Diflunisal-loaded poly(propylene sulfide) nanoparticles decrease S. aureus-mediated bone destruction during osteomyelitis

A precise targeting of Staphylococcus aureus with phage RBP-decorated antibiotic-loaded nanoparticles

Resistant strains of Staphylococcus aureus, which have emerged due to the excessive and indiscriminate use of antibiotics, have become one of the most significant causes of hospital-acquired infections, highlighting the necessity for specific and effective alternative methods in combating them. Leveraging the therapeutic potential of bacteriophage receptor binding protein (RBP), which occurs unique and irreversible binding of its host, in recognizing bacteria renders them valuable components in the development of targeted nanoparticle-based drug delivery systems, and offers promising approach to combat antibiotic resistance. In this study, synthesis and characterization of rifampicin-loaded PLGA nanoparticle (RIF-NP) were conducted and for selective targeting of S. aureus, rGp144, the RBP derived from Bacteriophage K, was conjugated onto the surface of the synthesized RIF-NP (RIF144-NP). While RIF-NP initially exhibited approximately a zeta potential of -26 mV and a size of 250 nm, after the conjugation with rGp144 led to an increase in zeta potential to -11 mV and a size to 300 nm. FT-IR analysis after conjugation confirmed the presence of primary amide bands in the regions of 1650 cm-1 and 1550 cm-1. Furthermore, the nanoparticles exhibited an encapsulation efficiency of 35.26% and a drug loading capacity of 26.64%. When the antimicrobial activities were evaluated, it was observed that compared to free RIF, the nano systems reduced the MIC value by twofold for all S. aureus strains. Incorporating a targeting strategy based on phage RBP in decoration to the surface of nanoparticular drug carriers represents a noteworthy and innovative treatment when combating bacterial infections.

Diflunisal attenuates acute inflammatory responses through inhibition of NF-κB signaling pathway in Staphylococcus aureus-induced mastitis of lactating mouse model

The cure rate of Staphylococcus aureus mastitis by conventional antibiotic therapy is very poor. Diflunisal (DIF), a difluorophenol derivative of salicylic acid, is reported to have strong anti-bacterial and anti-inflammatory effects against S. aureus infection. The present study aimed to evaluate the potential therapeutic effect of DIF administration against S. aureus-induced mastitis in mouse model by assessing the bacterial load, inflammation and histopathological changes in mammary gland. Eighteen lactating Swiss albino mice were divided into four groups: uninfected control, S. aureus-induced mastitis model, antibiotic (ceftriaxone)-treatment and diflunisal (DIF)-treatment. In S. aureus-induced mastitis mice, markedly increased bacterial load, myeloperoxidase, NF-κB and nitric oxide (NO) levels and up regulations of IL-1β, NF-κB and TNF-α mRNA expressions in mammary tissues with severe necrosis, marked infiltration of neutrophils and fibrosis in histopathology were noticed. Intramammary administration of DIF in S. aureus-induced mastitis mice showed a significant reduction in bacterial load, myeloperoxidase, NF-κB and NO concentrations in mammary tissues. The DIF treatment also suppressed the inflammatory NF-κB signaling in the inflamed mammary tissues by downregulation of IL-1β, NF-κB and TNF-α mRNA expressions. Further, the histopathology of mammary tissues showed mild necrosis with mild inflammatory cells infiltration, few bacterial colonies, moderate fibrosis, and marked regenerative changes with near to normal histological architecture. The findings of the study provide the evidence of therapeutic potential of DIF in S. aureus-induced mastitis by promising antibacterial and anti-inflammatory activities along with ameliorative impact against the histopathological alterations in mammary tissues.

STING-Pathway Inhibiting Nanoparticles (SPINs) as a Platform for Treatment of Inflammatory Diseases

