Gram-positive bacteria secrete RNA aptamers to activate human STING for IL-1β release.

2021 ◽  
Author(s):  
Shivalee N Duduskar ◽  
Mohamed Ghait ◽  
Martin Westermann ◽  
Huijuan Guo ◽  
Anuradha Ramoji ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Rna Aptamers ◽  
Inflammasome Activation ◽  
Accessory Gene ◽  
Group B Streptococci ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Accessory Gene Regulator ◽  
New Perspective ◽  
Group B

Molecular mechanisms through which Gram-positive bacteria induce the canonical inflammasome are poorly understood. Here, we studied the effects of Group B streptococci (GBS) and Staphylococcus aureus (SA) on inflammasome activation in human macrophages. Dinucleotide binding small RNA aptamers released by SA and GBS were shown to trigger increased IL-1β generation by inflammasomes. The stimulator of interferon genes-STING as a central mediator of innate immune responses has been identified as the key target of pathogenic RNA. Multi-lamellar lipid bodies (MLBs) produced by SA function as vehicles for the RNA aptamers. Notably, expression of RNA aptamers is controlled by an accessory gene regulator quorum sensing system of the bacteria. These findings have been translated to patients with Gram-positive sepsis showing hallmarks of MLB-RNA-mediated inflammasome activation. Together our findings may provide a new perspective for the pathogenicity of Gram-positive bacterial infection in man.

scholarly journals In Vitro Activities of Two Ketolides, HMR 3647 and HMR 3004, against Gram-Positive Bacteria

1999 ◽  
Vol 43 (4) ◽  
pp. 930-936 ◽  
Author(s):  
Kumthorn Malathum ◽  
Teresa M. Coque ◽  
Kavindra V. Singh ◽  
Barbara E. Murray
Keyword(s):  
Dilution Method ◽  
Agar Dilution Method ◽  
Group A Streptococci ◽  
Group B Streptococci ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Streptococci Group B ◽  
Group A ◽  
Group B

ABSTRACT The in vitro activities of two new ketolides, HMR 3647 and HMR 3004, were tested by the agar dilution method against 280 strains of gram-positive bacteria with different antibiotic susceptibility profiles, including Staphylococcus aureus,Enterococcus faecalis, Enterococcus faecium,Streptococcus spp. (group A streptococci, group B streptococci, Streptococcus pneumoniae, and alpha-hemolytic streptococci). Seventeen erythromycin-susceptible (Ems), methicillin-susceptible S. aureus strains were found to have HMR 3647 and HMR 3004 MICs 4- to 16-fold lower than those of erythromycin (MIC at which 50% of isolates were inhibited [MIC50] [HMR 3647 and HMR 3004], 0.03 μg/ml; range, 0.03 to 0.06 μg/ml; MIC50 [erythromycin], 0.25 μg/ml; range, 0.25 to 0.5 μg/ml). All methicillin-resistant S. aureus strains tested were resistant to erythromycin and had HMR 3647 and HMR 3004 MICs of >64 μg/ml. The ketolides were slightly more active against E. faecalis than against E. faecium, and MICs for individual strains varied with erythromycin susceptibility. The MIC50s of HMR 3647 and HMR 3004 against Ems enterococci (MIC ≤ 0.5 μg/ml) and those enterococcal isolates with erythromycin MICs of 1 to 16 μg/ml were 0.015 μg/ml. E. faecalis strains that had erythromycin MICs of 128 to >512 μg/ml showed HMR 3647 MICs in the range of 0.03 to 16 μg/ml and HMR 3004 MICs in the range of 0.03 to 64 μg/ml. In the group of E. faecium strains for which MICs of erythromycin were ≥512 μg/ml, MICs of both ketolides were in the range of 1 to 64 μg/ml, with almost all isolates showing ketolide MICs of ≤16 μg/ml. The ketolides were also more active than erythromycin against group A streptococci, group B streptococci,S. pneumoniae, rhodococci, leuconostocs, pediococci, lactobacilli, and diphtheroids. Time-kill studies showed bactericidal activity against one strain of S. aureus among the four strains tested. The increased activity of ketolides against gram-positive bacteria suggests that further study of these agents for possible efficacy against infections caused by these bacteria is warranted.

scholarly journals Staphylococcus aureus CodY Negatively Regulates Virulence Gene Expression

