Oral streptococci subvert the host innate immune response through hydrogen peroxide.

In periodontal health, oral streptococci constitute up to 80% of the plaque biofilm. Yet, destructive inflammatory events of the periodontium are rare. This observation suggests that oral streptococci may possess mechanisms to co-exist with the host. However, the mechanisms employed by oral streptococci to modulate the innate immune response have not been well studied. One of the key virulence factors produced by oral streptococci is hydrogen peroxide (H2O2). In mammalian cells, H2O2 triggers the activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a key pathway mediating antioxidant defence. This study aimed to determine (1) if H2O2 producing oral streptococci activated the Nrf2 pathway in macrophages, and (2) if the activation of Nrf2 influenced the innate immune response. We found that oral streptococci downregulated the innate immune response in a H2O2 dependent manner through the activation of the Nrf2. The activation of the Nrf2 signalling pathway led to the inhibition of nuclear factor kappa-light-chain-enhancer of activated B cells (NFĸB), the key transcription factor regulating pro-inflammatory response. This study showed for the first time that oral streptococci are unlikely passive bystanders but could play an active role in the maintenance of periodontal health by preventing overt inflammation.

Fecal Streptococcus Alteration Is Associated with Gastric Cancer Occurrence and Liver Metastasis.

The gut microbiome plays an indispensable role in the occurrence and progression of various diseases. However, its ability to predict gastric cancer (GC) and liver metastasis (GCLM) has not been fully identified. Fecal samples were collected from 49 GC patients (cancer group [group C]) and 49 healthy people (normal group [group N]) between 4 July 2020 and 9 March 2021. Furthermore, 26 patients with metastatic GC were divided into a liver metastatic group (group L) (n = 13) and a non-liver-metastatic group (group M) (n = 13). DNA was extracted, and 16S rRNA gene sequencing was performed. SPSS was used for statistical analyses, and all bioinformatics analyses were based on QIIME2. P values of <0.05 were considered statistically significant. The microbial richness and diversity in group C were higher than those in group N, and there were significant differences in species compositions between the two groups. Streptococcus, enriched in groups C and L by linear discriminant analysis (LDA) effect size (LEfSe) and further identified by a random forest (RF) model, enhances its potential as a biomarker for GC and GCLM. Functional gene and metabolic pathway analyses showed that d-galacturonate degradation pathway II was of great importance in the occurrence and development of GC. Streptococcus has the potential ability to predict GC and GCLM, which is critical for the early diagnosis of GC and GCLM. IMPORTANCE The gut microbiome plays an indispensable role in the occurrence and progression of various diseases. However, its ability to predict gastric cancer (GC) and liver metastasis (GCLM) has not been fully identified. We retrospectively analyzed 49 untreated GC patients and 49 matched healthy people between 4 July 2020 and 9 March 2021. By extracting DNA from their fecal samples and sequencing the 16S rRNA gene, we found that Streptococcus alteration was strongly associated with GC occurrence and liver metastasis, which might be a potential biomarker in predicting GC and GCLM, and the results of this study are helpful in providing ideas for the early diagnosis and treatment of GC.

Proteins produced by Streptococcus species in the lower respiratory tract can modify antiviral responses against influenza virus in respiratory epithelial cells.

Seasonal influenza spreads during winter in temperate countries. Primary viral pneumoniae resulting from aggravation triggers acute respiratory distress syndrome, which is a serious respiratory disorder. We have identified a unique pattern of lung microbiota in patients with the syndrome. In this study, we hypothesized that the unique microbiota was also associated with primary influenza viral pneumoniae. Bacterial culture supernatants of Streptococcus oralis and Streptococcus mitis detected from the patients significantly increased viral replication (maximum 10-fold increase) in lung epithelial cells. Our results suggest that the lung environment microbiota is significantly involved in viral replication.

Cytotrophoblasts suppress macrophage-mediated inflammation through a contact-dependent mechanism.

