptococcus suis serotype 2 is an important swine pathogen responsible for diverse infections, mainly meningitis. Virulence factors and the pathogenesis of infection are not well understood. Neutrophils may play an important role in the pathogenesis of infection given that infiltration by neutrophils and mononuclear cells are frequently observed in lesions caused by S. suis. The objective of this work was to study the interactions between S. suis serotype 2 and porcine neutrophils. Results showed that suilysin is toxic to neutrophils and this could help S. suis evade innate immunity. Moreover, suilysin appears to affect complement-dependent killing by decreasing the opsonization of S. suis and the bactericidal capacity of neutrophils. Our results confirm that capsule polysaccharide protects S. suis against killing and phagocytosis by neutrophils. We also showed that the presence of specific IgG against S. suis serotype 2 promoted killing by neutrophils, indicating that the induction of a strong humoral response is beneficial for clearance of this pathogen.

Animals↗

PubMed1994

Partial characterization of Streptococcus suis type 2 hemolysin.

Streptococcus suis type 2 was evaluated for hemolysin production. Supernatants of S. suis type 2 grown in Todd-Hewitt broth were assayed for hemolytic activity by a photometric assay. Twenty-two additional serotypes of S. suis (1,3 to 22, and 1/2) were evaluated for hemolysin production; nine of them (1/2, 1, 4, 5, 14, 15, 17, 19, and 20) were positive. The effects of temperature, atmosphere, centrifugation, sonication, chemicals, bovine serum albumin, fetal calf serum, and enzymes on S. suis type 2 hemolysin activity were studied. Maximum hemolysis occurred after incubation in RPMI 1640 medium at 40 degrees C in 6% CO2 and after growth in Todd-Hewitt broth at 37 degrees C under anaerobic conditions. Hemolytic activity was absent after the addition of fetal calf serum and decreased after the addition of trypsin or amylase. However, treatment of erythrocytes with amylase or trypsin prior to incubation with supernatant also resulted in a decrease in hemolytic activity. The addition of bovine serum albumin caused increased hemolytic activity. Dipyridyl and EDTA had negligible effects on hemolysis. Hemolytic S. suis type 2 culture supernatant injected intraperitoneally failed to cause death in BALB/c mice. Data from our study indicate that S. suis type 2 hemolysin is a secreted or loosely cell bound, thermolabile molecule whose activity is growth condition dependent.

Animals↗

PubMed2004

Non-encapsulated strains reveal novel insights in invasion and survival of Streptococcus suis in epithelial cells.

Streptococcus suis is a porcine and human pathogen causing invasive diseases, such as meningitis or septicaemia. Host cell interactions of S. suis have been studied mainly with serotype 2 strains, but multiple capsular serotypes as well as non-typeable strains exist with diverse virulence features. At present, S. suis is considered an extracellular pathogen. However, whether or not it can also invade host cells is a matter of controversial discussions. We have assessed adherence and invasion of S. suis for HEp-2 epithelial cells by comparing 10 serotype 2 strains and four non-typeable (NT) strains. Only the NT strains and a non-encapsulated serotype 2 mutant strain, but none of the serotype 2 strains, adhered strongly and were invasive. Invasion seemed to be affected by environmental signals, as suggested from comparison of strains grown in different media. Further phenotypic and genotypic characterization revealed a high diversity among the different strains. Electron microscopic analysis of invasion of selected invasive NT strains indicated different uptake mechanisms. One strain induced large invaginations comparable to those seen in 'caveolae' mediated uptake, whereas invasion of the other strains was accompanied by formation of filipodia-like membrane protrusions. Invasion of all strains, however, was similarly susceptible to hypertonic sucrose, which inhibits receptor-mediated endocytosis. Irrespective of the uptake pathway, streptococci resided in acidified phago-lysosome like vacuoles. All strains, except one, survived intracellularly as well as extracellular acidic conditions. Survival seemed to be associated with the AdiS protein, an environmentally regulated arginine deiminase of S. suis. Concluding, invasion and survival of NT strains of S. suis in epithelial cells revealed novel evidence that S. suis exhibits a broad variety of virulence-associated features depending on genetic variation and regulation.

