The SspA subtilisin-like protease of Streptococcus suis triggers a pro-inflammatory response in macrophages through a non-proteolytic mechanism

<p>Abstract</p> <p>Background</p> <p><it>Streptococcus suis </it>is a major swine pathogen worldwide that causes meningitis, septicemia, arthritis, and endocarditis. Using animal models, a surface-associated subtilisin-like protease (SspA) has recently been shown to be an important virulence factor for <it>S. suis</it>. In this study, we hypothesized that the <it>S. suis </it>SspA subtilisin-like protease may modulate cytokine secretion by macrophages thus contributing to the pathogenic process of meningitis.</p> <p>Results</p> <p>Phorbol 12-myristate 13-acetate-differentiated U937 macrophages were stimulated with recombinant SspA prior to monitor cytokine secretion by ELISA. Our results indicated that the recombinant SspA was able to dose-dependently induce IL-1β, IL-6, TNF-α, CXCL8 and CCL5 secretion in macrophages. The heat-inactivated protease was still able to induce cytokine secretion suggesting a non-proteolytic mechanism of macrophage activation. Using specific kinase inhibitors, evidence were bought that cytokine secretion by macrophages stimulated with the recombinant SspA involves the mitogen-activated protein kinase signal transduction pathway. While stimulation of macrophages with low concentrations of recombinant SspA was associated to secretion of high amounts of CCL5, the use of recombinant SspA at a high concentration resulted in low amounts of CCL5 detected in the conditioned medium. This was found to be associated with a proteolytic degradation of CCL5 by SspA. The ability of SspA to induce cytokine secretion in macrophages was confirmed using a mutant of <it>S. suis </it>deficient in SspA expression.</p> <p>Conclusion</p> <p>In conclusion, this study identified a new mechanism by which the <it>S. suis </it>SspA may promote central nervous system inflammation associated with meningitis.</p

Caractérisation de nouveaux facteurs de virulence chez Streptococcus suis

Les cas d'infections à Streptococcus suis sont très répandus dans tous les pays producteurs de porcs. Cet organisme est également reconnu comme un agent de zoonose pour les personnes en contact étroit avec les porcs ou leurs produits dérivés. De nombreux rapports indiquent que depuis le début des années soixante-dix, le nombre de cas d'infections ainsi que la gravité des infections à S. suis ont considérablement augmenté. Un temps d'incubation plus court, une progression plus rapide de la maladie, un taux plus élevé de mortalité soulignent la nécessité urgente de mieux comprendre les facteurs associés à la pathogenèse de l'infection par S. suis. Des 35 serotypes décrits, le serotype 2 demeure le plus fréquemment associé à un phénomène de septicémie et à des cas de maladies telles que les méningites, endocardites et pneumonies. C'est également le serotype le plus souvent retrouvé chez l'humain et le porc. La pathogenèse de l'infection causée par S. suis est encore relativement mal connue. La présence d'une capsule riche en acide sialique est classiquement considérée comme un facteur de virulence essentiel, mais récemment d'autres facteurs ont également été cités. Cette étude avait pour but d'identifier et de caractériser de nouveaux déterminants de virulence chez S. suis. Dans un premier temps, la capacité de S. suis à former un biofilm a été étudiée. Il a été démontré que la présence de fibrinogène pouvait induire la formation d'un biofilm chez S. suis. Un mutant déficient pour l'expression de la capsule de même que des souches non-sérotypables de S. suis dépourvues de capsule ont montré une capacité de former un biofilm sans apport de fibrinogène. Il a été suggéré que la capsule chez S. suis pourait cacher des adhésines de surface et ainsi interférer avec la formation du biofilm et les capacités d'adhésion. Dans un second temps, l'utilisation d'un mutant de S. suis déficient pour une pseudo-subtilisine a permis de démontrer le rôle critique de cette protease pour le développement d'une infection dans un modèle de souris. La pseudo-subtilisine de S. suis a été clonée, purifiée et caractérisée. Certaines protéines de l'hôte comme le fibrinogène se sont révélées susceptibles à la protease. Une stimulation de macrophages par la pseudo-subtilisine recombinante a induit à une forte sécrétion de cytokines pro-inflammatoires. Lors d'infections expérimentales à S. suis chez le porc, les animaux ont développé des anticorps dirigés contre la pseudo-subtilisine, suggérant ainsi que cette protease représente un immunogène d'intérêt pour la vaccination. Enfin, un nouveau modèle pour l'analyse de la virulence de S. suis a été mis au point utilisant l'amibe Dictyostelium discoideum. Ce modèle a mis en évidence des différences majeures entre des souches sauvages virulentes de S. suis et des mutants ayant une virulence atténuée dans des modèles animaux classiques. En conclusion, ce projet a permis d'améliorer nos connaissances des mécanismes étiopathogéniques des infections à S. suis et a ouvert de nouvelles perspectives de prévention et traitement de ces infections

