Anti-methicillin-resistance Staphylococcus aureus (MRSA) compounds from Bauhinia kockiana Korth. And their mechanism of antibacterial activity

New bioactive secondary metabolites from the soil-derived Streptomyces sp. S045 and their anti-bacterial and anti-type III secretion system activities

A total of seven compounds were isolated from the ISP3 agar cultures of a soil-derived Streptomyces sp. S045 strain. Their structures were determined based on 1D, 2D NMR spectroscopic data, HR ESI mass spectroscopy, X-ray diffraction analysis and comparison with the reported data. The new compounds were identified to be (S)-4-(1-hydroxyethyl)quinoline-2-carboxamide (1) and methyl 4-(hydroxymethyl)-2-(4-methylpentyl)-4,5-dihydrofuran-3-carboxylate (3), respectively. Their anti-bacterial and anti-type III secretion system (T3SS) activities were evaluated.

Comparison of Antibacterial Activity of Phytochemicals against Common Foodborne Pathogens and Potential for Selection of Resistance

Antimicrobial resistance is now commonly observed in bacterial isolates from multiple settings, compromising the efficacy of current antimicrobial agents. Therefore, there is an urgent requirement for efficacious novel antimicrobials to be used as therapeutics, prophylactically or as preservatives. One promising source of novel antimicrobial chemicals is phytochemicals, which are secondary metabolites produced by plants for numerous purposes, including antimicrobial defence. In this report, we compare the bioactivity of a range of phytochemical compounds, testing their ability to directly inhibit growth or to potentiate other antimicrobials against Salmonella enterica Typhimurium, Pseudomonas aeruginosa, Listeria monocytogenes, and Staphylococcus aureus. We found that nine compounds displayed consistent bioactivity either as direct antimicrobials or as potentiators. Thymol at 0.5 mg/mL showed the greatest antimicrobial effect and significantly reduced the growth of all species, reducing viable cell populations by 66.8%, 43.2%, 29.5%, and 70.2% against S. enterica Typhimurium, S. aureus, P. aeruginosa, and L. monocytogenes, respectively. Selection of mutants with decreased susceptibility to thymol was possible for three of the pathogens, at a calculated rate of 3.77 × 10-8, and characterisation of S. enterica Typhimurium mutants showed a low-level MDR phenotype due to over-expression of the major efflux system AcrAB-TolC. These data show that phytochemicals can have strong antimicrobial activity, but emergence of resistance should be evaluated in any further development.

Antibacterial and Antimycotic Activity of Epilobium angustifolium L. Extracts: A Review

The aim of this work was to provide an overview of available information on the antibacterial and antifungal properties of Epilobium angustifolium extracts. A literature search of Scopus, PubMed/Medline, and Google Scholar for peer-reviewed articles published between January 2000 and June 2023 was undertaken. A total of 23 studies were eligible for inclusion in this review. Significant variation of antimicrobial activity depending on the tested species and strains, type of extract solvent, or plant organs utilized for the extract preparation was found. E. angustifolium extracts were active against both Gram-positive and Gram-negative bacteria and showed antimycotic effects against the fungi of Microsporum canis and Trichophyton tonsurans and the dermatophytes Arthroderma spp. Greater susceptibility of Gram-positive than Gram-negative bacteria to fireweed extracts was found. A strong antibacterial effect was recorded for Staphylococcus aureus, Bacillus cereus, Micrococcus luteus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii including multi-drug resistant strains. E. angustifolium extract might find practical application as an antimicrobial in wound healing, components of cosmetic products for human and animals, or as food preservatives.

