Ellagic acid derivatives from Rubus ulmifolius inhibit Staphylococcus aureus biofilm formation and improve response to antibiotics

Synthetic Ellagic Acid Glycosides Inhibit Early Stage Adhesion of Streptococcus agalactiae Biofilms as Observed by Scanning Electron Microscopy

Ellagic acid derivatives possess antimicrobial and antibiofilm properties across a wide-range of microbial pathogens. Due to their poor solubility and ambident reactivity it is challenging to synthesize, purify, and characterize the activity of ellagic acid glycosides. In this study, we have synthesized three ellagic acid glycoconjugates and evaluated their antimicrobial and antibiofilm activity in Streptococcus agalactiae (Group B Streptococcus, GBS). Their significant impacts on biofilm formation were examined via SEM to reveal early-stage inhibition of cellular adhesion. Additionally, the synthetic glycosides were evaluated against five of the six ESKAPE pathogens and two fungal pathogens. These studies reveal that the ellagic acid glycosides possess inhibitory effects on the growth of gram-negative pathogens.

Triterpenoid acids isolated from Schinus terebinthifolia fruits reduce Staphylococcus aureus virulence and abate dermonecrosis

Staphylococcus aureus relies on quorum sensing to exert virulence to establish and maintain infection. Prior research demonstrated the potent quorum sensing inhibition effects of "430D-F5", a refined extract derived from the fruits of Schinus terebinthifolia, a medicinal plant used for the traditional treatment of skin and soft tissue infections. We report the isolation and identification of three compounds from 430D-F5 that reduce virulence and abate dermonecrosis: 3-oxo-olean-12-en-28-oic acid (1), 3-oxotirucalla-7,24Z-dien-26-oic acid (2) and 3α-hydroxytirucalla-7,24 Z-dien-27-oic acid (3). Each compound inhibits all S. aureus accessory gene regulator (agr) alleles (IC50 2-70 μM). Dose-dependent responses were also observed in agr-regulated reporters for leucocidin A (lukA, IC50 0.4-25 μM) and glycerol ester hydrolase or lipase (gehB, IC50 1.5-25 μM). Surprisingly, dose-dependent activity against the nuclease reporter (nuc), which is under the control of the sae two-component system, was also observed (IC50 0.4-12.5 μM). Compounds 1-3 exhibited little to no effect on the agr-independent mgrA P2 reporter (a constitutive promoter from the mgrA two-component system) and the esxA reporter (under control of mgrA). Compounds 1-3 inhibited δ-toxin production in vitro and reduced dermonecrosis in a murine in vivo model. This is the first report of triterpenoid acids with potent anti-virulence effects against S. aureus.

Calpurnia aurea (Aiton) Benth Extracts Reduce Quorum Sensing Controlled Virulence Factors in Pseudomonas aeruginosa

Pseudomonas aeruginosa is the causative agent of several life-threatening human infections. Like many other pathogens, P. aeruginosa exhibits quorum sensing (QS) controlled virulence factors such as biofilm during disease progression, complicating treatment with conventional antibiotics. Thus, impeding the pathogen's QS circuit appears as a promising alternative strategy to overcome pseudomonas infections. In the present study, Calpurnia aurea were evaluated for their antibacterial (minimum inhibitory concentrations (MIC)), anti-quorum sensing/antivirulence (AQS), and antibiofilm potential against P. aeruginosa. AQS and antivirulence (biofilm formation, swimming, and swarming motility) activities of plant extracts were evaluated against Chromobacterium violaceum and P. aeruginosa, respectively. The in vitro AQS potential of the individual compounds were validated using in silico molecular docking. Acetone and ethanolic extracts of C. aurea showed MIC at 1.56 mg/mL. The quantitative violacein inhibition (AQS) assay showed ethyl acetate extracts as the most potent at a concentration of 1 mg/mL. GCMS analysis of C. aurea revealed 17 compounds; four (pentadecanol, dimethyl terephthalate, terephthalic acid, and methyl mannose) showed potential AQS through molecular docking against the CviR protein of C. violaceum. Biofilm of P. aeruginosa was significantly inhibited by ≥60% using 1-mg/mL extract of C. aurea. Confocal laser scanning microscopy correlated the findings of crystal violet assay with the extracts significantly altering the swimming motility. C. aurea extracts reduced the virulence of pseudomonas, albeit in a strain- and extract-specific manner, showing their suitability for the identification of lead compounds with QS inhibitory potential for the control of P. aeruginosa infections.

Chronic wound biofilms: diagnosis and therapeutic strategies

OBJECTIVE

To review the diagnosis of chronic wound biofilms and discuss current treatment approaches.

DATA SOURCES

Articles included in this review were obtained from the following databases: Wanfang, China National Knowledge Infrastructure, PubMed, and the Web of Science. We focused on research published before August 2019 with keywords including chronic wound, biofilm, bacterial biofilms, and chronic wound infection.