PROBLEM: Gestational membrane (GM) infection provokes inflammation and can result in preterm prelabor rupture of membranes (PPROM). The choriodecidual layer of the GM includes decidual stromal cells (DSC), cytotrophoblasts (CTB), and macrophages (Mφ). Our laboratory has previously shown that DSCs suppress Mφ TNF-α production through secreted prostaglandin E2 . We hypothesized that CTBs would also inhibit Mφ cytokine expression through secreted mediators. METHOD OF STUDY: THP.1 Mφ-like cells with an NF-κB reporter construct or human blood monocyte-derived Mφ were co-cultured with the Jeg3 CTB cell line or primary human CTBs and challenged with group B streptococcus (GBS) or Toll-like receptor (TLR) agonists. Conditioned medium generated from CTB cultures was applied to Mφ cultures before infection or treatment. Alternatively, CTBs were co-incubated with, but physically separated from, Mφ and GBS or TLR-stimulated. NF-κB was assessed via alkaline phosphatase assay, and proinflammatory mediators were assessed by qRT-PCR and ELISA. RESULTS: CTBs suppressed GBS- or TLR-stimulated Mφ NF-κB activity, and TNF-α and MMP9 production. Direct physical contact between CTBs and Mφ was required for full immunosuppression. Immunosuppression could be overcome by increasing the ratio of Mφ to CTB. CONCLUSIONS: CTBs limit Mφ NF-κB activation and production of TNF-α and MMP9 through an as-yet unknown, cell-to-cell contact-mediated mechanism. This suppression is distinct from the PGE2 -mediated Mφ TNF-α suppression by DSC, suggesting that DSCs and CTBs regulate Mφ inflammation through distinct mechanisms. How Mφ integrates these signals in an intact GM will be paramount to determining causes and prevention of PPROM.

Repurposing Napabucasin as an Antimicrobial Agent against Oral Streptococcal Biofilms.

OBJECTIVES: Disruption of microbial biofilms is an effective way to control dental caries. Drug resistance and side effects of the existing antimicrobials necessitate the development of novel antibacterial agents. The current study was aimed at investigating the antibacterial activities of the repurposed natural compound napabucasin against oral streptococci. METHODS: The minimum inhibitory concentration, minimum bactericidal concentration, minimum biofilm inhibition concentration, and minimum biofilm reduction concentration of Streptococcus mutans, Streptococcus gordonii, and Streptococcus sanguinis were examined by a microdilution method. Cytotoxicity of napabucasin against human oral keratinocytes, human gingival epithelia, and macrophage RAW264.7 was evaluated by CCK8 assays. The dead/live bacterium and exopolysaccharide in the napabucasin-treated multispecies biofilms were evaluated by confocal laser scanning microscopy. Microbial composition within the napabucasin-treated biofilms was further visualized by fluorescent in situ hybridization and qPCR. And the cariogenicity of napabucasin-treated biofilms was evaluated by transverse microradiography. RESULTS: Napabucasin exhibited good antimicrobial activity against oral streptococcal planktonic cultures and biofilms but with lessened cytotoxicity as compared to chlorhexidine. Napabucasin reduced the cariogenic S. mutans and increased the proportion of the commensal S. gordonii in the multispecies biofilms. More importantly, napabucasin significantly reduced the demineralization capability of biofilms on tooth enamels. CONCLUSION: Napabucasin shows lessened cytotoxicity and comparable antimicrobial effects to chlorhexidine. Repurposing napabucasin may represent a promising adjuvant for the management of dental caries.

Calcium peroxide-mediated in situ formation of multifunctional hydrogels with enhanced mesenchymal stem cell behaviors and antibacterial properties.

Injectable hydrogels can serve as therapeutic vehicles and implants for the treatment of various diseases as well as for tissue repair/regeneration. In particular, the horseradish peroxidase (HRP) and hydrogen peroxide (H2O2)-catalyzed hydrogelation system has attracted much attention, due to its ease of handling and controllable gel properties. In this study, we introduce calcium peroxide (CaO2) as a H2O2-generating reagent to gradually supply a radical source for the HRP-catalyzed crosslinking reaction. This novel therapy can create stiff hydrogels without compromising the cytocompatibility of the hydrogels due to the use of initially high concentrations of H2O2. The physico-chemical properties of the hydrogels can be controlled by varying the concentrations of HRP and CaO2. In addition, the controlled and sustained release of bioactive molecules, including H2O2, O2, and Ca2+ ions, from the hydrogels could stimulate the cellular behaviors (attachment, migration, and differentiation) of human mesenchymal stem cells. Moreover, the hydrogels exhibited killing efficacy against both Gram-negative and Gram-positive bacteria, dependent on the H2O2 and Ca2+ release amounts. These positive results suggest that hydrogels formed by HRP/CaO2 can be used as potential matrices for a wide range of biomedical applications, such as bone regeneration and infection treatment.