Aberrant activation of the cyclic GMP-AMP synthase (cGAS)/Stimulator of Interferon Genes (STING) pathway has been implicated in the development and progression of a myriad of inflammatory diseases including colitis, nonalcoholic steatohepatitis, amyotrophic lateral sclerosis (ALS), and age-related macular degeneration. Thus, STING pathway inhibitors could have therapeutic application in many of these inflammatory conditions. The cGAS inhibitor RU.521 and the STING inhibitor H-151 have shown promise as therapeutics in mouse models of colitis, ALS, and more. However, these agents require frequent high-dose intraperitoneal injections, which may limit translatability. Furthermore, long-term use of systemically administered cGAS/STING inhibitors may leave patients vulnerable to viral infections and cancer. Thus, localized or targeted inhibition of the cGAS/STING pathway may be an attractive, broadly applicable treatment for a variety of STING pathway-driven ailments. Here we describe STING-Pathway Inhibiting Nanoparticles (SPINS)-poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with RU.521 and H-151-as a platform for enhanced and sustained inhibition of cGAS/STING signaling. We demonstrate that SPINs are equally or more effective at inhibiting type-I interferon responses induced by cytosolic DNA than free H-151 or RU.521. Additionally, we describe a SPIN formulation in which PLGA is coemulsified with poly(benzoyloxypropyl methacrylamide) (P(HPMA-Bz)), which significantly improves drug loading and allows for tunable release of H-151 over a period of days to over a week by varying P(HPMA-Bz) content. Finally, we find that all SPIN formulations were as potent or more potent in inhibiting cGAS/STING signaling in primary murine macrophages, resulting in decreased expression of inflammatory M1-like macrophage markers. Therefore, our study provides an in vitro proof-of-concept for nanoparticle delivery of STING pathway inhibitors and positions SPINs as a potential platform for slowing or reversing the onset or progression of cGAS/STING-driven inflammatory conditions.

Research Progress on Injectable Microspheres as New Strategies for the Treatment of Osteoarthritis Through Promotion of Cartilage Repair

Osteoarthritis (OA) is a degenerative disease caused by a variety of factors with joint pain as the main symptom, including fibrosis, chapping, ulcers, and loss of cartilage. Traditional treatment can only delay the progression of OA, and classical delivery system have many side effects. In recent years, microspheres have shown great application prospects in the field of OA treatment. Microspheres can support cells, reproduce the natural tissue microenvironment in vitro and in vivo, and are an efficient delivery system for the release of drugs or biological agents, which can promote cell proliferation, migration, and differentiation. Thus, they have been widely used in cartilage repair and regeneration. In this review, preparation processes, basic materials, and functional characteristics of various microspheres commonly used in OA treatment are systematically reviewed. Then it is introduced surface modification strategies that can improve the biological properties of microspheres and discussed a series of applications of microsphere functionalized scaffolds in OA treatment. Finally, based on bibliometrics research, the research development, future potential, and possible research hotspots of microspheres in the field of OA therapy is systematically and dynamically evaluated. The comprehensive and systematic review will bring new understanding to the field of microsphere treatment of OA.

Latest Advances in the Application of Humanized Mouse Model for Staphylococcus aureus

Staphylococcus aureus (S. aureus) is an important pathogen for humans and can cause a wide range of diseases, from mild skin infections, severe osteomyelitis to fatal pneumonia, sepsis, and septicemia. The mouse models have greatly facilitated the development of S. aureus studies. However, due to the substantial differences in immune system between mice and humans, the conventional mouse studies are not predictive of success in humans, in which case humanized mice may overcome this limitation to some extent. Humanized mice can be used to study the human-specific virulence factors produced by S. aureus and the mechanisms by which S. aureus interacts with humans. This review outlined the latest advances in humanized mouse models used in S. aureus studies.

Diflunisal and Analogue Pharmacophores Mediating Suppression of Virulence Phenotypes in Staphylococcus aureus

Invasive methicillin-resistant Staphylococcus aureus (MRSA) infections are leading causes of morbidity and mortality that are complicated by increasing resistance to conventional antibiotics. Thus, minimizing virulence and enhancing antibiotic efficacy against MRSA is a public health imperative. We originally demonstrated that diflunisal (DIF; [2-hydroxy-5-(2,4-difluorophenyl) benzoic acid]) inhibits S. aureus virulence factor expression. To investigate pharmacophores that are active in this function, we evaluated a library of structural analogues for their efficacy to modulate virulence phenotypes in a panel of clinically relevant S. aureus isolates in vitro. Overall, the positions of the phenyl, hydroxyl, and carboxylic moieties and the presence or type of halogen (F vs. Cl) influenced the efficacy of compounds in suppressing hemolysis, proteolysis, and biofilm virulence phenotypes. Analogues lacking halogens inhibited proteolysis to an extent similar to DIF but were ineffective at reducing hemolysis or biofilm production. In contrast, most analogues lacking the hydroxyl or carboxylic acid groups did not suppress proteolysis but did mitigate hemolysis and biofilm production to an extent similar to DIF. Interestingly, chirality and the substitution of fluorine with chlorine resulted in a differential reduction in virulence phenotypes. Together, this pattern of data suggests virulence-suppressing pharmacophores of DIF and structural analogues integrate halogen, hydroxyl, and carboxylic acid moiety stereochemistry. The anti-virulence effects of DIF were achieved using concentrations that are safe in humans, do not impair platelet antimicrobial functions, do not affect S. aureus growth, and do not alter the efficacy of conventional antibiotics. These results offer proof of concept for using novel anti-virulence strategies as adjuvants to antibiotic therapy to address the challenge of MRSA infection.

