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Positive- and Negative-Control Pathways by Blood Components for Intermedilysin Production in Streptococcus intermedius.

ABSTRACT: Streptococcus intermedius is an opportunistic bacterial pathogen secreting a human-specific cytolysin called intermedilysin (ILY) as a major pathogenic factor. This bacterium can degrade glycans into monosaccharides using two glycosidases, multisubstrate glycosidase A (MsgA) and neuraminidase (NanA). Here, we detected a stronger hemolytic activity mediated by ILY when S. intermedius PC574 was cultured in fetal bovine serum (FBS) than when it was grown in the standard culture medium. FBS-cultured cells also showed higher MsgA and NanA activity, although overproduction of ILY in FBS was undetectable in mutants nanA-null and msgA-null. Addition of purified MsgA and NanA to the FBS resulted in a release of 2.8 mM galactose and 4.3 mM N-acetylneuraminic acid; these sugar concentrations were sufficient to upregulate the expression of ILY, MsgA, and NanA. Conversely, when strain PC574 was cultured in human plasma, no similar increase in hemolytic activity was observed. Moreover, addition of human plasma to the culture in FBS appeared to inhibit the stimulatory effect of FBS on ILY, MsgA, and NanA, although there were individual differences among the plasma samples. We confirmed that human plasma contains immunoglobulins that can neutralize ILY, MsgA, and NanA activities. In addition, human plasma had a neutralizing effect on cytotoxicity of S. intermedius toward HepG2 cells in FBS, and a higher concentration of human plasma was necessary to reduce the cytotoxicity of an ILY-high-producing strain than an ILY-low-producing strain. Overall, our data show that blood contains factors that stimulate and inhibit ILY expression and activity, which may affect pathogenicity of S. intermedius.

SUBMITTER: Tomoyasu T

PROVIDER: S-EPMC5563582 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Positive- and Negative-Control Pathways by Blood Components for Intermedilysin Production in Streptococcus intermedius.

Tomoyasu Toshifumi T Yamasaki Takahiro T Chiba Shinya S Kusaka Shingo S Tabata Atsushi A Whiley Robert A RA Nagamune Hideaki H

Infection and immunity 20170818 9

<i>Streptococcus intermedius</i> is an opportunistic bacterial pathogen secreting a human-specific cytolysin called intermedilysin (ILY) as a major pathogenic factor. This bacterium can degrade glycans into monosaccharides using two glycosidases, multisubstrate glycosidase A (MsgA) and neuraminidase (NanA). Here, we detected a stronger hemolytic activity mediated by ILY when <i>S. intermedius</i> PC574 was cultured in fetal bovine serum (FBS) than when it was grown in the standard culture medium ...[more]

PMID: 28607101

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Project description:BackgroundStreptococcus intermedius, a member of the S. anginosus group, is a commensal bacterium present in the normal microbiota of human mucosal surfaces of the oral, gastrointestinal, and urogenital tracts. However, it has been associated with various infections such as liver and brain abscesses, bacteremia, osteo-articular infections, and endocarditis. Since 2005, high throughput genome sequencing methods enabled understanding the genetic landscape and diversity of bacteria as well as their pathogenic role. Here, in order to determine whether specific virulence genes could be related to specific clinical manifestations, we compared the genomes from 27 S. intermedius strains isolated from patients with various types of infections, including 13 that were sequenced in our institute and 14 available in GenBank.ResultsWe estimated the theoretical pangenome size to be of 4,020 genes, including 1,355 core genes, 1,054 strain-specific genes and 1,611 accessory genes shared by 2 or more strains. The pangenome analysis demonstrated that the genomic diversity of S. intermedius represents an "open" pangenome model. We identified a core virulome of 70 genes and 78 unique virulence markers. The phylogenetic clusters based upon core-genome sequences and SNPs were independent from disease types and sample sources. However, using Principal Component analysis based on presence/ absence of virulence genes, we identified the sda histidine kinase, adhesion protein LAP and capsular polysaccharide biosynthesis protein cps4E as being associated to brain abscess or broncho-pulmonary infection. In contrast, liver and abdominal abscess were associated to presence of the fibronectin binding protein fbp54 and capsular polysaccharide biosynthesis protein cap8D and cpsB.ConclusionsBased on the virulence gene content of 27 S. intermedius strains causing various diseases, we identified putative disease-specific genetic profiles discriminating those causing brain abscess or broncho-pulmonary infection from those causing liver and abdominal abscess. These results provide an insight into S. intermedius pathogenesis and highlights putative targets in a diagnostic perspective.

Project description:Streptococcus intermedius, an oral commensal bacterium, is found at various sites, including subgingival dental plaque, purulent infections, and cystic fibrosis lungs. Oral streptococci utilize proteins on their surface to adhere to tissues and/or surfaces localizing the bacteria, which subsequently leads to the development of biofilms, colonization, and infection. Among the 19 genomically annotated cell wall-attached surface proteins on S. intermedius, Pas is an adhesin that belongs to the antigen I/II (AgI/II) family. Here, we have structurally and functionally characterized Pas, particularly focusing on its microbial-host as well as microbial-microbial interactions. The crystal structures of VPas and C123Pas show high similarity with AgI/II of Streptococcus mutans. VPas hosts a conserved metal binding site, and likewise, the C123Pas structure retains its conserved metal binding sites and isopeptide bonds within its three DEv-IgG domains. Pas interacts with nanomolar affinity to lung alveolar glycoprotein 340 (Gp340), its scavenger receptor cysteine-rich domains (SRCRs), and with fibrinogen. Both Candida albicans and Pseudomonas aeruginosa, the opportunistic pathogens that cohabitate with S. intermedius in the lungs of CFTR patients were studied in dual-species biofilm studies. The Pas-deficient mutant (Δpas) displayed significant reduction in dual-biofilm formation with C. albicans. In similar studies with P. aeruginosa, Pas did not mediate the biofilm formation with either the acute isolate (PAO1) or the chronic isolate (FRD1). However, the sortase A-deficient mutant (ΔsrtA) displayed reduced biofilm formation with both C. albicans and P. aeruginosa FRD1. Taken together, our findings highlight the role of Pas in both microbial-host and interkingdom interactions and expose its potential role in disease outcomes. IMPORTANCE Streptococcus intermedius, an oral commensal bacterium, has been clinically observed in subgingival dental plaque, purulent infections, and cystic fibrosis lungs. In this study, we have (i) determined the crystal structure of the V and C regions of Pas; (ii) shown that its surface protein Pas adheres to fibrinogen, which could potentially ferry the microbe through the bloodstream from the oral cavity; (iii) characterized Pas's high-affinity adherence to lung alveolar protein Gp340 that could fixate the microbe on lung epithelial cells; and (iv) most importantly, shown that these surface proteins on the oral commensal S. intermedius enhance biofilms of known pathogens Candida albicans and Pseudomonas aeruginosa.

Dataset Information

Positive- and Negative-Control Pathways by Blood Components for Intermedilysin Production in Streptococcus intermedius.

Publications

Positive- and Negative-Control Pathways by Blood Components for Intermedilysin Production in Streptococcus intermedius.

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