Acids↗

PubMed2002

CD14-dependent and -independent cytokine and chemokine production by human THP-1 monocytes stimulated by Streptococcus suis capsular type 2.

Streptococcus suis capsular type 2 is an important aetiologic agent of swine meningitis, and it has been highlighted as a cause of occupational disease leading to meningitis and fulminant sepsis in humans. The objective of the present work was to study the ability of S. suis type 2 to induce the release of tumour necrosis factor alpha (TNF-alpha), interleukin-1 (IL-1), IL-6, IL-8 and monocyte chemotactic protein one (MCP-1) by human monocytic THP-1 cells. The induction of these five cytokines was dose- and incubation time-dependent, and it was significantly enhanced by pre-treatment of cells with interferon gamma. IL-8 levels were markedly higher compared with those obtained with the other cytokines. However, elevated levels of MCP-1 and IL-6 were also observed. Levels of cytokine induced by heat-killed or live bacteria were similar. Pre-treatment of cells with anti-CD14 monoclonal antibodies suggested that this important host receptor is partially implicated in TNF, IL-1, IL-6 and MCP-1 production, while CD14-independent pathways seem to be responsible for IL-8 production after S. suis stimulation. In addition, blocking studies with anti-TNF and anti-IL-1 antibodies revealed that these cytokines are involved in amplification of the S. suis-induced cytokine cascade. When several different S. suis strains of human or porcine origin were compared, a very heterogeneous pattern of cytokine production was observed. Human strains did not exhibit a clear tendency to induce higher cytokine release by human THP-1 monocytes. The synergistic effect of the up-regulation of cytokines during S. suis meningitis may mediate many of the inflammatory reactions, including the sequestration of leucocytes at the site of infection.

Animals↗

PubMed2006

Streptococcus suis in Hong Kong.

Streptococcus suis was isolated from 6.1% of raw pork meat from 3 of the 6 wet markets in 6 districts in Hong Kong. S. suis was particularly isolated in sites from the tongue, tonsil, bone, and tail, but not from lean meat/minced pork or internal organs. Isolates were confirmed by polymerase chain reaction using S. suis-specific primers, did not belong to serotype 2 using serotype 2-specific antiserum, and were clustered closely with other known serotypes by phylogenetic analysis. Ten strains from patients admitted to Hong Kong hospitals with sepsis or meningitis in the past 10 years all belonged to type 2, with closely related pulsed-field gel electrophoresis types that were distinct from the S. suis strains isolated from pork in this study. These methods may serve as useful tools in studying and enhancing our understanding of these infections in Hong Kong.

Animals↗

PubMed2005

Prevalence of the suilysin gene in Streptococcus suis strains isolated from diseased and healthy carrier pigs.

Knowledge of virulence factors of Streptococcus suis is limited. Several virulence factor candidates have been proposed, among them suilysin, which is responsible for a toxic effect on epithelial cells. The aim of this study was to detect the suilysin gene sequence in Streptococcus suis strains of various origin. In total 63 Streptococcus suis isolates were investigated. Forty four of them originated from tissues of streptococcosis affected animals. The remaining 19 strains were isolated from tonsils of healthy carrier pigs. Suilysin gene specific sequence was detected in 79% of the strains tested. In isolates obtained from pigs with signs of streptococcosis this gene sequence was recorded in 85% of cases. In Streptococcus suis strains isolated from healthy carrier pigs the suilysin gene was detected in 63% of the isolates. It seems that suilysin toxic activity is only one of the many steps involved in the pathogenesis of Streptococcus suis infection and that strain's virulence cannot be stated only on the basis of suilysin gene sequence presence.