Stimulus-Responsive Drug Delivery Nanoplatforms for Osteoarthritis Therapy

Osteoarthritis (OA) is one of the most prevalent age-related degenerative diseases. With an increasingly aging global population, greater numbers of OA patients are providing clear economic and societal burdens. Surgical and pharmacological treatments are the most common and conventional therapeutic strategies for OA, but often fall considerably short of desired or optimal outcomes. With the development of stimulus-responsive nanoplatforms has come the potential for improved therapeutic strategies for OA. Enhanced control, longer retention time, higher loading rates, and increased sensitivity are among the potential benefits. This review summarizes the advanced application of stimulus-responsive drug delivery nanoplatforms for OA, categorized by either those that depend on endogenous stimulus (reactive oxygen species, pH, enzyme, and temperature), or those that depend on exogenous stimulus (near-infrared ray, ultrasound, magnetic fields). The opportunities, restrictions, and limitations related to these various drug delivery systems, or their combinations, are discussed in areas such as multi-functionality, image guidance, and multi-stimulus response. The remaining constraints and potential solutions that are represented by the clinical application of stimulus-responsive drug delivery nanoplatforms are finally summarized.

Diflunisal Attenuates Virulence Factor Gene Regulation and Phenotypes in Staphylococcus aureus

Virulence factor expression is integral to pathogenicity of Staphylococcus aureus. We previously demonstrated that aspirin, through its major metabolite, salicylic acid (SAL), modulates S. aureus virulence phenotypes in vitro and in vivo. We compared salicylate metabolites and a structural analogue for their ability to modulate S. aureus virulence factor expression and phenotypes: (i) acetylsalicylic acid (ASA, aspirin); (ii) ASA metabolites, salicylic acid (SAL), gentisic acid (GTA) and salicyluric acid (SUA); or (iii) diflunisal (DIF), a SAL structural analogue. None of these compounds altered the growth rate of any strain tested. ASA and its metabolites SAL, GTA and SUA moderately impaired hemolysis and proteolysis phenotypes in multiple S. aureus strain backgrounds and their respective deletion mutants. Only DIF significantly inhibited these virulence phenotypes in all strains. The kinetic profiles of ASA, SAL or DIF on expression of hla (alpha hemolysin), sspA (V8 protease) and their regulators (sigB, sarA, agr (RNAIII)) were assessed in two prototypic strain backgrounds: SH1000 (methicillin-sensitive S. aureus; MSSA) and LAC-USA300 (methicillin-resistant S. aureus; MRSA). DIF induced sigB expression which is coincident with the significant inhibition of RNAIII expression in both strains and precedes significant reductions in hla and sspA expression. The inhibited expression of these genes within 2 h resulted in the durable suppression of hemolysis and proteolysis phenotypes. These results indicate that DIF modulates the expression of key virulence factors in S. aureus via a coordinated impact on their relevant regulons and target effector genes. This strategy may hold opportunities to develop novel antivirulence strategies to address the ongoing challenge of antibiotic-resistant S. aureus.

