Quebrachitol inhibits biofilm formation and virulence production against methicillin-resistant Staphylococcus aureus

Disarming Staphylococcus aureus: Review of Strategies Combating This Resilient Pathogen by Targeting Its Virulence

Staphylococcus aureus is a formidable pathogen notorious for its antibiotic resistance and diverse virulence mechanisms, including toxin production, biofilm formation, and immune evasion. This article explores innovative anti-virulence strategies to disarm S. aureus by targeting critical virulence factors without exerting bactericidal pressure. Key approaches include inhibiting adhesion and biofilm formation, neutralizing toxins, disrupting quorum sensing (e.g., Agr system inhibitors), and blocking iron acquisition pathways. Additionally, interventions targeting two-component regulatory systems are highlighted. While promising, challenges such as strain variability, biofilm resilience, pharmacokinetic limitations, and resistance evolution underscore the need for combination therapies and advanced formulations. Integrating anti-virulence strategies with traditional antibiotics and host-directed therapies offers a sustainable solution to combat multidrug-resistant S. aureus, particularly methicillin-resistant strains (MRSA), and mitigate the global public health crisis.

Antibiofilm Activities of Multiple Halogenated Pyrimidines Against Staphylococcus aureus

Staphylococcus aureus, prevalent in hospital and community settings, forms biofilms that are highly resistant to antibiotics and immune responses, complicating treatment and contributing to chronic infections. These challenges underscore the need for novel treatments that target biofilm formation and effectively reduce bacterial virulence. This study investigates the antibiofilm and antimicrobial efficacy of novel halogenated pyrimidine derivatives against S. aureus, focusing on three compounds identified as potent biofilm inhibitors: 2,4-dichloro-5-fluoropyrimidine (24DC5FP), 5-bromo-2,4-dichloro-7H-pyrrolo[2,3-d]pyrimidine (24DC5BPP), and 2,4-dichloro-5-iodo-7H-pyrrolo[2,3-d]pyrimidine (24DC5IPP). The three active compounds are bacteriostatic. In particular, 24DC5FP at 5 µg/mL achieved a 95% reduction in hemolysis with a minimum inhibitory concentration (MIC) of 50 µg/mL. Interestingly, 24DC5FP increased cell size and produced wrinkled colonies. qRT-PCR analysis showed that 24DC5FP suppressed the gene expressions of agrA and RNAIII (quorum sensing regulator and effector), hla (α-hemolysin), nuc1 (nucleases nuc1), and saeR (S. aureus virulence regulator). These findings suggest that extensive halogenation enhances the antibiofilm and antivirulence activities of pyrimidine derivatives, offering a promising strategy for combatting S. aureus infections, including those resistant to conventional treatments.

Inhibition of Staphylococcus aureus biofilm by quercetin combined with antibiotics

This study aimed to investigate the effects of combined quercetin and antibiotics on the bacteriostatic activity and biofilm formation of Staphylococcus aureus. Optimal concentrations of quercetin and antibiotics (tetracycline and doxycycline) for inhibiting biofilm formation were determined using the Fractional Inhibitory Concentration Index and Minimum Biofilm Inhibitory Concentration assays. The impact of the drug combinations on biofilm clearance at various formation stages was determined using crystal violet staining, scanning electron microscopy and confocal laser microscopy. The results indicated that quercetin enhanced the bactericidal effect of tetracycline antibiotics against S. aureus. The combination significantly reduced both the metabolic activity within S. aureus biofilms and the production of biofilm matrix components. Scanning electron microscopy and confocal laser microscopy confirmed that the combination treatment significantly reduced bacterial cell counts within the biofilm. Quercetin treatment significantly increased the sensitivity of biofilms to antibiotics, supporting its potential application as a novel antibiotic synergist.

Transcriptomic Analysis of the Effect of Glabridin on Biofilm Formation in Staphylococcus Aureus

