scholarly journals The accessory gene regulator-1 as a therapeutic target for C. difficile infections

2017 ◽  
Vol 21 (5) ◽  
pp. 451-453 ◽  
Author(s):  
Charles Darkoh ◽  
Herbert L. DuPont
Keyword(s):  
Therapeutic Target ◽  
Accessory Gene ◽  
Accessory Gene Regulator

scholarly journals Accessory Gene Regulator-1 Locus Is Essential for Virulence and Pathogenesis ofClostridium difficile

mBio ◽  
2016 ◽  
Vol 7 (4) ◽  
Author(s):  
Charles Darkoh ◽  
Chioma Odo ◽  
Herbert L. DuPont
Keyword(s):  
Health Care ◽  
Therapeutic Target ◽  
Treatment Options ◽  
Toxin Production ◽  
The United States ◽  
Multidrug Resistant ◽  
Accessory Gene ◽  
Ofclostridium Difficile ◽  
Accessory Gene Regulator ◽  
Toxin Regulation

ABSTRACTClostridium difficileinfection (CDI) is responsible for most of the definable cases of antibiotic- and hospital-associated diarrhea worldwide and is a frequent cause of morbidity and mortality in older patients.C. difficile, a multidrug-resistant anaerobic pathogen, causes disease by producing toxins A and B, which are controlled by an accessory gene regulator (Agr) quorum signaling system. SomeC. difficilestrains encode two Agr loci in their genomes, designatedagr1andagr2. Theagr1locus is present in all of theC. difficilestrains sequenced to date, whereas theagr2locus is present in a few strains. The functional roles ofagr1andagr2inC. difficiletoxin regulation and pathogenesis were unknown until now. Using allelic exchange, we deleted components of bothagrloci and examined the mutants for toxin production and virulence. The results showed that theagr1mutant cannot produce toxins A and B; toxin production can be restored by complementation with wild-typeagr1. Furthermore, theagr1mutant is able to colonize but unable to cause disease in a murine CDI model. These findings have profound implications for CDI treatment because we have uncovered a promising therapeutic target for the development of nonantibiotic drugs to treat this life-threatening emerging pathogen by targeting the toxins directly responsible for disease.IMPORTANCEWithin the last decade, the number of cases ofC. difficileinfections has been increasing exponentially in the United States, resulting in about 4.8 billion U.S. dollars in health care costs annually. As a multidrug-resistant, spore-forming, anaerobic pathogen,C. difficileoverpopulates the colon after the gut microbiota has been altered by antibiotic therapy. With increasing resistance to antibiotic treatment ofC. difficileinfections, patients are experiencing higher costs of health care and a lower quality of life as treatment options decrease. During infection,C. difficileproduces toxins A and B, which directly cause disease. As a result, the toxins have become promising nonantibiotic treatment targets. Here, we have identified a pathway responsible for activating the production of the toxins. This important finding opens up a unique therapeutic target for the development of a novel nonantibiotic therapy forC. difficileinfections.

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 Finding of Agr Phase Variants in Staphylococcus aureus

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Vishal Gor ◽  
Aya J. Takemura ◽  
Masami Nishitani ◽  
Masato Higashide ◽  
Veronica Medrano Romero ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Factors ◽  
Phase Variation ◽  
Accessory Gene ◽  
Content Type ◽  
Accessory Gene Regulator ◽  
Immune Mediated ◽  
A Minor ◽  
First Time ◽  
Phase Variants

ABSTRACT Staphylococcus aureus is an important human pathogen whose success is largely attributed to its vast arsenal of virulence factors that facilitate its invasion into, and survival within, the human host. The expression of these virulence factors is controlled by the quorum sensing accessory gene regulator (Agr) system. However, a large proportion of clinical S. aureus isolates are consistently found to have a mutationally inactivated Agr system. These mutants have a survival advantage in the host but are considered irreversible mutants. Here we show, for the first time, that a fraction of Agr-negative mutants can revert their Agr activity. By serially passaging Agr-negative strains and screening for phenotypic reversion of hemolysis and subsequent sequencing, we identified two mutational events responsible for reversion: a genetic duplication plus inversion event and a poly(A) tract alteration. Additionally, we demonstrate that one clinical Agr-negative methicillin-resistant S. aureus (MRSA) isolate could reproducibly generate Agr-revertant colonies with a poly(A) tract genetic mechanism. We also show that these revertants activate their Agr system upon phagocytosis. We propose a model in which a minor fraction of Agr-negative S. aureus strains are phase variants that can revert their Agr activity and may act as a cryptic insurance strategy against host-mediated stress. IMPORTANCE Staphylococcus aureus is responsible for a broad range of infections. This pathogen has a vast arsenal of virulence factors at its disposal, but avirulent strains are frequently isolated as the cause of clinical infections. These isolates have a mutated agr locus and have been believed to have no evolutionary future. Here we show that a fraction of Agr-negative strains can repair their mutated agr locus with mechanisms resembling phase variation. The agr revertants sustain an Agr OFF state as long as they exist as a minority but can activate their Agr system upon phagocytosis. These revertant cells might function as a cryptic insurance strategy to survive immune-mediated host stress that arises during infection.