Neutralization of Staphylococcus aureus Protein A Prevents Exacerbated Osteoclast Activity and Bone Loss during Osteomyelitis

Osteomyelitis caused by Staphylococcus aureus is an important and current health care problem worldwide. Treatment of this infection frequently fails not only due to the increasing incidence of antimicrobial-resistant isolates but also because of the ability of S. aureus to evade the immune system, adapt to the bone microenvironment, and persist within this tissue for decades. We have previously demonstrated the role of staphylococcal protein A (SpA) in the induction of exacerbated osteoclastogenesis and increased bone matrix degradation during osteomyelitis. The aim of this study was to evaluate the potential of using anti-SpA antibodies as an adjunctive therapy to control inflammation and bone damage. By using an experimental in vivo model of osteomyelitis, we demonstrated that the administration of an anti-SpA antibody by the intraperitoneal route prevented excessive inflammatory responses in the bone upon challenge with S. aureus. Ex vivo assays indicated that blocking SpA reduced the priming of osteoclast precursors and their response to RANKL. Moreover, the neutralization of SpA was able to prevent the differentiation and activation of osteoclasts in vivo, leading to reduced expression levels of cathepsin K, reduced expression of markers associated with abnormal bone formation, and decreased trabecular bone loss during osteomyelitis. Taken together, these results demonstrate the feasibility of using anti-SpA antibodies as an antivirulence adjunctive therapy that may prevent the development of pathological conditions that not only damage the bone but also favor bacterial escape from antimicrobials and the immune system.

Loss of Vhl alters trabecular bone loss during S. aureus osteomyelitis in a cell-specific manner

Osteomyelitis, or bone infection, is a major complication of accidental trauma or surgical procedures involving the musculoskeletal system. Staphylococcus aureus is the most frequently isolated pathogen in osteomyelitis and triggers significant bone loss. Hypoxia-inducible factor (HIF) signaling has been implicated in antibacterial immune responses as well as bone development and repair. In this study, the impact of bone cell HIF signaling on antibacterial responses and pathologic changes in bone architecture was explored using genetic models with knockout of either Hif1a or a negative regulator of HIF-1α, Vhl. Deletion of Hif1a in osteoblast-lineage cells via Osx-Cre (Hif1aΔOB ) had no impact on bacterial clearance or pathologic changes in bone architecture in a model of post-traumatic osteomyelitis. Knockout of Vhl in osteoblast-lineage cells via Osx-Cre (VhlΔOB ) caused expected increases in trabecular bone volume per total volume (BV/TV) at baseline and, intriguingly, did not exhibit an infection-mediated decline in trabecular BV/TV, unlike control mice. Despite this phenotype, bacterial burdens were not affected by loss of Vhl. In vitro studies demonstrated that transcriptional regulation of the osteoclastogenic cytokine receptor activator of NF-κB ligand (RANKL) and its inhibitor osteoprotegerin (OPG) is altered in osteoblast-lineage cells with knockout of Vhl. After observing no impact on bacterial clearance with osteoblast-lineage conditional knockouts, a LysM-Cre model was used to generate Hif1aΔMyeloid and VhlΔMyeloid mouse models to explore the impact of myeloid cell HIF signaling. In both Hif1aΔMyeloid and VhlΔMyeloid models, bacterial clearance was not impacted. Moreover, minimal impacts on bone architecture were observed. Thus, skeletal HIF signaling was not found to impact bacterial clearance in our mouse model of post-traumatic osteomyelitis, but Vhl deletion in the osteoblast lineage was found to limit infection-mediated trabecular bone loss, possibly via altered regulation of RANKL-OPG gene transcription.

The potential of oxygen and nitrogen species-regulating drug delivery systems in medicine

The focus of this review is to present most significant advances in biomaterials used for control of reactive oxygen/nitrogen species (ROS/RNS, RONS) in medicine. A summary of the main pathways of ROS production and the main pathways of RNS production are shown herein. Although the physiological and pathological roles of RONS have been known for at least 2decades, the potential of their control in management of disease went unappreciated. Recently, advances in the field of biochemical engineering and materials science have allowed for development of RONS-responsive biomaterials for biomedical applications, which aim to control and change levels of reactive species in tissue microenvironments. These materials utilize polymers, inorganic nanoparticles (NPs), or organic-inorganic hybrids. Thus, biomaterials like hydrogels have been developed to promote tissue regeneration by actively scavenging and reducing RONS levels. Their promising utility comes from thermo- and RONS-sensitivity, stability as a delivery-medium, ease for incorporation into other materials and facility for injection. Their particular attractiveness is attributed to drug release realized in targeted tissues and cells with elevated RONS levels, which leads to enhanced treatment outcomes and reduced adverse effects. The mechanism of their action depends on the functional groups employed and their response to oxidation, and may be based on solubility changes or cleavage of chemical bonds. When talking about antioxidants, one should also mention oxidative stress, which we call the imbalance between antioxidants and reactive oxygen species, which occurs due to a deficiency of endogenous antioxidants and a low supply of exogenous antioxidants. This study is a review of articles in English from the databases PubMed and Web of Science retrieved by applying the search terms “Oxygen Species, Nitrogen Species and biomaterials” from 1996 to 2021.