Staphylococcus aureus (S. aureus) is among the major skin infection-causing pathogens in animals and humans. Its ability to form biofilms has become a foremost cause of bacterial infections and the extensive spread of drug resistance, which poses a great difficulty in clinical treatment. Glabridin (Glb), an extract of licorice with antibacterial and anti-infective properties, has a partially understood biofilm-inhibitory mechanism. This study investigated the inhibitory and antibiofilm activities of subinhibitory concentrations of Glb against S. aureus. The crystal violet assay revealed that Glb significantly suppressed biofilm expression. Scanning electron microscopy observations unveiled that Glb reduced S. aureus adhesion and accumulation by disrupting the spatial structure of the biofilm. In vitro extracellular DNA (eDNA) inhibition assays demonstrated that Glb inhibited biofilm formation by S. aureus by suppressing eDNA secretion. In total, 184 differentially expressed genes were obtained through transcriptomic (RNA-seq) sequencing, of which 81 and 103 genes were upregulated and downregulated, respectively. Glb regulated the transcript levels of biofilm-related genes through the phosphatase transfer system, two-component regulatory system, and nitrogen metabolism. The qPCR analysis was performed to confirm whether Glb interfered with the expression of regulatory genes involved in S. aureus biofilm formation (SarA, ArlR, FnbA, ClfA, icaD, and icaR) as well as the virulence gene Hla. In conclusion, this study demonstrates that Glb has a significant inhibitory effect on biofilm activity and is expected to be a good antibiofilm drug.

Antimicrobial activities of lavandulylated flavonoids in Sophora flavences against methicillin-resistant Staphylococcus aureus via membrane disruption

INTRODUCTION

The continuous emergence and rapid spread of multidrug-resistant bacteria have accelerated the demand for the discovery of alternative antibiotics. Natural plants contain a variety of antibacterial components, which is an important source for the discovery of antimicrobial agents.

OBJECTIVE

To explore the antimicrobial activities and related mechanisms of two lavandulylated flavonoids, sophoraflavanone G and kurarinone in Sophora flavescens against methicillin-resistant Staphylococcus aureus.

METHODS

The effects of sophoraflavanone G and kurarinone on methicillin-resistant Staphylococcus aureus were comprehensively investigated by a combination of proteomics and metabolomics studies. Bacterial morphology was observed by scanning electron microscopy. Membrane fluidity, membrane potential, and membrane integrity were determined using the fluorescent probes Laurdan, DiSC3(5), and propidium iodide, respectively. Adenosine triphosphate and reactive oxygen species levels were determined using the adenosine triphosphate kit and reactive oxygen species kit, respectively. The affinity activity of sophoraflavanone G to the cell membrane was determined by isothermal titration calorimetry assays.

RESULTS

Sophoraflavanone G and kurarinone showed significant antibacterial activity and anti-multidrug resistance properties. Mechanistic studies mainly showed that they could target the bacterial membrane and cause the destruction of the membrane integrity and biosynthesis. They could inhibit cell wall synthesis, induce hydrolysis and prevent bacteria from synthesizing biofilms. In addition, they can interfere with the energy metabolism of methicillin-resistant Staphylococcus aureus and disrupt the normal physiological activities of the bacteria. In vivo studies have shown that they can significantly improve wound infection and promote wound healing.

CONCLUSION

Kurarinone and sophoraflavanone G showed promising antimicrobial properties against methicillin-resistant Staphylococcus aureus, suggesting that they may be potential candidates for the development of new antibiotic agents against multidrug-resistant bacteria.

Prodigiosin as an antibiofilm agent against multidrug-resistant Staphylococcus aureus

Staphylococcus aureus is known for forming bacterial biofilms that confer increased antimicrobial resistance. Combining antibiotics with antibiofilm agents is an alternative approach, but the antibiofilm ability of prodigiosin (PG), a potential antibiotic synergist, against antimicrobial-resistant (AMR) S. aureus remains to be understood. The antibiofilm activity of PG against 29 clinical AMR S. aureus strains was evaluated using crystal violet staining, and its synergistic effects with vancomycin (VAN) was confirmed using the checkerboard test. The viability and metabolic activity of biofilms and planktonic cells were also assessed. The results revealed that PG exhibited promising inhibitory activity against biofilm formation and synergistic activity with VAN. It effectively reduced the metabolic activity of biofilms and suppressed the production of exopolysaccharides, which might be attributed to the downregulation of biofilm-related genes such as sarA, agrA, and icaA. These findings suggest that PG could be used as a preventive coating or adjuvant against biofilms in clinical settings.