Sulfated vizantin causes detachment of biofilms composed mainly of the genus Streptococcus without affecting bacterial growth and viability.

BACKGROUND: Sulfated vizantin, a recently developed immunostimulant, has also been found to exert antibiofilm properties. It acts not as a bactericide, but as a detachment-promoting agent by reducing the biofilm structural stability. This study aimed to investigate the mechanism underlying this activity and its species specificity using two distinct ex vivo oral biofilm models derived from human saliva. RESULTS: The biofilm, composed mainly of the genus Streptococcus and containing 50 µM of sulfated vizantin, detached significantly from its basal surface with rotation at 500 rpm for only 15 s, even when 0.2% sucrose was supplied. Expression analyses for genes associated with biofilm formation and bacterial adhesion following identification of the Streptococcus species, revealed that a variety of Streptococcus species in a cariogenic biofilm showed downregulation of genes encoding glucosyltransferases involved in the biosynthesis of water-soluble glucan. The expression of some genes encoding surface proteins was also downregulated. Of the two quorum sensing systems involved in the genus Streptococcus, the expression of luxS in three species, Streptococcus oralis, Streptococcus gordonii, and Streptococcus mutans, was significantly downregulated in the presence of 50 µM sulfated vizantin. Biofilm detachment may be facilitated by the reduced structural stability due to these modulations. As a non-specific reaction, 50 µM sulfated vizantin decreased cell surface hydrophobicity by binding to the cell surface, resulting in reduced bacterial adherence. CONCLUSION: Sulfated vizantin may be a candidate for a new antibiofilm strategy targeting the biofilm matrix while preserving the resident microflora.

Inflammatory Joint Disease Is a Risk Factor for Streptococcal Sepsis and Septic Arthritis in Mice.

Septic arthritis is a medical emergency associated with high morbidity and mortality, yet hardly any novel advances exist for its clinical management. Despite septic arthritis being a global health burden, experimental data uncovering its etiopathogenesis remain scarce. In particular, any interplay between septic arthritis and preceding joint diseases are unknown as is the contribution of the synovial membrane to the onset of inflammation. Using C57BL/6 mice as a model to study sepsis, we discovered that Group A Streptococcus (GAS) - an important pathogen causing septic arthritis - was able to invade the articular microenvironment. Bacterial invasion resulted in the infiltration of immune cells and detrimental inflammation. In vitro infected fibroblast-like synoviocytes induced the expression of chemokines (Ccl2, Cxcl2), inflammatory cytokines (Tnf, Il6), and integrin ligands (ICAM-1, VCAM-1). Apart from orchestrating immune cell attraction and retention, synoviocytes also upregulated mediators impacting on bone remodeling (Rankl) and cartilage integrity (Mmp13). Using collagen-induced arthritis in DBA/1 × B10.Q F1 mice, we could show that an inflammatory joint disease exacerbated subsequent septic arthritis which was associated with an excessive release of cytokines and eicosanoids. Importantly, the severity of joint inflammation controlled the extent of bone erosions during septic arthritis. In order to ameliorate septic arthritis, our results suggest that targeting synoviocytes might be a promising approach when treating patients with inflammatory joint disease for sepsis.

TLR13, TLR22, TRAF6, and TAK1 in the soiny mullet (Liza haematocheila): Molecular characterization and expression profiling analysis.

Toll-like receptors (TLRs) and their associated signaling pathways play pivotal roles in the immune response to invading pathogens. Here, TLR13, TLR22, tumor necrosis factor receptor-associated factor 6 (TRAF6), and transforming growth factor-ß-activated kinase1 (TAK1) were characterized in the soiny mullet (Liza haematocheila), representative mugilid species that is widely cultured in Asia. The four mullet genes, which shared characteristic features with their counterparts in other teleosts, were ubiquitously expressed in all of the examined tissues, albeit with different expression patterns. Following Streptococcus dysgalactiae infection, the four genes were upregulated to different degrees in various mullet tissues. These results indicated that the four genes were involved in the mullet immune response to bacterial infection. To the best of our knowledge, this is the first characterization of these four genes in mullet. Our results provide a basis for future studies of TLR signaling pathways in mullet, as well as for similar studies in other mugilids.