Insights on Development Aspects of Polymeric Nanocarriers: The Translation from Bench to Clinic

Scientists are focusing immense attention on polymeric nanocarriers as a prominent delivery vehicle for several biomedical applications including diagnosis of diseases, delivery of therapeutic agents, peptides, proteins, genes, siRNA, and vaccines due to their exciting physicochemical characteristics which circumvent degradation of unstable drugs, reduce toxic side effects through controlled release, and improve bioavailability. Polymers-based nanocarriers offer numerous benefits for in vivo drug delivery such as biocompatibility, biodegradability, non-immunogenicity, active drug targeting via surface modification, and controlled release due to their pH-and thermosensitive characteristics. Despite their potential for medicinal use, regulatory approval has been achieved for just a few. In this review, we discuss the historical development of polymers starting from their initial design to their evolution as nanocarriers for therapeutic delivery of drugs, peptides, and genes. The review article also expresses the applications of polymeric nanocarriers in the pharmaceutical and medical industry with a special emphasis on oral, ocular, parenteral, and topical application of drugs, peptides, and genes over the last two decades. The review further examines the practical, regulatory, and clinical considerations of the polymeric nanocarriers, their safety issues, and directinos for future research.

RC. Facile Synthesis of Epoxide-co-Propylene Sulphide Polymers with Compositional and Architectural Control

We present a facile method to produce propylene sulphide (PS) homopolymers up to 100 kg/mol and PS – epoxide statistical, block, and ABA copolymers using inexpensive and versatile thio-aluminium (SAl)...

Recent Advances in the Evaluation of Antimicrobial Materials for Resolution of Orthopedic Implant-Associated Infections In Vivo

While orthopedic implant-associated infections are rare, revision surgeries resulting from infections incur considerable healthcare costs and represent a substantial research area clinically, in academia, and in industry. In recent years, there have been numerous advances in the development of antimicrobial strategies for the prevention and treatment of orthopedic implant-associated infections which offer promise to improve the limitations of existing delivery systems through local and controlled release of antimicrobial agents. Prior to translation to in vivo orthopedic implant-associated infection models, the properties (e.g., degradation, antimicrobial activity, biocompatibility) of the antimicrobial materials can be evaluated in subcutaneous implant in vivo models. The antimicrobial materials are then incorporated into in vivo implant models to evaluate the efficacy of using the material to prevent or treat implant-associated infections. Recent technological advances such as 3D-printing, bacterial genomic sequencing, and real-time in vivo imaging of infection and inflammation have contributed to the development of preclinical implant-associated infection models that more effectively recapitulate the clinical presentation of infections and improve the evaluation of antimicrobial materials. This Review highlights the advantages and limitations of antimicrobial materials used in conjunction with orthopedic implants for the prevention and treatment of orthopedic implant-associated infections and discusses how these materials are evaluated in preclinical in vivo models. This analysis serves as a resource for biomaterial researchers in the selection of an appropriate orthopedic implant-associated infection preclinical model to evaluate novel antimicrobial materials.

Diflunisal Targeted Delivery Systems: A Review

Diflunisal is a well-known drug for the treatment of rheumatoid arthritis, osteoarthritis, primary dysmenorrhea, and colon cancer. This molecule belongs to the group of nonsteroidal anti-inflammatory drugs (NSAID) and thus possesses serious side effects such as cardiovascular diseases risk development, renal injury, and hepatic reactions. The last clinical data demonstrated that diflunisal is one of the recognized drugs for the treatment of cardiac amyloidosis and possesses a survival benefit similar to that of clinically approved tafamidis. Diflunisal stabilizes the transthyretin (TTR) tetramer and prevents the misfolding of monomers and dimers from forming amyloid deposits in the heart. To avoid serious side effects of diflunisal, the various delivery systems have been developed. In the present review, attention is given to the recent development of diflunisal-loaded delivery systems, its technology, release profiles, and effectiveness.