Synergistic Inhibitory Effect of Honey and Lactobacillus plantarum on Pathogenic Bacteria and Their Promotion of Healing in Infected Wounds

Prevention and control of infections have become a formidable challenge due to the increasing resistance of pathogens to antibiotics. Probiotics have been discovered to have positive effects on the host, and it is well-known that some Lactobacilli are effective in treating and preventing inflammatory and infectious diseases. In this study, we developed an antibacterial formulation consisting of honey and Lactobacillus plantarum (honey-L. plantarum). The optimal formulation of honey (10%) and L. plantarum (1 × 10⁹ CFU/mL) was used to investigate its antimicrobial effect and mechanism in vitro, and its healing effect on wound healing of whole skin infections in rats. Biofilm crystalline violet staining and fluorescent staining results indicated that the honey-L. plantarum formulation prevented the biofilm formation in Staphylococcus aureus and Pseudomonas aeruginosa and increased the number of dead bacteria in the biofilms. Further mechanism studies revealed that the honey-L. plantarum formulation may inhibit biofilm formation by upregulating biofilm-related genes (icaA, icaR, sigB, sarA, and agrA) and downregulating quorum sensing (QS) associated genes (lasI, lasR, rhlI, rhlR, and pqsR). Furthermore, the honey-L. plantarum formulation decreased the number of bacteria in the infected wounds of rats and accelerated the formation of new connective tissue to promote wound healing. Our study suggests that the honey-L. plantarum formulation provides a promising option for the treatment of pathogenic infections and wound healing.

Quorum sensing inhibitory potential of vaccenic acid against Chromobacterium violaceum and methicillin-resistant Staphylococcus aureus

Quorum sensing (QS) is a potential target for inhibiting bacterial antibiotic resistance and associated pathogenicity. The present study aimed to investigate vaccenic acid anti-QS and antibiofilm potential against Chromobacterium violaceum and methicillin-resistant Staphylococcus aureus (MRSA). In the broth microdilution method, we determined the minimum inhibitory concentration (MIC) of vaccenic acid against C. violaceum and MRSA. Then, we determined the vaccenic acid anti-QS potential against C. violaceum via a violacein inhibition assay. Vaccenic acid at a sub-MIC concentration significantly inhibited violacein pigment production. Vaccenic acid also inhibits C. violaceum and MRSA biofilm formation at sub-MIC concentrations. The effect of vaccenic acid antivirulence potential was evaluated by phenotypic virulence assays. The results showed that vaccenic acid at a sub-MIC concentration significantly inhibited the virulence production of C. violaceum (chitinase and motility) and MRSA (hemolysin and staphyloxanthin production). Quantitative PCR analysis revealed the downregulation of QS associated genes upon vaccenic acid treatment. This resulted in the downregulation of genes involved in QS mechanisms such as cviI, cviR, and SarA and pigment production such as vioB and crtM. The results of the present study suggest that vaccenic acid is a promising agent to combat C. violaceum and MRSA.

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

Methicillin resistant Staphylococcus aureus is considered multidrug resistant bacterium due to developing biofilm formation associated with antimicrobial resistance mechanisms. Therefore, inhibition of biofilm formation is an alternative therapeutic action to control MRSA infections. The present study revealed the non-antibacterial biofilm inhibitory potential of hesperidin against ATCC strain and clinical isolates of S. aureus. Hesperidin is a flavanone glycoside commonly found in citrus fruit. Hesperidin has been shown to exhibits numerous pharmacological activities. The present study aimed to evaluate the antibiofilm and antivirulence potential of hesperidin against MRSA. Results showed that hesperidin treatment significantly impedes lipase, hemolysin, autolysin, autoaggregation and staphyloxanthin production. Reductions of staphyloxanthin production possibly increase the MRSA susceptibility rate to H₂O₂ oxidative stress condition. In gene expression study revealed that hesperidin treatment downregulated the biofilm-associated gene (sarA), polysaccharide intracellular adhesion gene (icaA and icaD), autolysin (altA), fibronectin-binding protein (fnbA and fnbB) and staphyloxanthin production (crtM). Molecular docking analysis predicted the ability of hesperidin to interact with SarA and CrtM proteins involved in biofilm formation and staphyloxanthin production in MRSA.

3, 5-Di-tert-butylphenol combat against Streptococcus mutans by impeding acidogenicity, acidurance and biofilm formation

Streptococcus mutans is a common pathogen present in the oral cavity and it causes dental caries for all aged groups of people, in particular, children. S. mutans have several virulence factors such as acidogenecity, aciduricity, adhesion and biofilm formation. These virulence factors are working together and lead to the development of caries in the tooth surface. The present study aimed to investigate the anticariogenic potential of 3, 5-di-tert-butylphenol (3, 5-DTBP) against S. mutans. 3, 5-DTBP biofilm inhibitory concentration (BIC) was found at 100 µg/ml concentration without any lethal effect on the growth. Moreover, 3, 5-DTBP significantly reduced water soluble and water insoluble glucans production, in concurrence with downregulation of gtfBC genes. Moreover, acidogenicity associated virulence factors such as lactate dehydrogenase and enolase enzymatic production was arrested upon 3, 5-DTBP treatment. In addition, 3, 5-DTBP greatly reduced acidtolerance ability through impedes of F₁F₀-ATPase. Gene expression analysis unveiled the downregulation of gtfB, gtfC, gtfD, vicRK, comDE, gbpB, smu0630 and relA upon 3, 5-DTBP treatment. The present study paves the way for exhibiting 3, 5-DTBP as a promising therapeutic agent to control S. mutans infections.

