Hesperidin inhibits biofilm formation, virulence and staphyloxanthin synthesis in methicillin resistant Staphylococcus aureus by targeting SarA and CrtM: an in vitro and in silico approach

An updated and comprehensive review of the health benefits and pharmacological activities of hesperidin

OBJECTIVES

This review aims to comprehensively assess the health benefits and pharmacological activities of hesperidin, a flavonoid commonly found in citrus fruits. It consolidates recent research findings to provide insights into hesperidin's diverse health-promoting effects.

KEY FINDINGS

Hesperidin has gained significant attention recently for its notable pharmacological activities and potential health benefits. Studies reveal its antioxidant properties, protecting cells from oxidative damage, and its anti-inflammatory effects, inhibiting pro-inflammatory cytokines and enzymes. Also, hesperidin shows promise in cardiovascular health by reducing blood pressure and cholesterol levels and enhancing endothelial function. It also exhibits anticancer potential by hindering cell proliferation, inducing apoptosis, and suppressing tumour growth. Moreover, hesperidin demonstrates neuroprotective effects, potentially mitigating neuroinflammation and oxidative stress associated with neurodegenerative diseases. Furthermore, it displays beneficial effects in metabolic disorders such as diabetes, obesity, and fatty liver disease by influencing glucose metabolism, lipid profile, and insulin sensitivity.

SUMMARY

Hesperidin exhibits a wide range of health benefits and pharmacological activities, making it a promising candidate for therapeutic interventions in various diseases. Its antioxidant, anti-inflammatory, cardiovascular, anticancer, neuroprotective, and metabolic effects underscore its potential as a valuable natural compound for promoting health and preventing chronic diseases.

A novel volatile staphyloxanthin biosynthesis inhibitor against Staphylococcus aureus

In the present research, volatile organic compounds (VOCs) of garlic/mustard oil macerate (GMM) (garlic clove and mustard oil in the ratio of 1:4, heated at 80 OC for 4 h) were found to enhance the antibacterial activity of antibiotics (gentamycin, 41.17 %; kanamycin, 38.89 %, and streptomycin, 43.75 %) against S. aureus. The mechanism behind the enhancement of S. aureus's sensitivity to antibiotics may be due to the reduction of antibiotic resistance. On evaluating one of the well-known antibiotic resistance mechanisms of S. aureus, the ability to produce staphyloxanthin, it has been observed that the VOCs of GMM alone can decrease staphyloxanthin (44.23 ± 0.14 %) production. This decrease in staphyloxanthin production thereby increasing sensitivity to antibiotics, may be assigned to the compounds present in the VOCs of GMM. The major VOCs present in the GMM were identified as allicin, ajoene, vinyl dithiin, allyl isothiocyanate (AITC) and sinigrin. The order of binding of VOCs with dehydroxysqualene synthase (crtM) protein, which is important in staphyloxanthin production of S. aureus, was found to be sinigrin > ajoene > allicin > dithiin > AITC. Further, a decrease in staphyloxanthin production was found to increase the membrane fluidity of S. aureus as validated by Fourier-transformed infrared spectroscopy and scanning electron microscopy and this may allow antibiotics to enter inside the bacterial cell more rapidly. Thus, our research indicates that the VOCs in GMM may serve as a potential adjuvant when treating S. aureus infection.

Povidone-Iodine and Hydrogen Peroxide Combination Improves the Anti-Biofilm Activity of the Individual Agents on Staphylococcus aureus

Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA), poses significant challenges in healthcare settings due to its ability to form biofilms on various surfaces. These biofilms enhance bacterial survival and increase resistance to conventional treatments, complicating infection control efforts. This study evaluated the efficacy of combined povidone-iodine (PVP-I) and hydrogen peroxide (H2O2) to disrupt pre-formed S. aureus biofilms. A series of assays-including crystal violet staining, colony-forming unit (CFU) enumeration, gene expression analysis, and confocal laser scanning microscopy-were performed to assess the effects of each treatment individually and in combination. The combined treatment resulted in significantly greater reductions in biofilm biomass and viable bacteria compared with either agent alone. Gene expression analysis revealed downregulation of key biofilm-associated genes (icaA, icaB, icaD, icaR, and clfA), suggesting interference with biofilm stability and maintenance. While formal synergy quantification was not conducted, the observed effects suggest a potentially synergistic or additive interaction between the two agents. These findings support the use of dual antiseptic strategies as a promising approach to biofilm eradication and highlight the potential clinical utility of dual antiseptic strategies. However, we underscore the need for further optimization and safety evaluation.