Shear stress and ROS-responsive biomimetic micelles for atherosclerosis via ROS consumption

Reactive oxygen species (ROS) are well-known important initiating factors required for atherosclerosis formation, which leads to endothelial dysfunction and plaque formation. Most of the existing antithrombotic therapies use ROS-responsive drug delivery systems, which have a certain therapeutic effect but cannot eliminate excess ROS. Therefore, the atherosclerosis cannot be treated from the source. Moreover, nanoparticles are easily cleared by the immune system during blood circulation, which is not conducive to long-term circulation. In this study, we developed an intelligent response system that could simultaneously respond to ROS and the shear stress microenvironment of atherosclerotic plaques. This system was formed by red blood cells (RBCs) and simvastatin-loaded micelles (SV MC). The micelles consisted of poly(glycidyl methacrylate)-polypropylene sulfide (PGED-PPS). The hydrophobic PPS could react with excess ROS to become hydrophilic, which forced the micelle rupture, resulting in drug release. Most importantly, PPS could also significantly deplete the ROS level, realizing the synergistic treatment of atherosclerosis with drugs and materials. The positively charged SV MC and negatively charged RBCs were self-assembled through electrostatic adsorption to obtain SV MC@RBCs. The SV MC@RBCs could respond to the high shear stress at the atherosclerotic plaque, and the shear stress induced SV MC desorption from the RBC surface. Using biomimetic methods to evade the SV MC@RBCs elimination by the immune system and to reduce the ROS plays a vital role in improving atherosclerosis treatment. The results of in vitro and in vivo experiments showed that SV MC@RBCs could effectively treat atherosclerosis. Moreover, not only does the SV MC@RBCs system avoid the risk of bleeding, but it also has excellent in vivo safety. The study results indicate that the SV MC@RBCs system is a promising therapeutic nanomedicine for treating ROS-related diseases.

Diflunisal-loaded poly(propylene sulfide) nanoparticles decrease S. aureus-mediated bone destruction during osteomyelitis

Osteomyelitis is a debilitating infection of bone that results in substantial morbidity. Staphylococcus aureus is the most commonly isolated pathogen causing bone infections and features an arsenal of virulence factors that contribute to bone destruction and counteract immune responses. We previously demonstrated that diflunisal, a nonsteroidal anti-inflammatory drug, decreases S. aureus-induced bone destruction during osteomyelitis when delivered locally from a resorbable drug delivery depot. However, local diflunisal therapy was complicated by bacterial colonization of the depot's surface, highlighting a common pitfall of devices for local drug delivery to infected tissue. It is, therefore, critical to develop an alternative drug delivery method for diflunisal to successfully repurpose this drug as an antivirulence therapy for osteomyelitis. We hypothesized that a nanoparticle-based parenteral delivery strategy would provide a method for delivering diflunisal to infected tissue while circumventing the complications associated with local delivery. In this study, we demonstrate that poly(propylene sulfide) (PPS) nanoparticles accumulate at the infectious focus in a murine model of staphylococcal osteomyelitis and are capable of efficaciously delivering diflunisal to infected bone. Moreover, diflunisal-loaded PPS nanoparticles effectively decrease S. aureus-mediated bone destruction, establishing the feasibility of systemic delivery of an antivirulence compound to mitigate bone pathology during osteomyelitis.

Antivirulence Strategies for the Treatment of Staphylococcus aureus Infections: A Mini Review

Staphylococcus aureus is a Gram-positive bacterium capable of infecting nearly all host tissues, causing severe morbidity and mortality. Widespread antimicrobial resistance has emerged among S. aureus clinical isolates, which are now the most frequent causes of nosocomial infection among drug-resistant pathogens. S. aureus produces an array of virulence factors that enhance in vivo fitness by liberating nutrients from the host or evading host immune responses. Staphylococcal virulence factors have been identified as viable therapeutic targets for treatment, as they contribute to disease pathogenesis, tissue injury, and treatment failure. Antivirulence strategies, or treatments targeting virulence without direct toxicity to the inciting pathogen, show promise as an adjunctive therapy to traditional antimicrobials. This Mini Review examines recent research on S. aureus antivirulence 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 categories: pore-forming toxins, immune evasion mechanisms, and the S. aureus quorum sensing system. These major areas of S. aureus antivirulence research demonstrate broad principles that may apply to other human pathogens. Finally, challenges of antivirulence research are outlined including the potential for resistance, the need to investigate multiple infection models, and the importance of studying antivirulence in conjunction with traditional antimicrobial treatments.