2007 ◽  
Vol 190 (7) ◽  
pp. 2257-2265 ◽  
Author(s):  
Charlotte D. Majerczyk ◽  
Marat R. Sadykov ◽  
Thanh T. Luong ◽  
Chia Lee ◽  
Greg A. Somerville ◽  
...  
Keyword(s):  
Gene Expression ◽  
Staphylococcus Aureus ◽  
Regulatory Protein ◽  
Virulence Gene ◽  
Culture Fluid ◽  
Accessory Gene ◽  
Virulence Gene Expression ◽  
Gram Positive Bacteria ◽  
Accessory Gene Regulator ◽  
Branched Chain

ABSTRACT CodY is a global regulatory protein that was first discovered in Bacillus subtilis, where it couples gene expression to changes in the pools of critical metabolites through its activation by GTP and branched-chain amino acids. Homologs of CodY can be found encoded in the genomes of nearly all low-G+C gram-positive bacteria, including Staphylococcus aureus. The introduction of a codY-null mutation into two S. aureus clinical isolates, SA564 and UAMS-1, through allelic replacement, resulted in the overexpression of several virulence genes. The mutant strains had higher levels of hemolytic activity toward rabbit erythrocytes in their culture fluid, produced more polysaccharide intercellular adhesin (PIA), and formed more robust biofilms than did their isogenic parent strains. These phenotypes were associated with derepressed levels of RNA for the hemolytic alpha-toxin (hla), the accessory gene regulator (agr) (RNAII and RNAIII/hld), and the operon responsible for the production of PIA (icaADBC). These data suggest that CodY represses, either directly or indirectly, the synthesis of a number of virulence factors of S. aureus.

scholarly journals Anti-staphylococcal activity and mode of action of thioridazine photoproducts

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Tatiana Tozar ◽  
Sofia Santos Costa ◽  
Ana-Maria Udrea ◽  
Viorel Nastasa ◽  
Isabel Couto ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Molecular Docking ◽  
Infectious Diseases ◽  
Molecular Mechanisms ◽  
Dynamic Surface Tension ◽  
Docking Studies ◽  
Gram Positive ◽  
Dynamic Surface ◽  
Gram Positive Bacteria

Abstract Antibiotic resistance became an increasing risk for population health threatening our ability to fight infectious diseases. The objective of this study was to evaluate the activity of laser irradiated thioridazine (TZ) against clinically-relevant bacteria in view to fight antibiotic resistance. TZ in ultrapure water solutions was irradiated (1–240 min) with 266 nm pulsed laser radiation. Irradiated solutions were characterized by UV–Vis and FTIR absorption spectroscopy, thin layer chromatography, laser-induced fluorescence, and dynamic surface tension measurements. Molecular docking studies were made to evaluate the molecular mechanisms of photoproducts action against Staphylococcus aureus and MRSA. More general, solutions were evaluated for their antimicrobial and efflux inhibitory activity against a panel of bacteria of clinical relevance. We observed an enhanced antimicrobial activity of TZ photoproducts against Gram-positive bacteria. This was higher than ciprofloxacin effects for methicillin- and ciprofloxacin-resistant Staphylococcus aureus. Molecular docking showed the Penicillin-binding proteins PBP3 and PBP2a inhibition by sulforidazine as a possible mechanism of action against Staphylococcus aureus and MRSA strains, respectively. Irradiated TZ reveals possible advantages in the treatment of infectious diseases produced by antibiotic-resistant Gram-positive bacteria. TZ repurposing and its photoproducts, obtained by laser irradiation, show accelerated and low-costs of development if compared to chemical synthesis.