Geranium essential oil downregulates virulence genes and mitigates MRSA wound infections through a multifunctional hydrogel

This study presents the development of a multifunctional hydrogel system that incorporates a natural therapeutic agent to promote wound healing and combat bacterial infections. A geranium essential oil (GEO)-loaded carboxymethyl chitosan-pullulan (CMCS-PLN-GEO) hydrogel was formulated for the treatment of MRSA-infected wounds. GEO exhibited potent antibiofilm and antivirulence properties by significantly downregulating key virulence-associated genes such as sarA, agrA, icaA, icaD, and clfA, indicating its potential as an effective therapeutic agent against MRSA. Integration of GEO into the CMCS-PLN hydrogel matrix enhanced its mechanical strength, reduced pore size, and enabled sustained GEO release. In a zebrafish wound model, the CMCS-PLN-GEO hydrogel markedly accelerated wound closure and suppressed MRSA colonization. Furthermore, it demonstrated strong anti-inflammatory activity through the downregulation of interleukin-1β (IL-1β), while promoting tissue regeneration via upregulation of transforming growth factor-β (TGF-β) and inhibition of matrix metalloproteinases MMP-9 and MMP-13. The synergistic integration of GEO with the CMCS-PLN polymer matrix offers dual antibacterial and anti-inflammatory effects, presenting a holistic therapeutic approach for the effective management of MRSA-infected wounds. The present study suggests that GEO-loaded hydrogel is a promising biomaterial for treating MRSA-infected wounds, potentially advancing toward clinical applications.

Investigating the bispecific lead compounds against methicillin-resistant Staphylococcus aureus SarA and CrtM using machine learning and molecular dynamics approach

Methicillin-resistant Staphylococcus aureus (MRSA) is a notorious pathogen that has emerged as a serious global health concern over the past few decades. Staphylococcal accessory regulator A (SarA) and 4,4'-diapophytoene synthase (CrtM) play a crucial role in biofilm formation and staphyloxanthin biosynthesis. Thus, the present study used a machine learning-based QSAR model to screen 1261 plant-derived natural organic compounds in order to identify a medication candidate with both biofilm and virulence inhibitory potential. Additionally, the in-silico molecular docking analysis has demonstrated significant binding efficacy of the identified hit compound, that is 85137543, with SarA and CrtM when compared to the control compound, hesperidin. Post-MD simulation analysis of the complexes depicted strong binding of 85137543 to both SarA and CrtM. Moreover, 85137543 showed hydrogen bonding with the key residues of both proteins during docking (ALA138 of SarA and ALA134 of CrtM) and post-MD simulation (LYS273 of CrtM and ASN212 of SarA). The RMSD of 85137543 was stable and consistent when bound to both CrtM and SarA with RMSDs of 1.3 and 1 nm, respectively. In addition, principal component analysis and the free energy landscape showed stable complex formation with both proteins. Low binding free energy (ΔGTotal) was observed by 85137543 for SarA (-47.92 kcal/mol) and CrtM (-36.43 kcal/mol), which showed strong binding. Overall, this study identified 85137543 as a potential inhibitor of both SarA and CrtM in MRSA.