Methicillin-Resistant Staphylococcus aurous: Epidemiology, Transmission and New Alternative Therapies: A Narrative Review

Over the last decade, we were facing medical struggle by the emergence of multi-resistant bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA). MRSA infections are still causing a growing global concern due to the rapid adaptive multidrug resistance to conventional antibiotics in human, community and veterinary medicine. Here we provide an overview about MRSA epidemiology, transmission and alternative potential treatments particularly new discovered phytochemicals with biological activity. In this narrative review, bibliographic data was collected from literature search databases: Google Scholar, web of science and PubMed/MEDLINE during recent years (2016 to 2021). MRSA is responsible of wide spectrum life threatening infections such us septicemia, endocarditis, and wound infections. It has epidemic potential in hospitals, that is responsible of most nosocomial infections leading to mortality and constitute a real burden for the healthcare systems. Effective preventive strategies for management of MRSA are highly required moreover, the identification and development of novel drugs or active biomolecules through phytochemicals are time challenging to face new resistant strains.

Antibacterial efficacy of Enterococcus microencapsulated bacteriocin on Listeria monocytogenes, Listeria innocua and Listeria ivanovi

This study focused on the microencapsulation of enterocin from Enterococcus durans (E. durans MF5) in whey powder (WP) using a spray-drying technique followed by the evaluation of how complexation can preserve the enterocin structure and antimicrobial activity against food-borne pathogens. Crude enterocin samples (1 and 5%) were microencapsulated in 10% WP. The antimicrobial activity of unencapsulated (crude) enterocin and microencapsulated enterocin was tested against the target bacteria Salmonella Typhimurium, Escherichia coli, Listeria monocytogenes, Listeria innocua, and Listeria ivanovi. The microencapsulation yields were 31.66% and 34.16% for concentrations of 1 and 5% enterocin, respectively. There was no significant difference between these concentrations. Microencapsulated enterocin was efficient for up to 12 h of cocultivation with Listeria sp., and the concentration required to inhibit the growth of target bacteria presented values of 6400 AU/mL (arbitrary unit). Microencapsulated enterocin demonstrated enhanced efficacy against Listeria species and E. coli when compared with crude enterocin (p < 0.05). Fourier transform-infrared spectroscopy and differential scanning calorimetry results confirmed the presence of enterocin in the microparticles. Scanning electron microscopy showed cell damage of the target bacteria. The results showed that complexation with WP preserved enterocin antimicrobial activity during spray-drying, indicating its potential use as a food preservative.

Multipronged Micelles-Hydrogel for Targeted and Prolonged Drug Delivery in Chronic Wound Infections

Chronic diabetic wounds are a growing threat globally. Many aspects contribute to its deterioration, including bacterial infection, unbalanced microenvironment, dysfunction of cell repair, etc. In this work, we designed a multipronged micelles-hydrogel platform loaded with curcumin and rifampicin (CRMs-hydrogel) for bacteria-infected chronic wound treatment. The curcumin- and rifampicin-loaded micelles (CRMs) exhibited both MMP9-responsive and epidermal growth factor receptor (EGFR)-targeting abilities. On the one hand, drugs could be released from micelles due to responsive disassembly by MMP9, a matrix metalloproteinase overexpressed in a chronic wound environment; on the other hand, CRMs showed specific targeting to EGFR on epithelial cells and fibroblasts and therefore increased intracellular drug delivery. The thermosensitive CRMs-hydrogel could form strong adhesion with the wound area and served as a suitable matrix for sustained release of CRMs directly at the wound bed, with excellent intracellular and extracellular bacterial elimination efficiency and wound healing promotion capability. We found that a single dose of CRMs-hydrogel achieved 99% antibacterial rate at the MRSA-infected diabetic wound, which effectively reduced inflammatory response and promoted the neovascularization and re-epithelialization process, with nearly half reduction of the skin barrier regeneration period. Collectively, our thermosensitive, MMP9-responsive, and targeted micelles-hydrogel nanoplatform is promising for chronic wound treatment.

