Additionally, it is important to recognize the natural occurrence ofagr-deficient isolates, for whichagrinhibition is inherently ineffective

Additionally, it is important to recognize the natural occurrence ofagr-deficient isolates, for whichagrinhibition is inherently ineffective. == Conclusion == Antivirulence strategies are actively under preclinical investigation as therapies for staphylococcal disease. traditional antimicrobials. This Mini Review examines recent research onS. aureusantivirulence strategies, with an emphasis on translational studies. While many different virulence factors have been investigated as therapeutic targets, this review focuses on strategies targeting three virulence groups: pore-forming toxins, immune evasion mechanisms, and theS. aureusquorum sensing system. These major areas ofS. aureusantivirulence research demonstrate broad principles that may apply to other human pathogens. Finally, difficulties of antivirulence research are outlined including the potential for resistance, the need to investigate multiple contamination models, and the importance of studying antivirulence in conjunction with traditional antimicrobial treatments. Keywords:Staphylococcus aureus bacteria, antivirulence, antimicrobial resistance, virulence, contamination, quorum sensing, accessory gene regulator, toxin == Introduction == Staphylococcus aureus, a Gram-positive bacterium, asymptomatically colonizes approximately 30% of the population and can infect nearly every tissue in the body (Wertheim et al., 2005;Monaco et al., 2017).S. aureusreadily adapts its metabolic and virulence responses in different tissues, causing superficial (e.g., folliculitis) and invasive infections (e.g., osteomyelitis;Balasubramanian et al., 2017;Potter et al., 2020).S. aureusbiofilm formation, toxin production, and immune evasion strategies limit host antibacterial immune responses (Thammavongsa et al., 2015a;Muthukrishnan et al., 2019). Therefore, staphylococcal infections often necessitate long-term antibiotics (Lew and Waldvogel, 2004;Hatzenbuehler and Pulling, 2011). However, common antimicrobial resistance has highlighted the need to develop additional treatments (Ventola, 2015). Staphylococcus aureusis the leading cause of nosocomial infections among antibiotic-resistant organisms, Rabbit Polyclonal to KCNK1 making staphylococcal infections a major target for investigation of antivirulence therapies (Sievert et al., 2013;Dickey et al., 2017). For the purposes of this review, antivirulence therapies are defined as those that do not inhibit bacterial growthin vitrobut limit the production or function of virulence factors that promote contamination or incite host damagein vivo. Antivirulence strategies aim to mitigate host tissue damage as host immune responses or standard antimicrobials eradicate contamination. The number of published studies on antivirulence techniques has increased dramatically over the last decade (Maura et al., 2016;Dickey et al., 2017). While most antivirulence strategies for staphylococcal disease are currently preclinical, several antibody-based antivirulence methods and one immunomodulatory peptide SU14813 (NCT02469857,ClinicalTrials.gov [Internet], 2015) are in clinical trials (Huynh et al., 2016;Levy et al., 2016;Franois et al., 2018,2019;Magyarics et al., 2019). This review will focus on recent investigations into antivirulence strategies targeting important virulence mechanisms ofS. aureusas layed out inFigure 1and outlined inTable 1. == FIGURE 1. == Staphylococcus aureusvirulence pathways and antivirulence strategies.(A)At top left, B-cells secrete antibodies SU14813 againstS. aureusantigens, the Fc region of which may be bound by Staphylococcal protein A (SpA) on theS. aureusmembrane, thereby subverting immune responses. SpA may also bind the Fab portion of VH3 family B-cell receptors, causing SpA-induced clonal growth and anergic collapse. Superantigen activity of SpA also influences antibody (Ab) production by narrowing the breadth of anti-staphylococcal antibodies from VH3 family B-cells, creating a preference for poorly functioning anti-SpA clones. To inhibit SpA activity, therapeutic monoclonal antibodies (mAbs) raised against an attenuated SpA have been delivered parenterally.(B)mAbs can also inhibit pore-forming toxins (PFTs). PFTs and phenol-soluble modulins (PSMs) are cytolytic toxins regulated by the accessory gene regulator (agr) quorum sensing system. To diminish these toxins cytotoxicity, decoy sponges limit the activity of the PFTs by presenting a variety of decoy receptors on their surfaces.(C)Neutrophils use reactive oxygen species (ROS) to kill phagocytosedS. aureus. These ROS are inhibited by staphyloxanthin, which in turn can be SU14813 inhibited by the drugs naftifine and NP16. At the image center, a schematic of theagrquorum sensing system is shown with color-coded protein labels. Beginning with transcription and translation of theagroperon, AgrB modifies and secretes AgrD to produce autoinducing peptide (AIP). Upon reaching quorum, AIP binds the receptor kinase, AgrC, which phosphorylates the response regulator, AgrA. AgrA activates the P2 and P3 promoters of theagroperon in a positive opinions loop and increases the production of many cytolytic virulence factors including PSMs and many PFTs. The Agr system may be targeted by several brokers including ambuic acid (inhibition of AIP secretion), solonamide B (inhibition of AIP activation of AgrC), and savirin and diflunisal (inhibition of AgrC and.