Target recognition, resistance, immunity and genome mining of class II bacteriocins from Gram-positive bacteria

Microbiology ◽  
2011 ◽  
Vol 157 (12) ◽  
pp. 3256-3267 ◽  
Author(s):  
Morten Kjos ◽  
Juan Borrero ◽  
Mona Opsata ◽  
Dagim J. Birri ◽  
Helge Holo ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Genome Mining ◽  
Class Ii ◽  
Biochemical Properties ◽  
Food Preservation ◽  
Target Cells ◽  
Detailed Knowledge ◽  
Genome Sequences ◽  
Gram Positive ◽  
Gram Positive Bacteria

Due to their very potent antimicrobial activity against diverse food-spoiling bacteria and pathogens and their favourable biochemical properties, peptide bacteriocins from Gram-positive bacteria have long been considered promising for applications in food preservation or medical treatment. To take advantage of bacteriocins in different applications, it is crucial to have detailed knowledge on the molecular mechanisms by which these peptides recognize and kill target cells, how producer cells protect themselves from their own bacteriocin (self-immunity) and how target cells may develop resistance. In this review we discuss some important recent progress in these areas for the non-lantibiotic (class II) bacteriocins. We also discuss some examples of how the current wealth of genome sequences provides an invaluable source in the search for novel class II bacteriocins.

scholarly journals Lipoteichoic Acid Is Important in Innate Immune Responses to Gram-Positive Bacteria

2007 ◽  
Vol 76 (1) ◽  
pp. 206-213 ◽  
Author(s):  
Ho Seong Seo ◽  
Suzanne M. Michalek ◽  
Moon H. Nahm
Keyword(s):  
Inflammatory Responses ◽  
Late Phase ◽  
Lipoteichoic Acid ◽  
Exponential Growth Phase ◽  
Group B Streptococci ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Positive Bacterial Culture ◽  
Tnf Α ◽  
Culture Supernatants

ABSTRACTTo define the role of lipoteichoic acid (LTA) in innate immunity to gram-positive bacteria, we investigated the production of tumor necrosis factor alpha (TNF-α) by macrophages stimulated with gram-positive bacterial culture supernatants (GPCSs) after their LTA was removed or inactivated. GPCSs were obtained from three gram-positive species (pneumococci, staphylococci, and group B streptococci) during the exponential growth phase (designated early GPCSs) or at the senescent stage (designated late GPCSs). LTA was removed using an anti-LTA antibody or was inactivated by alkaline hydrolysis or platelet-activating factor acetylhydrolase (PAF-AH) treatment. Both early and late GPCSs from the three gram-positive bacteria stimulated macrophages to produce TNF-α primarily via Toll-like receptor 2 (TLR2), although late pneumococcal supernatant could stimulate macrophages via TLR4 as well. Following LTA inactivation by both methods, early GPCS lost about 85 to 100% of its activity and late GPCS lost about 50 to 90%. Both early and late culture supernatants fromEscherichia colicould be inactivated by alkali hydrolysis but not by PAF-AH. In addition, removal of LTA from an early staphylococcal culture supernatant with a monoclonal antibody reduced about 70 to 85% of its potency. Reconstitution of inactivated early GPCS with a highly purified LTA restored its inflammatory activity, but the restored GPCS had higher activity than the pure LTA alone. These findings indicate that LTA is the primary TLR2 ligand in the early phase of gram-positive bacterial infection and remains a major ligand in the late phase when another TLR2 and TLR4 ligand(s) appears. In addition, our findings suggest that another gram-positive bacterial factor(s) synergizes with LTA in inducing inflammatory responses.

scholarly journals Toxin Synthesis by Clostridium difficile Is Regulated through Quorum Signaling

mBio ◽  
2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Charles Darkoh ◽  
Herbert L. DuPont ◽  
Steven J. Norris ◽  
Heidi B. Kaplan
Keyword(s):  
Clostridium Difficile ◽  
Gut Microbiota ◽  
Antibiotic Therapy ◽  
Molecular Mechanisms ◽  
Public Health Problem ◽  
The United States ◽  
Multidrug Resistant ◽  
Accessory Gene ◽  
Content Type ◽  
Accessory Gene Regulator