Harnessing the Role of Bacterial Plasma Membrane Modifications for the Development of Sustainable Membranotropic Phytotherapeutics

Membrane-targeted molecules such as cationic antimicrobial peptides (CAMPs) are amongst the most advanced group of antibiotics used against drug-resistant bacteria due to their conserved and accessible targets. However, multi-drug-resistant bacteria alter their plasma membrane (PM) lipids, such as lipopolysaccharides (LPS) and phospholipids (PLs), to evade membrane-targeted antibiotics. Investigations reveal that in addition to LPS, the varying composition and spatiotemporal organization of PLs in the bacterial PM are currently being explored as novel drug targets. Additionally, PM proteins such as Mla complex, MPRF, Lpts, lipid II flippase, PL synthases, and PL flippases that maintain PM integrity are the most sought-after targets for development of new-generation drugs. However, most of their structural details and mechanism of action remains elusive. Exploration of the role of bacterial membrane lipidome and proteome in addition to their organization is the key to developing novel membrane-targeted antibiotics. In addition, membranotropic phytochemicals and their synthetic derivatives have gained attractiveness as popular herbal alternatives against bacterial multi-drug resistance. This review provides the current understanding on the role of bacterial PM components on multidrug resistance and their targeting with membranotropic phytochemicals.

Phytochemicals with activity against methicillin-resistant Staphylococcus aureus

BACKGROUND

The evolution of resistance to antimicrobials is a ubiquitous phenomenon. The evolution of antibiotic resistance in Staphylococcus aureus suggests that there is no remedy with sustaining effectiveness against this pathogen. The limited number of antibacterial drug classes and the common occurrence of cross-resistant bacteria reinforce the urgent need to discover new compounds targeting novel cellular functions. Natural products are a potential source of novel antibacterial agents. Anti-MRSA (methicillin-resistant S. aureus) bioactive compounds from Streptomyces and the anti-MRSA activity of a series of plant extracts have been reviewed respectively. However, there has been no detailed review of the precise bioactive components from plants.

PURPOSE

The present review aimed to summarize the phytochemicals that have been reported with anti-MRSA activities, analyze their structure-activity relationship and novel anti-MRSA mechanisms.

METHODS

Data contained in this review article are compiled from the authoritative databases PubMed, Web of Science, Google Scholar, and so on.

RESULTS

This review summarizes 100 phytochemicals (27 flavonoids, 23 alkaloids, 17 terpenes and 33 others) that have been tested for their anti-MRSA activity. Among these phytochemicals, 39 compounds showed remarkable anti-MRSA activity with MIC values less than 10 μg/ml, 14 compounds with MIC ranges including values < 10 μg/ml, 5 compounds with MIC values less than 5 μM; 11 phytochemicals show synergism anti-MRSA effects in combination with antibiotics. Phytochemicals exerted anti-MRSA activities mainly by destroying the membrane structure and inhibiting the efflux pump.

CONCLUSIONS

The 58 compounds with excellent anti-MRSA activity the 11 compounds with synergistic anti-MRSA effect, especially cannabinoids, xanthones and fatty acids should be further studied in vitro. Novel targets, such as cell membrane and efflux pump could be promising alternatives to develop antibacterial drugs in the future in order to prevent drug resistance.

Antibacterial plant compounds, extracts and essential oils: An updated review on their effects and putative mechanisms of action

BACKGROUND

Antibiotic-resistant bacteria pose a global health threat. Traditional antibiotics can lose their effectiveness, and the development of novel effective antimicrobials has become a priority in recent years. In this area, plants represent an invaluable source of antimicrobial compounds with vast therapeutic potential.

PURPOSE

To review the full possible spectrum of plant antimicrobial agents (plant compounds, extracts and essential oils) discovered from 2016 to 2021 and their potential to decrease bacterial resistance. Their activities against bacteria, with special emphasis on multidrug resistant bacteria, mechanisms of action, possible combinations with traditional antibiotics, roles in current medicine and future perspectives are discussed.

METHODS

Studies focusing on the antimicrobial activity of compounds of plant origin and their mechanism of action against bacteria were identified and summarized, including contributions from January 2016 until January 2021. Articles were extracted from the Medline database using PubMed search engine with relevant keywords and operators.