Relative expression of genes associated with adhesion to bovine mammary epithelial cells by Streptococcus uberis.

Streptococcus uberis is one of the most prevalent environmental pathogens of bovine mastitis. Biofilm growth ability by S. uberis looks to depend first upon the adherence of cells to a surface. The S. uberis ability to adhere to mammary gland epithelia might provide an advantage to colonize the lactating mammary gland. The objectives of this study were (a) to select S.uberis strains according to their ability to form biofilm, (b) to determine adherence to and internalization into MAC-T cells and (c) to investigate the expression profile adherence genes in these S. uberis strains. For the assays, the MAC-T bovine mammary epithelial cell line was used. Relative expression of genes acdA, lmb, scpA, sua, fbp and lbp was quantified by RT-qPCR. We observed that the RC38 strain from clinical bovine mastitis showed in the six genes higher values than control in both conditions. While the strain with greater ability to adhere, from clinical mastitis and biofilm producer (RC29) evidenced higher values in group 1 (G1) (bacteria after the initial contact with MAC-T cells) and decrease in group 2 (G2) (both adhered and internalized bacteria) than control. Strains with a moderate or strong capacity for biofilm production showed significantly lower relative expression values in the G2. In all adherence associated genes, strain RC19 showed relative expression values incremented in G1, while in G2 decreased expression. In conclusion, we did not find a single profile of relative expression because the relative expression levels of each gene differed depending on the strain and the co-culture stage of S. uberis cells from which RNA was obtained.

Flow path system of ultraviolet C irradiation from xenon flash to reduce bacteria survival in platelet products containing a platelet additive solution.

BACKGROUND: Our previous study showed that ultraviolet C (UVC) from xenon (Xe) flash without any photoreactive compounds inactivated bacteria in platelet concentrates (PCs) with less damage to platelets (PLTs) as compared with Xe flash containing ultraviolet A, ultraviolet B, and visible light. Here, we report a UVC irradiation system for PCs under flow conditions consisting of a flow path-irradiation sheet, a peristaltic pump, and a collection bag. STUDY DESIGN AND METHODS: Platelet concentrates containing Ringer's solution (R-PCs) inoculated with bacteria were injected into a flow path sheet using a peristaltic pump, being irradiated with UVC from Xe flash. The quality of the irradiated PCs containing platelet additive solution (PAS-PCs) was assessed based on PC variables, PLT surface markers, and aggregation ability. RESULTS: Streptococcus dysgalactiae (12 tests) and Escherichia coli (11) were all negative on bacterial culture, while Staphylococcus aureus (12) and Klebsiella pneumoniae (14) grew in one and two R-PCs, respectively. Bacillus cereus spores were inactivated in 7 of 12 R-PCs. PC variables became significantly different between irradiated and nonirradiated PAS-PCs. P-selectin, first procaspase-activating compound (PAC-1) binding, and phosphatidylserine increased by irradiation. Aggregability stimulated by adenosine diphosphate, collagen, or thromboxane A2 increased in the irradiated PAS-PCs, while that by thrombin became smaller compared with nonirradiated controls. CONCLUSION: This newly developed system inactivated bacteria including spores in R-PCs. PAS-PCs irradiated by this system retained acceptable in vitro quality and aggregability. Usage of a peristaltic pump instead of agitator during irradiation may enable this system to be directly combined with an apheresis blood cell separator.

Genomic and phenotypic assessments of safety and probiotic properties of Streptococcus macedonicus strains of dairy origin.

In this work, we studied the genomes and characterized some probiotic features of four S. macedonicus strains isolated from dairy environments in Italy that already had indicated some technological potential. The genomes of these strains were sequenced and used for genomic in silico studies. All strains were also evaluated for hemolytic activity, susceptibility to most commonly used antibiotics and probiotic potential, such as resistance to simulated gastrointestinal conditions, bile salts hydrolytic activity and adhesion ability to HT-29 human colorectal adenocarcinoma cells. Results revealed that one strain, namely S. macedonicus 211MA, was found to possess probiotic properties, such as resistance to simulated gastrointestinal conditions as well as adherence capability to human epithelial cells. In silico analyses revealed that S. macedonicus 211MA displayed the least number of single copy genes, genomic islands regions and gene content classified as virulence factors when compared to other S. macedonicus and S. gallolyticus strains. Moreover, the maximum gene content associated with bacterial stress response category and the presence of the opuCABCD operon, not detected in the other strains, were correlated with S. macedonicus 211MA capability to resist to low pH and to show higher adhesion to HT-29 human cells. This is the first report on the presence of opuCABCD operon in S. macedonicus and its possible relation with attachment ability and stress response.