Citrus flavonoids diosmin, myricetin and neohesperidin as inhibitors of Pseudomonas aeruginosa: Evidence from antibiofilm, gene expression and in vivo analysis

Citrus flavonoids are group of bioactive polyphenols. Here, we investigated the potential of diosmin, myricetin and neohesperidin as possible inhibitors of Pseudomonas aeruginosa. This bacterium is a major clinical challenge due to its propensity to form resistant biofilm. The aims of this study were to examine flavonoids antibacterial activity using the microdilution method, assays intended to determine several antibiofilm mechanisms (crystal violet, congo red binding, extracellular DNA (eDNA) test and confocal laser scanning microscopy (CLSM) live/dead cell imaging), followed by virulence genes RT-qPCR analysis. Furthermore, we aimed to examine in vivo toxicity of the compounds as well as their efficacy in P. aeruginosa zebrafish embryo infection model. Minimal inhibitory concentrations of tested flavonoids towards P. aeruginosa were in range 0.05 - 0.4 mg/mL. A high potential of the compounds to disturb both the formation of the bacterial biofilm and its eradication was recorded, including significant reduction in biofilm biomass, exopolysaccharide and eDNA production. Biofilm treatment with diosmin resulted in the lowest percentage of live microbial cells as observed in the CLSM live/dead cell imaging. The lasI, pvdS, and rhlC genes were found to be downregulated in the presence of diosmin and myricetin. Only diosmin stood out as non-embryotoxic. Consequently, in vivo analysis using a zebrafish model of P. aeruginosa infection showed an antivirulence effect of diosmin. Our findings suggest that diosmin could be potential candidate for the development of new agent that target P. aeruginosa infections by reducing its virulence mechanisms.

In silico testing to identify compounds that inhibit ClfA and ClfB binding to the host for the formulation of future drugs against Staphylococcus aureus colonization and infection

Introduction

Staphylococcus aureus is a highly resistant pathogen. It has multiple virulence factors, which makes it one of the most pathogenic bacteria for humankind. The vast increase in antibiotic resistance in these bacteria is a warning of existing healthcare policies. Most of the available antibiotics are ineffective due to resistance; this situation requires the development of drugs that target specific proteins and are not susceptible to resistance.

Methods

In this study, we identified a compound that acts as an antagonist of ClfA and ClfB by inhibiting their binding to host cells.

Results

The shortlisted compound's binding activity was tested by docking and molecular dynamics during its interaction with proteins. The identified compound has excellent binding energy with both ClfA (-10.11 kcal/mol) and ClfB (-11.11 kcal/mol).

Discussion

The molecular dynamics of the protein and compound were stable and promising for further in vitro and in vivo tests. The performance of our compound was tested and compared with that of the control molecule allantodapsone, which was reported in a previous study as a pan inhibitor of the clumping factor. An ADMET study of our selected compound revealed its reliable drug likeliness. This compound is an ideal candidate for in vitro studies.

Modified oxylipins as inhibitors of biofilm formation in Staphylococcus epidermidis

New approaches to combating microbial drug resistance are being sought, with the discovery of biofilm inhibitors considered as alternative arsenal for treating infections. Natural products have been at the forefront of antimicrobial discovery and serve as inspiration for the design of new antibiotics. We probed the potency, selectivity, and mechanism of anti-biofilm activity of modified oxylipins inspired by the marine natural product turneroic acid. Structure-activity relationship (SAR) evaluation revealed the importance of the trans-epoxide moiety, regardless of the position, for inhibiting biofilm formation. trans-12,13-epoxyoctadecanoic acid (1) and trans-9,10 epoxyoctadecanoic acid (4) selectively target the early stage of biofilm formation, with no effect on planktonic cells. These compounds interrupt the formation of a protective polysaccharide barrier by significantly upregulating the ica operon's transcriptional repressor. This was corroborated by docking experiment with SarA and scanning electron micrographs showing reduced biofilm aggregates and the absence of thread-like structures of extrapolymeric substances. In silico evaluation revealed that 1 and 4 can interfere with the AgrA-mediated communication language in Staphylococci, typical to the diffusible signal factor (DSF) capacity of lipophilic chains.