RESULTS

The search yielded 11,689 articles from 149 countries, of which 101 articles were included in this review. Reports from 41 phytochemicals belonging to 20 families were included. Reports from plant extracts and essential oils from 39 plant species belonging to 17 families were also included. Polyphenols and terpenes were the most active phytochemicals studied, either alone or as a part of plant extracts or essential oils. Plasma membrane disruption was the most common mechanism of antimicrobial action. Number and position of phenolic hydroxyl groups, double bonds, delocalized electrons and conjugation with sugars in the case of flavonoids seemed to be crucial for antimicrobial capacity. Combinations of phytochemicals with beta-lactam antibiotics were the most studied, and the inhibition of efflux pumps was the most common synergistic mechanism.

CONCLUSION

In recent years, terpenes, flavones, flavonols and some alkaloids and phenylpropanoids, either isolated or as a part of extracts, have shown promising antimicrobial activity, being membrane disruption their most common mechanism. However, their utilization as appropriate antimicrobials need to be boosted by means of new omics technologies and network pharmacology to find the most effective combinations among them or in combination with antibiotics.

Loranthus acaciae: Alternative medicine for β-lactamase producer and methicillin-resistant Staphylococcus aureus

Recently, we reported high antibacterial efficiency of Loranthus acaciae (LA) against different standard strains of bacteria including Methicillin-Resistant Staphylococcus aureus (MRSA). Therefore, this study aimed to confirm the effectiveness of LA against clinically isolated Staphylococcus aureus (SA) including β-lactamase producer (Blac) and MRSA. Forty-eight SA isolates collected from various clinical samples were used in this study. Antibiotics susceptibility profile was determined for twenty different antibiotics using automated Microscan Walkaway 96 Plus system as recommended by Clinical and Laboratory Standards Institute (CLSI) guidelines. This system also identified β-lactamase producers and MRSA. In the meantime, LA ethanolic extract was fractionated using liquid-liquid fraction method to hexane, dichloromethane DCM and methanol 80% fractions. Antimicrobial activities of LA extract and fraction were performed with agar well diffusion method for all SA isolates, MIC and MBC were also recorded. Phytochemical screening for various phyto-constituent classes of LA ethanolic extract was determined. Out of 48 SA isolates, Cefoxitin-positive MRSA represent 31 (64.6%), Blac 17 (35.4%), and 41 (85.4%) were multidrug-resistant SA, which was resistant at least to one antibiotic from three different categories. All isolates were resistant to ampicillin and penicillin. Antimicrobial activities of LA extract and fractions revealed that ethanol extract was active against all isolated SA with inhibition zone ranged from 33 ± 2.00 to 25 ± 3.05 mm. While DCM exhibited the largest inhibition zone range from 37 ± 3.00 to 33 ± 2.00 mm. This study is first of its kind conforming the high antibacterial activity of LA against SA isolated from a different source of infection. The study concluded that LA extract and fractions are active and give positive result for all isolated SA. Therefore, suitable pharmacological formulation of LA extract as a promising antibacterial agent for the treatment of SA infection should be given extreme priority.

Antibacterial Activity of Bandotan (Ageratum conyzoides L) Leaves Extracts Against Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of nosocomial infections throughout the world and can be life-threatening as well. This study aimed to determine the antibacterial activity of Bandotan (Ageratum conyzoides L) leaves ethanolic extract against MRSA's growth. Ageratum conyzoides leaves were extracted by ethanol and screened for their phytochemical constituent. Ethanolic extracts of A. conyzoides leaves were evaluated for their potential antibacterial activity using disc diffusion assay. The minimum inhibitory concentration (MIC) value was determined using the agar dilution method. Phytochemical screening shows that the extracts contain alkaloids, flavonoids, saponins, tannins, and steroids or triterpenoids. Ageratum conyzoides leaves extract shows a 25.1 mm inhibitory zone at 12.5% extract concentration with MIC value equivalents to 4.46 x 10-6 g of gentamicin. This study concludes that A. conyzoides leaves ethanolic extracts have potential antibacterial activity against MRSA.