Detection of streptococcus suis in bioaerosols of swine confinement buildings

Streptococcus suis is an important swine pathogen that can cause septicemia, meningitis, and pneumonia. Also recognized as an emerging zoonotic agent, it is responsible for outbreaks of human infections in Asian countries. Serotype 2 is the predominant isolate from diseased animals and humans. The aerosolization of S. suis in the air of swine confinement buildings (SCB) was studied. The presence of S. suis in bioaerosols was monitored in SCB where cases of infection had been reported and in healthy SCB without reported infections. Using a quantitative-PCR (qPCR) method, we determined the total number of bacteria (1 × 108 to 2 × 108 airborne/m3), total number of S. suis bacteria (4 × 105 to 10 × 105 airborne/m3), and number of S. suis serotype 2 and 1/2 bacteria (1 × 103 to 30 × 103 airborne/m3) present in the air. S. suis serotypes 2 and 1/2 were detected in the air of all growing/finishing SCB that had documented cases of S. suis infection and in 50% of healthy SCB. The total number of bacteria and total numbers of S. suis and S. suis serotype 2 and 1/2 bacteria were monitored in one positive SCB during a 5-week period, and it was shown that the aerosolized S. suis serotypes 2 and 1/2 remain airborne for a prolonged period. When the effect of aerosolization on S. suis was observed, the percentage of intact S. suis bacteria (showing cell membrane integrity) in the air might have been up to 13%. Finally S. suis was found in nasal swabs from 14 out of 21 healthy finishing-SCB workers, suggesting significant exposure to the pathogen. This report provides a better understanding of the aerosolization, prevalence, and persistence of S. suis in SCB

Detection and quantification of airborne norovirus during outbreaks in healthcare facilities

Background. Noroviruses are responsible for at least 50% of all gastroenteritis outbreaks worldwide. Noroviruses GII can infect humans via multiple routes including direct contact with an infected person, fecal matter, or vomitus, and contact with contaminated surfaces. Although norovirus is an intestinal pathogen, aerosols could, if inhaled, settle in the pharynx and later be swallowed. The aims of this study were to investigate the presence of norovirus GII bioaerosols during gastroenteritis outbreaks in healthcare facilities and to study the in vitro effects of aerosolization and air sampling on the noroviruses using murine norovirus as a surrogate. Methods. A total of 48 air samples were collected during norovirus outbreaks in 8 healthcare facilities. Samples were taken 1 m away from each patient, in front of the patient's room and at the nurses' station. The resistance to aerosolization stress of murine norovirus type 1 (MNV-1) bioaerosols was also tested in vitro using an aerosol chamber. Results. Norovirus genomes were detected in 6 of 8 healthcare centers. The concentrations ranged from 1.35 × 101 to 2.35 × 103 genomes/m3 in 47% of air samples. MNV-1 preserved its infectivity and integrity during in vitro aerosol studies. Conclusions. Norovirus genomes are frequently detected in the air of healthcare facilities during outbreaks, even outside patients' rooms. In addition, in vitro models suggest that this virus may withstand aerosolization

Tell me if you prefer bovine or poultry sectors and I’ll tell you who you are: Characterization of Salmonella enterica subsp. enterica serovar Mbandaka in France