Staphylococcus aureus: biofilm formation and strategies against it

The formation of Staphylococcus aureus biofilm causes significant infections in the human body. Biofilm forms through the aggregation of bacterial species and brings about many complications. It mediates drug resistance and persistence and facilitates the recurrence of infection at the end of antimicrobial therapy. Biofilm formation goes through a series of steps to complete, and any interference in these steps can disrupt its formation. Such interference may occur at any stage of biofilm production, including attachment, monolayer formation, and accumulation. Interfering agents can act as quorum sensing inhibitors and interfere in the functionality of quorum sensing receptors, attachment inhibitors and affect the cell hydrophobicity. Among these inhibiting strategies, attachment inhibitors could serve as the best agents against biofilm formation. If pathogens abort the attachment, the following stages of biofilm formation, e.g., accumulation and dispersion, will fail to materialize. Inhibition at this stage leads to suppression of virulence factors and invasion. One of the best-known inhibitors is a chelator that collects metal, Fe+, Zn+, and magnesium critical for biofilm formation. These influential factors in the binding and formation of biofilm are investigated, and the coping strategy is discussed. This review examines the stages of biofilm formation and determines what factors interfere in the continuity of these steps. Finally, the inhibition strategies are investigated, reviewed, and discussed. Keywords: Biofilm, Staphylococcus, Biofilm inhibitor, Dispersion, Antibiofilm agent, EPS, PIA.

Anti-quorum sensing and antibiofilm potential of 1,8-cineole derived from Musa paradisiaca against Pseudomonas aeruginosa strain PAO1

Pseudomonas aeruginosa is one of the vulnerable opportunistic pathogens associated with nosocomial infections, cystic fibrosis, burn wounds and surgical site infections. Several studies have reported that quorum sensing (QS) systems are controlled the P. aeruginosa pathogenicity. Hence, the targeting of QS considered as an alternative approach to control P. aeruginosa infections. This study aimed to evaluate the anti-quorum sensing and antibiofilm inhibitory potential of Musa paradisiaca against Chromobacterium violaceum (ATCC 12472) and Pseudomonas aeruginosa. The methanol extract of M. paradisiacsa exhibits that better antibiofilm potential against P. aeruginosa. Then, the crude methanol extract was subjected to purify by column chromatography and collected the fractions. The mass-spectrometric analysis of a methanol extract of M. paradisiaca revealed that 1,8-cineole is the major compounds. 1, 8-cineole significantly inhibited the QS regulated violacein production in C. violaceum. Moreover, 1,8-cineole significantly inhibited the QS mediated virulence production and biofilm formation of P. aeruginosa without affecting their growth. The real-time PCR analysis showed the downregulation of autoinducer synthase and transcriptional regulator genes upon 1,8-cineole treatment. The findings of the present study strongly suggested that metabolite of M. paradisiaca impedes P. aeruginosa QS system and associated virulence productions.

Anti-Biofilm Activity of Cell-Free Supernatant of Saccharomyces cerevisiae against Staphylococcus aureus

Staphylococcus aureus is one of the most common microorganisms and causes foodborne diseases. In particular, biofilm-forming S. aureus is more resistant to antimicrobial agents and sanitizing treatments than planktonic cells. Therefore, this study aimed to investigate the anti-biofilm effects of cell-free supernatant (CFS) of Saccharomyces cerevisiae isolated from cucumber jangajji compared to grapefruit seed extract (GSE). CFS and GSE inhibited and degraded S. aureus biofilms. The adhesion ability, auto-aggregation, and exopolysaccharide production of CFS-treated S. aureus, compared to those of the control, were significantly decreased. Moreover, biofilm-related gene expression was altered upon CFS treatment. Scanning electron microscopy images confirmed that CFS exerted anti-biofilm effects against S. aureus. Therefore, these results suggest that S. cerevisiae CFS has anti-biofilm potential against S. aureus strains.