Graphene Oxide affects Staphylococcus aureus and Pseudomonas aeruginosa dual species biofilm in Lubbock Chronic Wound Biofilm model

Chronic wound management becomes a complex procedure because of the persistence of forming biofilm pathogens that do not respond to antimicrobial treatment. The aim of this paper is to detect the Graphene Oxide-GO effect on Staphylococcus aureus and Pseudomonas aeruginosa dual species wound biofilm in Lubbock Chronic Wound Biofilm-LCWB model. LCWB is a recognized model that mimics the spatial microbial colonization into chronic wounds and reproduces the wound and its clot. Staphylococcus aureus PECHA 10 and P. aeruginosa PECHA 4, are the pathogens used in the study. The GO effect on both in forming and mature biofilms, is detected by the evaluation of the CFU/mg reduction, the cell viability and ultrastructural analysis of the treated LCWBs. Graphene Oxide, at 50 mg/l, shows a significant antibiofilm effect in forming and mature LCWBs. In particular, during the biofilm formation, GO reduces the S. aureus and P. aeruginosa growth of 55.05% ± 4.73 and 44.18% ± 3.91 compared to the control. In mature biofilm, GO affects S. aureus and P. aeruginosa by reducing their growth of 70.24% ± 4.47 and 63.68% ± 17.56, respectively. Images taken by SEM show that GO display a disaggregated microbial effect also disrupting the fibrin network of the wound-like biofilm framework. In conclusion, GO used against microorganisms grown in LCWB, displays a significant inhibitory action resulting in a promising tool for potential application in wound management.

Catechin isolated from cashew nut shell exhibits antibacterial activity against clinical isolates of MRSA through ROS-mediated oxidative stress

Staphylococcus aureus causes severe infections and among all methicillin-resistant S. aureus (MRSA) remains a great challenge in spite of decade research of antibacterial compounds. Even though some synthetic antibiotics have been developed, they are not effective against MRSA, and hence, there is a search for natural, alternative and plant-based antibacterial compound. In this connection, catechin isolated from cashew nut shell was investigated for its antibacterial potential against MRSA. Catechin exhibited zone of inhibition (ZOI) and minimum inhibitory concentration (MIC) in a range of 15.1-19.5 mm and 78.1-156.2 μg/ml, respectively, against ATCC and clinical isolates of MRSA. Among all clinical isolates, clinical isolate-3 exhibited highest sensitivity to catechin. Catechin has arrested the growth of MRSA strains and also caused toxicity by membrane disruption which was illustrated by AO/EB fluorescence staining. Increased nucleic acid leakage (1.58-28.6-fold) and protein leakage (1.40-23.50-fold) was noticed in MRSA due to catechin treatment when compared to methicillin. Bacteria treated with catechin at its MIC showed 1.52-, 1.87- and 1.74-fold increase of ROS production in methicillin susceptible S. aureus (MSSA), MRSA and clinical isolate-3 strains, respectively, as compared to control. Superoxide dismutase (5.31-9.63 U/mg protein) and catalase (1573-3930 U/mg protein) were significantly decreased as compared to control in catechin-treated S. aureus. Thus, catechin exhibited antibacterial activity through oxidative stress by increased production of ROS and decreased antioxidant enzymes. Altogether results suggest that catechin is a promising lead compound with antibacterial potential against MRSA. KEY POINTS: • Catechin was isolated and identified as active compound in cashew nut shell. • Catechin exhibited antimicrobial activity against clinical isolates of MRSA. • Bacterial cell wall damage was caused by catechin in MRSA strains. • Catechin increased the oxidative stress in MRSA by intracellular ROS production.