Unsolved problems and new medical approaches to otitis media.

INTRODUCTION: Otitis media (OM) is a spectrum of infectious and inflammatory diseases that involve the middle ear. It includes acute otitis media (AOM), otitis media with effusion (OME) and chronic suppurative otitis media (CSOM). AREAS COVERED: This manuscript discusses some of the emerging and unsolved problems regarding OM, and some of the newly developed prophylactic and therapeutic medical measures. EXPERT OPINION: In recent years, considerable progress in the knowledge of OM physiopathology has been made. However, although extremely common, diseases included under OM have not been adequately studied, and many areas of development, evolution and possible treatments of these pathologies are not defined. It is necessary that these deficiencies be quickly overcome if we want to reduce the total burden of a group of diseases that still have extremely high medical, social and economic relevance.

Role of Toll-like receptor 2 against Streptococcus uberis infection in primary mouse mammary epithelial cells.

Mammary epithelial cells (MECs) play an important role against Streptococcus uberis infection which is one of the main causes of bovine mastitis and a potential threat to human health. Toll-like receptors (TLRs) and their mediated signaling pathways are critical in both innate and infection responses, yet their roles in anti-S. uberis infection in MECs remains poorly defined. In this work we investigated the regulatory mechanisms of TLR2 in inflammatory responses, where WT and TLR2-/- mice were euthanized at 15-18 days gestation, and mammary gland tissues were collected aseptically. The mouse MECs (MMECs) were isolated by combined digestion with type I collagenase, hyaluronidase and trypsin. We challenged MMECs with S. uberis and quantified antioxidant capacity as well as reactive oxygen species (ROS), proinflammatory cytokines and cell damage at different times. The loss of TLR2 function in MMECs results in more serious cell damage, increased cell adhesion, and significantly decreased ROS and mitochondrial ROS (mROS) with bactericidal function in response to S. uberis infection. Moreover, it was observed that the antioxidant capacity declined, and the production of TLR2-mediated cytokines (except CXC ligand 15) also were reduced. We demonstrated that TLR2 can mediate cellular anti-infective processes in MMECs by regulating the production of ROS and mROS and the secretion of cytokines. The results suggest an unpredicted role of TLR2 in MMECs in response to S. uberis infection.

Virulence of beta-hemolytic streptococci in infective endocarditis.

BACKGROUND: Streptococci involved in infective endocarditis (IE) primarily comprise alpha- or non-hemolytic streptococci (ANHS). Moreover, beta-hemolytic streptococci (BHS) can be involved, and guidelines recommend the addition of gentamicin for the first 2 weeks of treatment and the consideration of early surgery in such cases. This study compared the morbidity and mortality associated with IE depending on the microorganisms involved (BHS, ANHS, staphylococci, and enterococci). METHODS: We conducted a retrospective observational study between 2012 and 2017 in a single hospital in France. The endpoints were overall in-hospital mortality, 1-year mortality and the occurrence of complications. RESULTS: We analyzed 316 episodes of definite IE including 150 (38%), 96 (25%), 46 (12%), and 24 cases (6%) of staphylococcal, ANHS, enterococcal, and BHS IE, respectively. In-hospital mortality was significantly higher in the staphylococcal (n = 40; 26.7%) and BHS groups (n = 6; 25.0%) than in the ANHS (n = 9; 9.4%) and enterococcal groups (n = 5; 10.9%) (all p < 0.01). The rates of septic shock and cerebral emboli were also higher in the BHS group than in the ANHS group [n = 7 (29.2%) vs. n = 3 (3.1%), p < 0.001; n = 7 (29.2%) vs. n = 12 (12.5%); p = 0.05, respectively]. CONCLUSION: This study confirmed that BHS IE has a more severe prognosis than ANHS IE. The virulence of BHS may be similar to that of staphylococci, justifying increased monitoring of these patients and more 'aggressive' treatments such as early surgery.

The Pathogenic Factors from Oral Streptococci for Systemic Diseases.