ABSTRACTClostridium difficileinfection (CDI) is dramatically increasing as a cause of antibiotic- and hospital-associated diarrhea worldwide. C. difficile, a multidrug-resistant pathogen, flourishes in the colon after the gut microbiota has been altered by antibiotic therapy. Consequently, it produces toxins A and B that directly cause disease. Despite the enormous public health problem posed by this pathogen, the molecular mechanisms that regulate production of the toxins, which are directly responsible for disease, remained largely unknown until now. Here, we show that C. difficile toxin synthesis is regulated by an accessory gene regulator quorum-signaling system, which is mediated through a small (<1,000-Da) thiolactone that can be detected directly in stools of CDI patients. These findings provide direct evidence of the mechanism of regulation of C. difficile toxin synthesis and offer exciting new avenues both for rapid detection of C. difficile infection and development of quorum-signaling-based non-antibiotic therapies to combat this life-threatening emerging pathogen.IMPORTANCEClostridium difficileinfection (CDI) is the most common definable cause of hospital-acquired and antibiotic-associated diarrhea in the United States, with the total cost of treatment estimated between 1 and 4.8 billion U.S. dollars annually. C. difficile, a Gram-positive, spore-forming anaerobe, flourishes in the colon after the gut microbiota has been altered by antibiotic therapy. As a result, there is an urgent need for non-antibiotic CDI treatments that preserve the colonic microbiota. C. difficile produces toxins A and B, which are directly responsible for disease. Here, we report that C. difficile regulates its toxin synthesis by quorum signaling, in which a novel signaling peptide activates transcription of the disease-causing toxin genes. This finding provides new therapeutic targets to be harnessed for novel nonantibiotic therapy for C. difficile infections.

scholarly journals Protein folding modulates the adhesion strategy of Gram positive pathogens

2019 ◽  
Author(s):  
Alvaro Alonso-Caballero ◽  
Daniel J. Echelman ◽  
Rafael Tapia-Rojo ◽  
Shubhasis Haldar ◽  
Edward C. Eckels ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Magnetic Tweezers ◽  
Gram Positive ◽  
Covalent Bonds ◽  
Surface Ligands ◽  
Gram Positive Bacteria ◽  
Mucosal Tissues ◽  
Mechanical Shocks ◽  
Thioester Bond ◽  
Amine Ligands

Gram positive bacteria colonize mucosal tissues against large mechanical perturbations, such as coughing, which generate large shear forces that exceed the ability of non-covalent bonds to remain attached. To overcome these challenges, the pathogen Streptococcus pyogenes utilizes the protein Cpa, a pilus tip-end adhesin equipped with a Cys-Gln thioester bond. The reactivity of this bond towards host surface ligands enables covalent anchoring of the bacterium, allowing it to resist large mechanical shocks; however, colonization also requires cell migration and spreading over surfaces. The molecular mechanisms underlying these seemingly incompatible requirements remain unknown. Here, we demonstrate a magnetic tweezers force spectroscopy assay that resolves the dynamics of Cpa thioester bond under force. While folded at forces < 6 pN, Cpa thioester bond reacts reversibly with amine ligands, of common occurrence in inflammation sites; however, mechanical unfolding and exposure to forces higher than 35 pN blocks thioester reactivity entirely. We propose that this folding-coupled thioester reactivity switch allows the adhesin to hop and sample host surface ligands at low force (nomadic mobility phase), and yet gets covalently anchored in place while under mechanical stress (locked phase). We dub such bonds “smart covalent bonds”, adding a novel class to the known repertoire of non-covalent adhesion strategies that include slip bonds, and catch bonds.

scholarly journals The Relevance of IL-1-Signaling in the Protection against Gram-Positive Bacteria

Pathogens ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 132
Author(s):  
Angelina Midiri ◽  
Giuseppe Mancuso ◽  
Concetta Beninati ◽  
Elisabetta Gerace ◽  
Carmelo Biondo
Keyword(s):  
Host Defense ◽  
Group A Streptococcus ◽  
Bacterial Species ◽  
Interleukin 1 ◽  
Group B Streptococcus ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Group A ◽  
Group B ◽  
Deficient Mice

Previous studies performed using a model of group B streptococcus (GBS)-induced peritoneal inflammation indicate that the interleukin-1 receptor (IL-1R) family plays an important role in the innate host defense against this encapsulated Gram-positive bacteria. Since the role of IL-1-dependent signaling in peritoneal infections induced by other Gram-positive bacteria is unknown, in the present study we sought to investigate the contribution of IL-1R signaling in host defenses against Streptococcus pyogenes (group A streptococcus or GAS) or Staphylococcus aureus, two frequent and global human Gram-positive extracellular pathogens. We analyzed here the outcome of GAS or S. aureus infection in IL-1R-deficient mice. After inoculated intraperitoneal (i.p.) inoculation with group A Streptococcus or S. aureus, all the wild-type (WT) control mice survived the challenge, while, respectively, 63% or 50% of IL-1-defective mice died. Lethality was due to the ability of both bacterial species to replicate and disseminate to the target organs of IL-1R-deficient mice. Moreover, the experimental results indicate that IL-1 signaling promotes the production of leukocyte attractant chemokines CXCL-1 and CXCL-2 and recruitment of neutrophils to bacterial infection sites. Accordingly, the reduced neutrophil recruitment in IL-1R-deficient mice was linked with decreased production of neutrophil chemokines. Collectively, our findings indicate that IL-1 signaling, as previously showed in host defense against GBS, plays a fundamental role also in controlling the progression and outcome of GAS or S. aureus disease.