Animals↗

PubMed2005

[Detection of virulence-associated factors of Streptococcus suis by multiplex PCR assay].

OBJECTIVE: To rapidly and sensitively detect the four virulence-associated factors of Streptococcus suis, a multiplex PCR was developed. METHODS: In the process of this reaction, four distinct DNA targets were amplified. One target was based on the serotype 2 (and 1/2) specific cps gene and the others were based on Streptococcus suis mrp, epf (epf*) and sly gene, encoding the MRP, EF(EF*) and Sly proteins of Streptococcus suis. 72 isolates, which including 48 strains of Streptococcus suis and 24 strains of negative control, and 49 clinical specimens were detected by the multiplex PCR assay. RESULTS: All PCR products were detected by electrophoresis on 1.2% agarose gels. With the 48 Streptococcus suis strains, the positive detection rates of cps2+, mrp+, epf+, epf*+ and sly+ were 16/48, 14/48, 12/48, 3/48 and 26/48,respectively. The results were confirmed by bacteriological examination. There were no specific amplification products including 49 clinical specimens and 24 negative control strains. CONCLUSION: The results demonstrated that multiplex PCR was a highly specific and sensitive diagnostic tool for the detection of virulence-associated factors of streptococcus suis.

Bacterial Proteins↗

PubMed2005

[Matched case-control study for risk factors of human Streptococcus suis infection in Sichuan Province, China].

OBJECTIVE: To study the potential risk factors of human infecting with Streptococcus suis. METHODS: 1: M matched case-control study was conducted. 29 human cases of Streptococcus suis infection in the early phase were included in the case group, Patients' family members, neighbors and peoples who had worked together with patients to handle deceased or sick pigs in the last week were recruited as matched controls. There were 147 controls in total. Both cases and controls received questionnaire investigation including the ways to contact sick/dead pigs. Conditional logistic regression was employed to analyze matching data. RESULTS: According to the results of multivariate analysis, slaughtering (OR = 11.978, 95% CI: 3.355-42.756), carcasses cutting and processing (OR = 3.008, 95% CI: 1.022-8.849) sick/dead pigs were associated with cases related to human Streptococcus suis infection. The attributable risk proportion were 91.65% and 66.76% respectively. The other types of exposures to sick/ dead pigs, including feeding, selling, burying and eating, were not associated with the human Streptococcus suis infection in our study population. CONCLUSION: Slaughtering, carcasses cutting and processing sick/dead pigs were important risky behavior for humans to be infected by Streptococcus suis.

Adult↗

PubMed2005

Biochemical analysis, cpn60 and 16S rDNA sequence data indicate that Streptococcus suis serotypes 32 and 34, isolated from pigs, are Streptococcus orisratti.

Streptococcus suis serotypes have traditionally been identified by morphology, biochemical profiling and serotyping. Analysis of the sequences of 16S rRNA and cpn60 genes of the 35 characterized serotypes of S. suis led to the observation that two serotypes 32 and 34, are significantly distinct from other S. suis serotypes and may represent a distinct species. Here we present DNA sequence data and biochemical profiles which indicate that S. suis serotypes 32 and 34, isolated from pigs, are clustered with Streptococcus orisratti, a Voges-Proskauer negative, alpha-haemolytic, aesculin-hydrolytic, Lancefield group A streptococcus isolated from the teeth of rats.

Animals↗

PubMed1996

Evaluation of antibiotics for the elimination of the tonsillar carrier state of Streptococcus suis in pigs.