The oral cavity is suggested as the reservoir of bacterial infection, and the oral and pharyngeal biofilms formed by oral bacterial flora, which is comprised of over 700 microbial species, have been found to be associated with systemic conditions. Almost all oral microorganisms are non-pathogenic opportunistic commensals to maintain oral health condition and defend against pathogenic microorganisms. However, oral Streptococci, the first microorganisms to colonize oral surfaces and the dominant microorganisms in the human mouth, has recently gained attention as the pathogens of various systemic diseases, such as infective endocarditis, purulent infections, brain hemorrhage, intestinal inflammation, and autoimmune diseases, as well as bacteremia. As pathogenic factors from oral Streptococci, extracellular polymeric substances, toxins, proteins and nucleic acids as well as vesicles, which secrete these components outside of bacterial cells in biofilm, have been reported. Therefore, it is necessary to consider that the relevance of these pathogenic factors to systemic diseases and also vaccine candidates to protect infectious diseases caused by Streptococci. This review article focuses on the mechanistic links among pathogenic factors from oral Streptococci, inflammation, and systemic diseases to provide the current understanding of oral biofilm infections based on biofilm and widespread systemic diseases.

Titanium alloys: in vitro biological analyzes on biofilm formation, biocompatibility, cell differentiation to induce bone formation, and immunological response.

Biological effects of titanium (Ti) alloys were analyzed on biofilms of Candida albicans, Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus mutans, and Streptococcus sanguinis, as well as on osteoblast-like cells (MG63) and murine macrophages (RAW 264.7). Standard samples composed of aluminum and vanadium (Ti-6Al-4V), and sample containing niobium (Ti-35Nb) and zirconium (Ti-13Nb-13Zr) were analyzed. Monomicrobial biofilms were formed on the Ti alloys. MG63 cells were grown with the alloys and the biocompatibility (MTT), total protein (TP) level, alkaline phosphatase (ALP) activity, and mineralization nodules (MN) formation were verified. Levels of interleukins (IL-1ß and IL-17), tumor necrosis factor alpha (TNF-α), and oxide nitric (NO) were checked, from RAW 264.7 cells supernatants. Data were statically analyzed by one-way analysis of variance (ANOVA) and Tukey's test, or T-test (P ≤ 0.05). Concerning the biofilm formation, Ti-13Nb-13Zr alloy showed the best inhibitory effect on E. faecalis, P. aeruginosa, and S. aureus. And, it also acted similarly to the Ti-6Al-4V alloy on C. albicans and Streptococcus spp. Both alloys were biocompatible and similar to the Ti-6Al-4V alloy. Additionally, Ti-13Nb-13Zr alloy was more effective for cell differentiation, as observed in the assays of ALP and MN. Regarding the stimulation for release of IL-1ß and TNF-α, Ti-35Nb and Ti-13Nb-13Zr alloys inhibited similarly the synthesis of these molecules. However, both alloys stimulated the production of IL-17. Additionally, all Ti alloys showed the same effect for NO generation. Thus, Ti-13Nb-13Zr alloy was the most effective for inhibition of biofilm formation, cell differentiation, and stimulation for release of immune mediators.

Streptococcus chosunense sp. nov., Isolated from Human Postoperative Maxillary Cyst.

A novel facultative anaerobic, non-spore forming, non-motile, and Gram-stain-positive coccus, designated strain ChDC B353T, was isolated from human postoperative maxillary cyst. The 16S ribosomal RNA gene (16S rDNA) sequence of the strain was most closely related to those of Streptococcus pseudopneumoniae ATCC BAA-960T (99.4%), Streptococcus mitis NCTC 12261T (99.3%), and Streptococcus pneumoniae NCTC 7465T (99.2%). The major fatty acids of the strain were C16:0 (43.2%) and C18:1 ω6c/C18:1 ω7c (20.2%). The genome of strain ChDC B353T was composed of 1,902,053 bps. The DNA G+C content of the strain was 40.2 mol%. Average nucleotide identity (ANI) values between strain ChDC B353T and S. pseudopneumoniae ATCC BAA-960T, S. mitis NCTC 12261T, and S. pneumoniae NCTC 7465T were 91.9%, 93.5%, and 91.3%, respectively. Genome-to-genome distance (GGD) values between strain ChDC B353T and S. pseudopneumoniae ATCC BAA-960T, S. mitis NCTC 12261T, or S. pneumoniae NCTC 7465T were 46.6% (44.0-49.2%), 53.2% (50.5-55.9%), and 46.0% (43.5-48.7%), respectively. The threshold values of ANI and GGD for species discrimination are 95-96% and 70%, respectively. These results reveal that strain ChDC B353T (= KCOM 1699T = JCM 33453T) is a novel species belonging to genus Streptococcus, for which a name of Streptococcus chosunense sp. nov. is proposed.