scholarly journals Hemolytic Membrane Vesicles of Group B Streptococcus Promote Infection

2020 ◽  
Author(s):  
Blair Armistead ◽  
Phoenicia Quach ◽  
Jessica M Snyder ◽  
Verónica Santana-Ufret ◽  
Anna Furuta ◽  
...  
Keyword(s):  
Group B Streptococcus ◽  
Membrane Vesicles ◽  
Neonatal Infections ◽  
Group B Streptococci ◽  
Bacterial Surface ◽  
Gram Positive Bacteria ◽  
Bacterial Dissemination ◽  
Key Factor ◽  
Associated Proteins ◽  
Group B

Abstract Background Group B streptococci (GBS) are β-hemolytic, Gram-positive bacteria associated with fetal injury, preterm birth, spontaneous abortion, and neonatal infections. A key factor promoting GBS virulence is the β-hemolysin/cytolysin, a pigmented ornithine rhamnolipid (also known as granadaene) associated with the bacterial surface. Methods A previous study indicated that GBS produce small structures known as membrane vesicles (MVs), which contain virulence-associated proteins. In this study, we show that GBS MVs are pigmented and hemolytic, indicating that granadaene is functionally active in MVs. Results In addition, MVs from hyperhemolytic GBS induced greater cell death of neutrophils, T cells, and B cells compared with MVs from isogenic nonhemolytic GBS, implicating MVs as a potential mechanism for granadaene-mediated virulence. Finally, hemolytic MVs reduced oxidative killing of GBS and aggravated morbidity and mortality of neonatal mice infected with GBS. Conclusions These studies, taken together, reveal a novel mechanism by which GBS deploy a crucial virulence factor to promote bacterial dissemination and pathogenesis.

scholarly journals Human Milk Oligosaccharides Exhibit Biofilm Eradication Activity Against Matured Biofilms Formed by Different Pathogen Species

2022 ◽  
Vol 12 ◽  
Author(s):  
Sylwia Jarzynka ◽  
Riccardo Spott ◽  
Tinatini Tchatchiashvili ◽  
Nico Ueberschaar ◽  
Mark Grevsen Martinet ◽  
...  
Keyword(s):  
Human Milk ◽  
Pathogenic Bacteria ◽  
Biological Significance ◽  
Burkholderia Cenocepacia ◽  
Respiratory Pathogens ◽  
Human Milk Oligosaccharides ◽  
Group B Streptococci ◽  
Milk Oligosaccharides ◽  
Gram Positive ◽  
Group B

Human milk oligosaccharides (HMOs) have been shown to exhibit plenty of benefits for infants, such as prebiotic activity shaping the gut microbiota and immunomodulatory and anti-inflammatory activity. For some pathogenic bacteria, antimicrobial activity has been proved, but most studies focus on group B streptococci. In the present study, we investigated the antimicrobial and antibiofilm activities of the total and fractionated HMOs from pooled human milk against four common human pathogenic Gram-negative species (Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Burkholderia cenocepacia) and three Gram-positive species (Staphylococcus aureus, Enterococcus faecium, and Enterococcus faecalis). The activity of HMOs against enterococci and B. cenocepacia are addressed here for the first time. We showed that HMOs exhibit a predominant activity against the Gram-positive species, with E. faecalis being the most sensitive to the HMOs, both in planktonic bacteria and in biofilms. In further tests, we could exclude fucosyllactose as the antibacterial component. The biological significance of these findings may lie in the prevention of skin infections of the mother’s breast as a consequence of breastfeeding-induced skin laceration and/or protection of the infants’ nasopharynx and lung from respiratory pathogens such as staphylococci.

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