Hexyl gallate for the control of citrus canker caused by Xanthomonas citri subsp citri

Brazil is the biggest producer of sweet oranges and the main exporter of concentrated orange juice in the world. Among the diseases that affect citriculture, Asiatic citrus canker, caused by the bacterial pathogen Xanthomonas citri, represents one of the most significant threats. The current Brazilian legislation regulating the control of citrus canker no longer requires the eradication of affected trees in states where the incidence of the disease is high. Instead, control involves disease control measures, including periodic preventative spraying of copper compounds. The long-term use of copper for plant disease control has raised concerns about environmental accumulation and toxicity, as well as the selective pressure it exerts leading to the emergence of copper-resistant X. citri strains. Here, we evaluated hexyl gallate (G6) as an alternative to copper compounds for citrus plant protection. G6 was able to protect citrus nursery trees against X. citri infection. Thirty days after inoculation, the trees treated with G6 developed 0.5 lesions/cm² leaf area compared with the 2.84 lesions/cm² observed in the untreated control trees. Also, G6 did not interfere with germination and root development of tomato, lettuce, and arugula, which is consistent with our previous data showing that G6 is safe for tissue culture cell lines. Membrane permeability tests showed that the primary target of G6 is the bacterial outer membrane. Finally, we could not isolate spontaneous X. citri mutants resistant to G6 nor induce resistance to G6 after long-term exposures to increasing concentrations of the compound, which suggests that G6 may have multiple cellular targets. This study demonstrated that G6 is a promising candidate for the development and use in citrus canker management.

Progress and prospects in the management of bacterial infections and developments in Phytotherapeutic modalities

The advent of antibiotics revolutionized medical care resulting in significantly reduced mortality and morbidity caused by infectious diseases. However, excessive use of antibiotics has led to the development of antibiotic resistance and indeed, the incidence of multidrug-resistant pathogens is considered as a major disadvantage in medication strategy, which has led the scholar's attention towards innovative antibiotic sources in recent years. Medicinal plants contain a variety of secondary metabolites with a wide range of therapeutic potential against the resistant microbes. Therefore, the aim of this review is to explore the antibacterial potential of traditional herbal medicine against bacterial infections. More than 200 published research articles reporting the therapeutic potential of medicinal plants against drug-resistant microbial infections were searched using different databases such as Google Scholar, Science Direct, PubMed and the Directory of Open Access Journals (DOAJ), etc., with various keywords like medicinal plants having antibacterial activities, antimicrobial potentials, phytotherapy of bacterial infection, etc. Articles were selected related to the efficacious herbs easily available to local populations addressing common pathogens. Various plants such as Artocarpus communis, Rheum emodi, Gentiana lutea L., Cassia fistula L., Rosemarinus officinalis, Argemone maxicana L, Hydrastis canadensis, Citrus aurantifolia, Cymbopogon citrates, Carica papaya, Euphorbia hirta, etc, were found to have significant antibacterial activities. Although herbal preparations have promising potential in the treatment of multidrug-resistant bacterial infection, still more research is required to isolate phytoconstituents, their mechanism of action as well as to find their impacts on the human body.

Tellimagrandin II, A Type of Plant Polyphenol Extracted from Trapa bispinosa Inhibits Antibiotic Resistance of Drug-Resistant Staphylococcus aureus

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) has become a critical global concern. Identifying new candidates of anti-S. aureus agents is urgently required because the therapeutic strategies for infected patients are limited currently. Therefore, the present study investigated whether Tellimagrandin II (TGII), a pure compound extracted from the shells of Trapa bispinosa, exhibits antibacterial effects against MRSA. We first showed that TGII exerted potent inhibitory activity against MRSA with a minimum inhibitory concentration of 128 μg/mL. The obtained fractional inhibitory concentration suggested that TGII could alone exert antistaphylococcal activity, and TGII combined with low doses of antibiotics displayed synergistic effects against MRSA. Moreover, we found that TGII exerted bactericidal activity by reducing the expression of mecA followed by the negative regulation of the penicillin-binding protein 2a (PBP2a) of MRSA. Transmission electron microscopy (TEM) images further confirmed that TGII destroyed the integrity of the cell wall of MRSA and caused the loss of cytoplasm content. In conclusion, we evidenced the antibacterial effects of TGII against MRSA, which enables the effective dose of current antibiotics to be reduced and the predicament of drug-resistant S. aureus isolates to be overcome.