Effect of baicalin on eradicating biofilms of bovine milk derived Acinetobacter lwoffii

BACKGROUND

Acinetobacter lwoffii (A.lwoffii) is a serious zoonotic pathogen that has been identified as a cause of infections such as meningitis, bacteremia and pneumonia. In recent years, the infection rate and detection rate of A.lwoffii is increasing, especially in the breeding industry. Due to the presence of biofilms, it is difficult to eradicate and has become a potential super drug-resistant bacteria. Therefore, eradication of preformed biofilm is an alternative therapeutic action to control A.lwoffii infection. The present study aimed to clarify that baicalin could eradicate A.lwoffii biofilm in dairy cows, and to explore the mechanism of baicalin eradicating A.lwoffii.

RESULTS

The results showed that compared to the control group, the 4 MIC of baicalin significantly eradicated the preformed biofilm, and the effect was stable at this concentration, the number of viable bacteria in the biofilm was decreased by 0.67 Log10CFU/mL. The total fluorescence intensity of biofilm bacteria decreased significantly, with a reduction rate of 67.0%. There were 833 differentially expressed genes (367 up-regulated and 466 down-regulated), whose functions mainly focused on oxidative phosphorylation, biofilm regulation system and trehalose synthesis. Molecular docking analysis predicted 11 groups of target proteins that were well combined with baicalin, and the content of trehalose decreased significantly after the biofilm of A.lwoffii was treated with baicalin.

CONCLUSIONS

The present study evaluated the antibiofilm potential of baicalin against A.lwoffii. Baicalin revealed strong antibiofilm potential against A.lwoffii. Baicalin induced biofilm eradication may be related to oxidative phosphorylation and TCSs. Moreover, the decrease of trehalose content may be related to biofilm eradication.

Anti-virulence potential of patuletin, a natural flavone, against Staphylococcus aureus: In vitro and In silico investigations

Staphylococcus aureus is a highly prevalent and aggressive human pathogen causing a wide range of infections. This study aimed to explore the potential of Patuletin, a rare natural flavone, as an anti-virulence agent against S. aureus. At a sub-inhibitory concentration (1/4 MIC), Patuletin notably reduced biofilm formation by 27 % and 23 %, and decreased staphyloxanthin production by 53 % and 46 % in Staphylococcus aureus isolate SA25923 and clinical isolate SA1, respectively. In order to gain a more comprehensive understanding of the in vitro findings, several in silico analyses were conducted. Initially, a 3D-flexible alignment study demonstrated a favorable structural similarity between Patuletin and B70, the co-crystallized ligand of CrtM, an enzyme that plays a pivotal role in the biosynthesis of staphyloxanthin. Molecular docking highlighted the strong binding of Patuletin to the active site of CrtM, with a high affinity of -20.95 kcal/mol. Subsequent 200 ns molecular dynamics simulations, along with MM-GBSA, ProLIF, PLIP, and PCAT analyses, affirmed the stability of the Patuletin-CrtM complex, revealing no significant changes in CrtM's structure upon binding. Key amino acids crucial for binding were also identified. Collectively, this study showcased the effective inhibition of CrtM activity by Patuletin in silico and its attenuation of key virulence factors in vitro, including biofilm formation and staphyloxanthin production. These findings hint at Patuletin's potential as a valuable therapeutic agent, especially in combination with antibiotics, to counter antibiotic-resistant Staphylococcus aureus infections.

Potential of Flavonoids as Promising Phytotherapeutic Agents to Combat Multidrug-Resistant Infections

BACKGROUND

Considering the limited number of current effective treatments, Multidrug- Resistant (MDR) illnesses have grown to be a serious concern to public health. It has become necessary to look for new antimicrobial drugs because of the emergence of resistance to numerous kinds of antibiotics. The use of flavonoids is one phytotherapeutic strategy that has been researched as a potential remedy for this issue. Secondary plant compounds called flavonoids have been found to have an antibacterial effect against resistant microorganisms.

OBJECTIVE

This review seeks to give readers a glimpse into contemporary studies on flavonoids' potential to fight MDR infections.