IntroductionIn north-western France, Salmonella enterica susp. enterica serovar Mbandaka (S. Mbandaka) is most frequently isolated from bovine and dairy samples. While this serovar most often results in asymptomatic carriage, for a number of years it has caused episodes of abortions, which have serious economic consequences for the sector. Interestingly, this serovar is also isolated from Gallus gallus in the same geographic zone. Despite its prevalence in bovines in north-western France, S. Mbandaka has not been broadly studied at the genomic level, and its prevalence and host adaptation are still not fully understood.MethodsIn this study, we analyzed the genomic diversity of 304 strains of S. Mbandaka isolated from the bovine and poultry sectors in this area over a period of 5 years. A phylogenetic analysis was carried out and two approaches were followed to identify conserved genes and mutations related to host associations. The first approach targeted the genes compiled in the MEGARESv2, Resfinder, VFDB and SPI databases. Plasmid and phage contents were also investigated. The second approach refers to an in-house algorithm developed for this study that computes sensitivity, specificity, and accuracy of accessory genes and core variants according to predefined genomes groups.Results and discussionAll the analyzed strains belong to the multi-locus sequence type profile ST413, and the phylogenomic analysis revealed main clustering by host (bovine and poultry), emphasizing the circulation of 12 different major clones, of which seven circulate in poultry and five in the bovine sector in France and a likely food production chain adaptation of these clones. All strains present resistance determinants including heavy metals and biocides that could explain the ability of this serovar to survive and persist in the environment, within herds, and in food processing plants. To explore the wild animal contribution to the spread of this serovar in north-western France, we retrieved S. Mbandaka genomes isolated from wild birds from EnteroBase and included them in the phylogenomic analysis together with our collection. Lastly, screening of accessory genes and major variants allowed us to identify conserved specific mutations characteristic of each major cluster. These mutations could be used to design useful probes for food safety surveillance

Cranberry polyphenols: potential benefits for dental caries and periodontal disease

ABSTRACT Over the past decade, cranberries and their molecular components have received increasing attention from researchers in human health. In particular, the properties of the high-molecular-weight polyphenols isolated from cranberries have shown promise with regard to dental caries and periodontal disease. These potential anticaries agents inhibit the production of organic acids and the formation of biofilms by cariogenic bacteria. In addition, cranberry polyphenols may reduce the inflammatory response, as well as the production and activity of proteolytic enzymes contributing to the destruction of the extracellular matrix in periodontal disease. The polyphenols of cranberries also interfere with various activities (including formation of biofilm and adhesion) of Porphyromonas gingivalis, the main etiologic agent in chronic periodontitis. This article summarizes the scientific evidence supporting the potential of cranberry polyphenols to prevent and/or treat diseases of the mouth

Fibrinogen Induces Biofilm Formation by Streptococcus suis and Enhances Its Antibiotic Resistance▿

In this study, we showed that supplementing the culture medium with fibrinogen induced biofilm formation by Streptococcus suis in a dose-dependent manner. Biofilm-grown S. suis cells were much more resistant to penicillin G than planktonic cells. S. suis bound fibrinogen to its surface, a property that likely contributes to biofilm formation

Preferential aerosolization of Streptococcus suis

Streptococcus suis is a swine pathogen that causes pneumonia, septicaemia and meningitis. It is also an important zoonotic agent responsible of several outbreaks in China. S. suis strains are classified into 35 serotypes based on the composition of their polysaccharide capsule. S. suis serotype 2 causes the majority of severe infections and it is subdivided into sequence types (STs) based on multilocus sequence typing. The ST1 is associated with highly virulent strains. In North America, the strains most commonly isolated belong to ST25 and ST28, which are respectively moderately and weakly virulent in a mouse model. The presence of S. suis bioaerosols in the air of swine confinement buildings has been previously demonstrated. The aim of this study was to better understand the aerosolization behaviour of S. suis by investigating of the preferential aerosolization of different strains of S. suis. The highly virulent serotype 2 ST1 strains appeared to be preferentially aerosolized. This study increases our knowledge on the potential aerosol transmission of S. suis and emphasises the importance of developing an exposure prevention strategy to protect the swine and the swine producers