Differential expression of immune-related genes in head kidney and spleen of cobia (Rachycentron canadum) having Streptococcus dysgalactiae infection.

Streptococcus dysgalactiae is a gram-positive bacterium and a harmful aquaculture pathogen. To investigate the immune response against S. dysgalactiae, we performed transcriptome analysis of the head kidney and spleen of cobia (Rachycentron canadum) using RNA-seq. Total RNA was extracted from the head kidney and spleen of cobia, 1 and 2 days after treatment with S. dysgalactiae or control PBS. After RNA purification and cDNA library generation, sequencing was performed using the Illumina HiSeq™ 4000 platform. The filtering and de novo assembling transcripts were annotated using several databases. To identify differentially expressed genes (DEGs) between the S. dysgalactiae and PBS groups, the mapped values of fragments per kilobase of transcripts per million fragments were calculated. After de novo assembly, a total of 106,984 transcripts were detected, with an N50 of 3020 bp. These transcripts were annotated and categorised into a total of 7608 genes based on the KEGG pathway database. DEGs (2-fold difference) were calculated by comparing the S. dysgalactiae and PBS control group gene expression levels at each time point. The DEGs were mainly annotated into signal transduction and immune system categories, based on the KEGG database. The DEGs were significantly enriched in the immune-related pathways - "cytokine-cytokine receptor interaction", "complement and coagulation cascades", and "hematopoietic cell linage". In this study, immune-related genes responding to S. dysgalactiae were detected, and several immune system pathways were categorized. We identified the IL17C-related pathway for inducing the expression of pro-inflammatory cytokine genes (IL-1ß, IL-6, and IFNγ). Additionally, neutrophil-related genes (CSF3, CD121, and CD114) were induced in the spleen after S. dysgalactiae infection. It was suggested that these pathways contribute to immune responses against S. dysgalactiae infection. The data revealed in this study may offer improved strategies against S. dysgalactiae infection in cobia.

Streptococcus periodonticum sp. nov., Isolated from Human Subgingival Dental Plaque of Periodontitis Lesion.

A novel facultative anaerobic and Gram-stain-positive coccus, designated strain ChDC F135T, was isolated from human subgingival dental plaque of periodontitis lesion and was characterized by polyphasic taxonomic analysis. The 16S rRNA gene (16S rDNA) sequence of strain ChDC F135T was closest to that of Streptococcus sinensis HKU4T (98.2%), followed by Streptococcus intermedia SK54T (97.0%), Streptococcus constellatus NCTC11325T (96.0%), and Streptococcus anginosus NCTC 10713T (95.7%). In contrast, phylogenetic analysis based on the superoxide dismutase gene (sodA) and the RNA polymerase beta-subunit gene (rpoB) showed that the nucleotide sequence similarities of strain ChDC F135T were highly similar to the corresponding genes of S. anginosus NCTC 10713T (99.2% and 97.6%, respectively), S. constellatus NCTC11325T (87.8% and 91.4%, respectively), and S. intermedia SK54T (85.8% and 91.2%, respectively) rather than those of S. sinensis HKU4T (80.5% and 82.6%). The complete genome of strain ChDC F135T consisted of 1,901,251 bp and the G+C content was 38.9 mol %. Average nucleotide identity value between strain ChDC F135T and S. sinensis HKU4T or S. anginosus NCTC 10713T were 75.7% and 95.6%, respectively. The C14:0 composition of the cellular fatty acids of strain ChDC F135T (32.8%) was different from that of S. intermedia (6-8%), S. constellatus (6-13%), and S. anginosus (13-20%). Based on the results of phylogenetic and phenotypic analysis, strain ChDC F135T (= KCOM 2412T = JCM 33300T) was classified as a type strain of a novel species of the genus Streptococcus, for which we proposed the name Streptococcus periodonticum sp. nov.