METHODS

A systematic search was conducted on electronic databases (PubMed, Scopus, and Google Scholar) using relevant keywords such as flavonoids, MDR infections, antimicrobial activity, and resistance microbes. Studies that investigated the antimicrobial activity of flavonoids against resistant microbes were included in this review.

RESULTS

Most research found that flavonoids have antibacterial efficacy against resistant microorganisms, and some also showed that they have synergistic benefits with traditional antibiotics. The flavonoids quercetin, kaempferol, apigenin, and luteolin were the most often investigated ones. According to research, flavonoids affect microbial gene expression, inhibit microbial enzymes, and disrupt the integrity of microbial cell membranes. Additionally, a few studies have noted the flavonoids' low toxicity and safety.

CONCLUSION

For the treatment of infections that are resistant to many drugs, flavonoids constitute a promising class of phytotherapeutic agents. To develop flavonoid-based treatment methods for treating MDR illnesses and assess the potential of flavonoids as adjuvants to conventional antimicrobial drugs, more study is required.

The effect and mechanism of iodophors on the adhesion and virulence of Staphylococcus aureus biofilms attached to artificial joint materials

BACKGROUND

Iodophors are known to be a treatment for biofilm-related periprosthetic joint infection. However, the efficacy and mechanism of eradicating biofilms from different artificial joint materials after iodophor treatment are unknown. This study was conducted to understand the effect and mechanism of iodophors with respect to the adhesion and virulence of Staphylococcus aureus biofilms attached to artificial joint materials.

METHODS

Biofilms of Staphylococcus aureus strains were grown on titanium alloy, cobalt chromium molybdenum and polyethylene coupons, which are commonly used materials for artificial joints, for 24 h. Afterward, all coupons were divided into experimental and control groups: (1) exposed to a 0.5 ± 0.05% iodophor for 5 min and (2) exposed to phosphate-buffered saline for 5 min. To gauge the level of biofilm, colony forming units (CFU), live/dead staining confocal microscopy and crystal violet staining were used. Meanwhile, the expression of icaACDR and clfA, which are related to virulence and adhesion, was examined in both the experimental and control groups.

RESULTS

A roughly three-log decrease in CFU/cm2 was seen in the viable plate count compared to the control group. Confocal imaging and crystal violet staining verified the CFU data. Moreover, the expression of icaACDR was reduced on three different orthopaedic implant materials, and the expression of clfA was also inhibited on titanium alloy coupons exposed to the iodophor.

CONCLUSIONS

Our results indicated that exposure to an iodophor for 5 min could significantly eliminate biofilms. When Staphylococcus aureus that had adhered to these three materials, which were used for artificial joints, was treated with an iodophor for 5 min, the expression of icaACDR was significantly reduced. This provides strong evidence for clinically clearing periprosthetic joint infections without removing the artificial joints.

Development of Multifunctional Nanoencapsulated trans-Resveratrol/Chitosan Nutraceutical Edible Coating for Strawberry Preservation

Phytochemical nanoencapsulation for nutrient delivery and edible coatings for perishable food preservation are two emerging technologies. Leveraging the strong antimicrobial function of phytochemical nutrients, we propose convergent research to integrate the two technologies by embedding phytochemical-encapsulated nanoparticles in an edible coating on fresh fruits to achieve multiple functions. In particular, we report the study of an edible coating on strawberries that is composited of trans-resveratrol (R)-encapsulated nanoparticles (RNPs) embedded in a chitosan (CS) matrix. The biodegradable and biocompatible RNPs significantly increased the aqueous solubility of R by 150-fold and bioavailability by 3.5-fold after oral administration. Our results demonstrated the abilities of the RNP-embedded CS edible coating to diminish dehydration, prevent nutrient loss, inhibit microbe growth, increase nutraceutical value, preserve strawberry quality, and extend shelf life during storage at both 22 and 4 °C. Such a phytochemical nanoencapsulation-based edible coating is promising for the dual purposes of enhancing nutrient delivery and preserving perishable foods.