scholarly journals Impact of agr Functionality on the Outcome of Patients with Methicillin-Susceptible Staphylococcus aureus Bacteremia

2021 ◽  
Author(s):  
Jeong Eun Lee ◽  
Shinwon Lee ◽  
Sohee Park ◽  
Soon O. Lee ◽  
Sun H. Lee
Keyword(s):  
Staphylococcus Aureus ◽  
Accessory Gene ◽  
Content Type ◽  
Accessory Gene Regulator ◽  
Staphylococcus Aureus Bacteremia ◽  
Mssa Infection

Few studies have examined the association between methicillin-susceptible Staphylococcus aureus (MSSA) infection and accessory gene regulator ( agr ) functionality. We evaluated the association between agr dysfunction and mortality in patients with MSSA bacteremia.

scholarly journals Evaluation of Accessory Gene Regulator (agr) Group and Function in the Proclivity towards Vancomycin Intermediate Resistance in Staphylococcus aureus

2006 ◽  
Vol 51 (3) ◽  
pp. 1089-1091 ◽  
Author(s):  
Brian T. Tsuji ◽  
Michael J. Rybak ◽  
Kerry L. Lau ◽  
George Sakoulas
Keyword(s):  
Staphylococcus Aureus ◽  
Wild Type ◽  
Accessory Gene ◽  
Time Curve ◽  
Unbound Fraction ◽  
Accessory Gene Regulator ◽  
Intermediate Resistance ◽  
And Function ◽  
Type Strains

ABSTRACT Simulated therapeutic vancomycin exposures were evaluated against agr wild-type and knockout Staphylococcus aureus groups I, II, III, and IV using an in vitro pharmacodynamic model. All agr groups developed intermediate resistance to vancomycin after subtherapeutic exposure. The free unbound fraction of the area under the concentration-time curve (fAUC/MIC) required to suppress resistance was fourfold higher (P < 0.001) in agr dysfunctional strains (112 to 169) than that in parent wild-type strains (28).

Regulation of toxic shock syndrome toxin‐1 by the accessory gene regulator in Staphylococcus aureus is mediated by the repressor of toxins

2019 ◽  
Vol 112 (4) ◽  
pp. 1163-1177 ◽  
Author(s):  
Stephen W. Tuffs ◽  
Christine A. Herfst ◽  
Miren L. Baroja ◽  
Vladyslav A. Podskalniy ◽  
Erica N. DeJong ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Toxic Shock Syndrome ◽  
Toxic Shock ◽  
Accessory Gene ◽  
Accessory Gene Regulator ◽  
Toxic Shock Syndrome Toxin

scholarly journals Construction and Characterization of anagr Deletion Mutant of Staphylococcus epidermidis

2000 ◽  
Vol 68 (3) ◽  
pp. 1048-1053 ◽  
Author(s):  
Cuong Vuong ◽  
Friedrich Götz ◽  
Michael Otto
Keyword(s):  
Staphylococcus Epidermidis ◽  
Deletion Mutant ◽  
Protein Pattern ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Surface Proteins ◽  
Accessory Gene ◽  
Accessory Gene Regulator ◽  
Sds Page ◽  
The Difference

ABSTRACT The physiological significance of the accessory gene regulator (agr) system of Staphylococcus epidermidis was investigated by construction of an agr deletion mutant via allelic replacement with a spectinomycin resistance cassette. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the protein pattern was strongly altered in the mutant; the amounts of most surface proteins were higher, whereas the amounts of most exoproteins were lower. The agrsystem of S. epidermidis thus appears to have an important impact on growth phase-dependent protein synthesis as has been shown for Staphylococcus aureus. The activity of the exoenzymes lipase and protease, assumed to be involved in staphylococcal pathogenicity, was investigated by agar diffusion assays and SDS-PAGE activity staining. A general reduction of these enzyme activities in the agr mutant was found. The difference in overall lipase activity was small, but zymographic analysis suggested a clear defect in lipase processing in the agr mutant.

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