Seventy clinically normal 13-day-old crossbred pigs from 10 litters from a Streptococcus suis-infected herd were randomly assigned by litter and weight to 7 groups of 10 pigs each to determine whether different antibiotic regimens would eliminate the tonsillar carrier state of S. suis. Six antimicrobial regimens were tested: penicillin intramuscularly (IM) once daily (s.i.d.) for 3 consecutive days; penicillin IM s.i.d. for 5 consecutive days; ampicillin IM s.i.d. for 5 consecutive days; ampicillin per os s.i.d. for 5 consecutive days; ampicillin intranasally s.i.d. for 5 consecutive days; and ceftiofur sodium IM s.i.d. for 5 consecutive days. The seventh group consisted of untreated control pigs. Tonsillar swab samples were collected before treatment, and tonsillar tissue samples were collected after treatment for cultural examination for S. suis. Streptococcus suis was identified in pigs from all groups prior to treatment and after treatment. Pigs did not have clinical signs of disease during the study. All antimicrobial treatments tested in this study failed to eliminate the tonsillar carrier state of S. suis. Early weaning and medication used in this study were not effective for the elimination of the tonsillar carrier state of S. suis in pigs. Optimization of management and environment of pigs coupled with strategic medication of clinically ill animals should be used for control and prevention of mortality caused by streptococcosis.

Administration, Intranasal↗

PubMed2005

Different foreign genes incidentally integrated into the same locus of the Streptococcus suis genome.

Some strains of Streptococcus suis possess a type II restriction-modification (RM) system, whose genes are thought to be inserted into the genome between purH and purD from a foreign source by illegitimate recombination. In this study, we characterized the purHD locus of the S. suis genomes of 28 serotype reference strains by DNA sequencing. Four strains contained the RM genes in the locus, as described before, whereas 11 strains possessed other genetic regions of seven classes. The genetic regions contained a single gene or multiple genes that were either unknown or similar to hypothetical genes of other bacteria. The mutually exclusive localization of the genetic regions with the atypical G+C contents indicated that these regions were also acquired from foreign sources. No transposable element or long-repeat sequence was found in the neighboring regions. An alignment of the nucleotide sequences, including the RM gene regions, suggested that the foreign regions were integrated by illegitimate recombination via short stretches of nucleotide identity. By using a thermosensitive suicide plasmid, the RM genes were experimentally introduced into an S. suis strain that did not contain any foreign genes in that locus. Integration of the plasmid into the S. suis genome did not occur in the purHD locus but occurred at various chromosomal loci, where there were 2 to 10 bp of nucleotide identity between the chromosome and the plasmid. These results suggest that various foreign genes described here were incidentally integrated into the same locus of the S. suis genome.

Animals↗

PubMed2005

Adherence of Streptococcus suis to porcine endothelial cells.

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

Animals↗

PubMed2001

[Streptococcus suis meningitis].

Human infection by Streptococcus suis (S. suis) is a zoonosis, with a known occupational risk and clinical presentation mainly as a purulent meningitis with low mortality and frequent hearing loss and ataxia sequela. Less than 150 human cases have been reported since original one thirty years ago. There is a geographical distribution most patients living in northern Europe and south Asia. S. suis disease in human has been reported in two patients in Spain the last years. We present two patients with S. suis meningitis, both were men with occupation related by pork meet, and good outcome. They come at our hospital in a lapse of one month. Both had neurosensorial hearing loss and walking ataxia. One patient had peripheral facial paralysis and diplopia because of paresia of contralateral sixth nerve, with complete resolution at three months. The rare presentation of S. suis meningitis in our country must not forget us to record the working risk at anamnesis.

Adult↗

PubMed2001

Prevalence and mechanism of resistance against macrolides and lincosamides in Streptococcus suis isolates.

Eighty-seven Streptococcus suis isolates recovered in 1999-2000 from diseased pigs, all from different farms, were screened for resistance against macrolide and lincosamide antibiotics by the disk diffusion and agar dilution test and a PCR assay, amplifying the ermB gene and the mefA/E gene. Seventy-one percent of the isolates showed constitutive resistance to macrolide and lincosamide antibiotics (MLS(B)-phenotype). All these isolates were positive for the ermB gene in the PCR, but negative for the mefA/E gene. For all strains minimum inhibitory concentrations (MIC) against five other antimicrobial agents were determined. All strains were susceptible to penicillin. Ninety-nine percent of the isolates were susceptible to enrofloxacin and tiamulin. Eighty-five percent of the strains were resistant to doxycycline. A 540bp fragment of the ermB genes of eight S. suis strains was sequenced and compared with ermB genes of five S. pneumoniae and five S. pyogenes strains of human origin. A 100% homology was found between these fragments in seven S. suis, one S. pneumoniae and three of the S. pyogenes isolates. This study demonstrates that resistance against macrolides, lincosamides and streptogramin B is widespread in S. suis and mediated by ribosome methylation, encoded by the ermB gene.