Diclofenac and Meloxicam Exhibited Anti-Virulence Activities Targeting Staphyloxanthin Production in Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a worldwide leading versatile pathogen that causes a wide range of serious infections. The emergence of antimicrobial resistance against S. aureus resulted in an urgent need to develop new antimicrobials in the new era. The methicillin-resistant S. aureus (MRSA) prevalence in hospital and community settings necessitates the discovery of novel anti-pathogenic agents. Staphyloxanthin (STX) is a key virulence factor for the survival of MRSA against host innate immunity. The current work aimed to demonstrate the anti-virulence properties of meloxicam (MXM) as compared to diclofenac (DC), which was previously reported to mitigate the virulence of multidrug-resistant Staphylococcus aureus and test their activities in STX production. A total of 80 S. aureus clinical isolates were included, wherein a qualitative and quantitative assessment of STX inhibition by diclofenac and meloxicam was performed. The quantitative gene expression of STX biosynthetic genes (crtM, crtN and sigB) and hla (coded for α-hemolysin) as a virulence gene with and without DC and MXM was conducted, followed by molecular docking analysis for further confirmation. DC and MXM potently inhibited the synthesis of STX at 47 and 59 µg/mL to reach 79.3-98% and 80.6-96.7% inhibition, respectively. Treated cells also revealed a significant downregulation of virulence genes responsible for STX synthesis, such as crtM, crtN and global transcriptional regulator sigB along with the hla gene. Furthermore, computational studies unveiled strong interactions between the CrtM binding site and DC/MXM. In conclusion, this study highlights the potential role and repurposing of DC and MXM as adjuvants to conventional antimicrobials and as an anti-virulent to combat MRSA infections.

Attenuating the virulence of the resistant superbug Staphylococcus aureus bacteria isolated from neonatal sepsis by ascorbic acid, dexamethasone, and sodium bicarbonate

Background

Infections affecting neonates caused by Staphylococcus aureus are widespread in healthcare facilities; hence, novel strategies are needed to fight this pathogen. In this study, we aimed to investigate the effectiveness of the FDA-approved medications ascorbic acid, dexamethasone, and sodium bicarbonate to reduce the virulence of the resistant Staphylococcus aureus bacteria that causes neonatal sepsis and seek out suitable alternatives to the problem of multi-drug resistance.

Methods

Tested drugs were assessed phenotypically and genotypically for their effects on virulence factors and virulence-encoding genes in Staphylococcus aureus. Furthermore, drugs were tested in vivo for their ability to reduce Staphylococcus aureus pathogenesis.

Results

Sub-inhibitory concentrations (1/8 MIC) of ascorbic acid, dexamethasone, and sodium bicarbonate reduced the production of Staphylococcus aureus virulence factors, including biofilm formation, staphyloxanthin, proteases, and hemolysin production, as well as resistance to oxidative stress. At the molecular level, qRT-PCR was used to assess the relative expression levels of crtM, sigB, sarA, agrA, hla, fnbA, and icaA genes regulating virulence factors production and showed a significant reduction in the relative expression levels of all the tested genes.

Conclusions

The current findings reveal that ascorbic acid, dexamethasone, and sodium bicarbonate have strong anti-virulence effects against Staphylococcus aureus. Thus, suggesting that they might be used as adjuvants to treat infections caused by Staphylococcus aureus in combination with conventional antimicrobials or as alternative therapies.

Eco-Friendly Solution Based on Rosmarinus officinalis Hydro-Alcoholic Extract to Prevent Biodeterioration of Cultural Heritage Objects and Buildings