Antimicrobial activity and active compounds of a Rhus verniciflua Stokes extract

The Rhus verniciflua Stokes (RVS) extract is used as a traditional herbal medicine in Southeast Asian countries such as Korea and China. In the present study, one phenolic acid and six flavonoids were isolated from an 80% ethanol RVS extract to examine their antimicrobial activities. These compounds were identified as 3',4',7-trihydroxyflavone (1), methyl gallate (2), gallic acid (3), fusti (4), fisetin (5), butin (6), and sulfuretin (7) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nuclear magnetic resonance spectroscopy. The antimicrobial activities of compounds 5 and 6 (at a dose of 16 μg/mL each) were superior to that of the control, cycloheximide (at a dose of 25 μg/mL), against Hypocrea nigricans; additionally, the activities of compounds 1 and 2 (at a dose of 8 μg/mL each) were superior to the control against Penicillium oxalicum. Also, chemical compounds 1 and 5 (at a dose of 16 μg/mL each) had higher activities than the control (25 μg/mL) against Trichoderma virens. Chemical compound 1 (at a dose of 8 μg/mL) had a similar activity to that of the control against Bacillus subtilis. The obtained results suggest that the RVS extract could be a promising food and nutraceutical source because of the antimicrobial properties of its phenolic compounds.

Discovery of Potential Plant-Derived Peptide Deformylase (PDF) Inhibitors for Multidrug-Resistant Bacteria Using Computational Studies

Bacterial peptide deformylase (PDF) is an attractive target for developing novel inhibitors against several types of multidrug-resistant bacteria. The objective of the current study is to retrieve potential phytochemicals as prospective drugs against Staphylococcus aureus peptide deformylase (SaPDF). The current study focuses on applying ligand-based pharmacophore model (PharmL) and receptor-based pharmacophore (PharmR) approaches. Utilizing 20 known active compounds, pharmL was built and validated using Fischer's randomization, test set method and the decoy set method. PharmR was generated from the knowledge imparted by the Interaction Generation protocol implemented on the Discovery Studio (DS) v4.5 and was validated using the decoy set that was employed for pharmL. The selection of pharmR was performed based upon the selectivity score and further utilizing the Pharmacophore Comparison module available on the DS. Subsequently, the validated pharmacophore models were escalated for Taiwan Indigenous Plants (TIP) database screening and furthermore, a drug-like evaluation was performed. Molecular docking was initiated for the resultant compounds, employing CDOCKER (available on the DS) and GOLD. Eventually, the stability of the final PDF⁻hit complexes was affirmed using molecular dynamics (MD) simulation conducted by GROMACS v5.0.6. The redeemed hits demonstrated a similar binding mode and stable intermolecular interactions with the key residues, as determined by no aberrant behaviour for 50 ns. Taken together, it can be stated that the hits can act as putative scaffolds against SaPDF, with a higher therapeutic value. Furthermore, they can act as fundamental structures for designing new drug candidates.

Novel antibacterial modalities against methicillin resistant Staphylococcus aureus derived from plants

Methicillin-resistant Staphylococcus aureus (MRSA) is a notorious bacterial pathogen that induces high mortality and morbidity. Due to the emergence of multiple resistance, antibiotic treatments are rapidly becoming ineffective for the related infections. Natural products, especially those derived from plants, have been proven to be effective agents with unique antibacterial properties through different mechanisms. This review interprets the resistance mechanisms of MRSA with the aim to conquer public health threat. Further, recent researches about plant antimicrobials that showed remarkable antibacterial activity against MRSA are recorded, including the crude plant extracts and purified plant-derived bioactive compounds. Novel anti-MRSA modalities of plant antimicrobials such as alteration in efflux pump, inhibition of pyruvate kinase, and disturbance of quorum sensing in MRSA are also summarized which may be promising alternatives to antibacterial drug development in future.