Animals↗

PubMed1998

Use of ribotyping and hemolysin activity to identify highly virulent Streptococcus suis type 2 isolates.

Nineteen Streptococcus suis type 2 isolates were evaluated for their virulence in pigs and mice. Of these, seven were determined to be highly virulent in pigs on the basis of clinical sign scores and gross pathology and histopathology results. Clinical sign scores correlated with gross pathology and histopathology scores at P equal to 0.004 and P equal to 0.009, respectively. The virulence of highly virulent isolates in pigs compared somewhat with virulence in mice, but the correlation was not significant. No correlation of virulence was noted among the moderately virulent and avirulent isolates in pigs and mice. Chromosomal DNAs from all S. suis isolates were evaluated by PstI, PvuII, EcoRI, and HaeIII restriction enzyme digestion followed by hybridization with a digoxigenin-11-dUTP-labeled cDNA probe transcribed from 16S and 23S rRNAs from Escherichia coli. The hybridization patterns (ribotypes) varied depending upon the enzyme used, but a significant number of isolates determined to be highly virulent in pigs had unique hybridization patterns compared with those of the moderately virulent and avirulent isolates (P = 0.002). In addition, hemolysin activity showed a high correlation to virulence (P = 0.00008) and ribotype (P = 0.002).

Animals↗

PubMed1994

Characterization of antibiotic resistance in Streptococcus suis.

Twenty one isolates of Streptococcus suis were screened for antibiotic resistance by growth on antibiotic-containing media, by measuring minimum inhibitory concentrations, by hybridization to specific DNA and oligonucleotide probes for antibiotic resistance genes, and by PCR. The isolates were from a slaughter house survey of respiratory pathogens in Norwegian pigs in 1986. Fifteen isolates were resistant to tetracycline, with MICs ranging from 4-128 micrograms/ml. Genes coding for the Tet O and Tet M determinants were detected in eight and five isolates, respectively. Genes coding for other Gram positive Tet determinants, Tet K, Tet L, and Tet P, were not detected. One isolate was constitutive resistant to erythromycin with MIC of 128 micrograms/ml. Five other isolates carried inducible erythromycin resistance. All these isolates, and five others, were positive in a PCR assay for erythromycin resistance, and hybridized with the Erm C and/or Erm B probes. No resistance against chloramphenicol (5 micrograms/ml) or rifampin (10 micrograms/ml) could be could be detected, but five isolates were resistant to streptomycin (250 micrograms/ml), four isolates were resistant to kanamycin (10 micrograms/ml), and one isolate was resistant to fusicic acid (10 micrograms/ml). In mating experiments with Enterococcus faecalis JH2-2 as recipient, tetracycline, erythromycin, and kanamycin genes were transferred separately to the recipient strain at a rate of 10(-7) transconjugants/recipient cell.

Animals↗

PubMed1990

Infective endocarditis caused by Streptococcus suis serotype 2.

Infective endocarditis caused by Streptococcus suis serotype 2 is not uncommon in pigs but is rare in human beings. We describe the case of a pig-farmer with endocarditis due to S. suis serotype 2 and in whom prolapse of the mitral valve was the predisposing cardiac lesion. Streptococcus suis, a possible cause of infective endocarditis in endemic areas, may be confused with other group D streptococci. In suspected cases a history of contact with pigs or raw pork should be sought.

Agricultural Workers' Diseases↗