Biodeterioration of cultural heritage is caused by different organisms capable of inducing complex alteration processes. The present study aimed to evaluate the efficiency of Rosmarinus officinalis hydro-alcoholic extract to inhibit the growth of deteriogenic microbial strains. For this, the physico-chemical characterization of the vegetal extract by UHPLC–MS/MS, its antimicrobial and antibiofilm activity on a representative number of biodeteriogenic microbial strains, as well as the antioxidant activity determined by DPPH, CUPRAC, FRAP, TEAC methods, were performed. The extract had a total phenol content of 15.62 ± 0.97 mg GAE/mL of which approximately 8.53% were flavonoids. The polyphenolic profile included carnosic acid, carnosol, rosmarinic acid and hesperidin as major components. The extract exhibited good and wide spectrum antimicrobial activity, with low MIC (minimal inhibitory concentration) values against fungal strains such as Aspergillus clavatus (MIC = 1.2 mg/mL) and bacterial strains such as Arthrobacter globiformis (MIC = 0.78 mg/mL) or Bacillus cereus (MIC = 1.56 mg/mL). The rosemary extract inhibited the adherence capacity to the inert substrate of Penicillium chrysogenum strains isolated from wooden objects or textiles and B. thuringiensis strains. A potential mechanism of R. officinalis antimicrobial activity could be represented by the release of nitric oxide (NO), a universal signalling molecule for stress management. Moreover, the treatment of microbial cultures with subinhibitory concentrations has modulated the production of microbial enzymes and organic acids involved in biodeterioration, with the effect depending on the studied microbial strain, isolation source and the tested soluble factor. This paper reports for the first time the potential of R. officinalis hydro-alcoholic extract for the development of eco-friendly solutions dedicated to the conservation/safeguarding of tangible cultural heritage.

Geraniol inhibits biofilm formation of methicillin-resistant Staphylococcus aureus and increase the therapeutic effect of vancomycin in vivo

Methicillin-resistant Staphylococcus aureus (MRSA) is among the common drug resistant bacteria, which has gained worldwide attention due to its high drug resistance and infection rates. Biofilms produced by S. aureus are known to increase antibiotic resistance, making the treatment of S. aureus infections even more challenging. Hence, inhibition of biofilm formation has become an alternative strategy for controlling persistent infections. In this study, we evaluated the efficacy of geraniol as a treatment for MRSA biofilm infection. The results of crystal violet staining indicated that 256 μg/mL concentration of geraniol inhibited USA300 biofilm formation by 86.13% and removed mature biofilms by 49.87%. Geraniol exerted its anti-biofilm effect by influencing the major components of the MRSA biofilm structure. We found that geraniol inhibited the synthesis of major virulence factors, including staphyloxanthin and autolysins. The colony count revealed that geraniol inhibited staphyloxanthin and sensitized USA300 cells to hydrogen peroxide. Interestingly, geraniol not only reduced the release of extracellular nucleic acids (eDNA) but also inhibited cell autolysis. Real-time polymerase chain reaction data revealed the downregulation of genes involved in biofilm formation, which verified the results of the phenotypic analysis. Geraniol increased the effect of vancomycin in eliminating USA300 biofilms in a mouse infection model. Our findings revealed that geraniol effectively inhibits biofilm formation in vitro. Furthermore, in combination with vancomycin, geraniol can reduce the biofilm adhesion to the implant in mice. This suggests the potential of geraniol as an anti-MRSA biofilm drug and can provide a solution for the clinical treatment of biofilm infection.

Staphyloxanthin as a Potential Novel Target for Deciphering Promising Anti-Staphylococcus aureus Agents

Staphylococcus aureus is a fatal Gram-positive pathogen threatening numerous cases of hospital-admitted patients worldwide. The emerging resistance of the pathogen to several antimicrobial agents has pressurized research to propose new strategies for combating antimicrobial resistance. Novel strategies include targeting the virulence factors of S. aureus. One of the most prominent virulence factors of S. aureus is its eponymous antioxidant pigment staphyloxanthin (STX), which is an auspicious target for anti-virulence therapy. This review provides an updated outline on STX and multiple strategies to attenuate this virulence factor. The approaches discussed in this article focus on bioprospective and chemically synthesized inhibitors of STX, inter-species communication and genetic manipulation. Various inhibitor molecules were found to exhibit appreciable inhibitory effect against STX and hence would be able to serve as potential anti-virulence agents for clinical use.