STUDY SELECTION

Relevant articles were selected by carefully reading the titles and abstracts. Further, different diagnosis and clinical treatment methods for chronic wound biofilm were compared and summarized from the selected published articles.

RESULTS

Recent guidelines on medical biofilms stated that approaches such as the use of scanning electron microscopy and confocal laser scanning microscopy are the most reliable types of diagnostic techniques. Further, therapeutic strategies include debridement, negative pressure wound therapy, ultrasound, antibiotic, silver-containing dressing, hyperbaric oxygen therapy, and others.

CONCLUSION

This review provides the identification and management of biofilms, and it can be used as a tool by clinicians for a better understanding of biofilms and translating research to develop best clinical practices.

Synergistic combinations of azoles and antihistamines against Candida species in vitro

Fungal infections are a major cause of skin and mucosal membrane disease. Immunocompromised individuals, such as those undergoing chemotherapy, are most susceptible to fungal infections. With a growing population of immunocompromised patients, there are many reports of increasing numbers of infections and of fungal strains resistant to current antifungals. One way to treat drug-resistant infections is to administer combinations of drugs to patients. Azoles are the most prescribed antifungals, as they are broad-spectrum and orally bioavailable. Terfenadine (TERF) and ebastine (EBA) are second-generation antihistamines, with EBA being used in many countries. In this study, we explored combinations of seven azole antifungals and two antihistamines (TERF and EBA) against a panel of 13 Candida fungal strains. We found 55 out of 91 combinations tested of TERF and EBA against the various fungal strains to be synergistic with the azoles. To evaluate the efficiency of these combinations to inhibit fungal growth, we performed time-kill assays. We also investigated the ability of these combinations to disrupt biofilm formation. Finally, we tested the specificity of the combinations towards fungal cells by mammalian cytotoxicity assays. These findings suggest a potential new strategy for targeting drug-resistant Candida infections.

Anti quorum sensing and anti virulence activity of tannic acid and it's potential to breach resistance in Salmonella enterica Typhi / Paratyphi A clinical isolates

Salmonella enterica Typhi and Paratyphi A are food borne pathogens causing typhoid, which is one of the most important food borne disease in the developing world. S. Typhi and S. Paratyphi A are of much concern as multi drug resistance has been on the rise. The current study is aimed to screen phytochemicals for anti quorum sensing (QS) activity against S. Typhi and S. Paratyphi A. Upon screening with swarming assay, tannic acid (TA) showed highest anti-QS activity with minimal concentration of 400μg/ml. The anti-QS activity of TA was confirmed with C. violaceum ATCC 12,472. TA showed 38-43% and 35-50% of inhibition in cell surface hydrophobicity and EPS production respectively. Through FTIR analysis, it has been observed that EPS of treated cells has a considerable change in protein and peptide. TA has also exhibited drastic reduction in the surfactant production as high as 85-90%. Blood sensitivity and antibiotic sensitivity assay revealed that TA significantly sensitizes the S. Typhi and S. Paratyphi A cells to immune components in human blood and antibiotics. It has reduced the resistance of S. Typhi and S. Paratyphi A cells against amikacin, ampicillin, ciprofloxacin, azithromycin, chloramphenicol and gentamycin, thus revitalized the usage of these antibiotics against drug resistant S. Typhi and S. Paratyphi A infections. The consistency of anti-QS potential of TA was further evaluated and established with another eight clinical isolates of S. Typhi and S. Paratyphi A. Thus TA has been proved as a promising anti QS agent that can be developed as a therapeutic combination against S. Typhi and S. Paratyphi A.

Rhamnus prinoides (gesho): A source of diverse anti-biofilm activity

ETHNOPHARMACOLOGICAL RELEVANCE

Rhamnus prinoides (gesho) is an evergreen shrub from East Africa traditionally used for the treatment of illnesses including atopic dermatitis, ear, nose and throat infections, pneumonia, arthritis, brucellosis, flu, indigestion and fatigue.

AIM OF THE STUDY

Several of the conditions for which gesho is traditionally used are associated with communities of surface-attached microorganisms, or biofilms. We hypothesized that gesho has anti-biofilm activity. The principal aim of this study was to evaluate gesho-associated anti-biofilm activity and identify active compounds.

MATERIALS AND METHODS

Lyophilized ethanol and aqueous extracts were prepared from dried Rhamnus prinoides stems and leaves. Biofilm inhibition was measured by crystal violet staining and subsequent viability assays were conducted on growth agar. Chemical fractionation, chemical testing, Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) were used to isolate and identify active compounds.

RESULTS

Leaf and stem ethanol extracts significantly inhibited Staphylococcus aureus, Bacillus subtilis and Streptococcus mutans biofilm formation up to 99.9% and reduced planktonic cell growth up to 10 log units relative to untreated controls. The anti-biofilm activity of the ethanol stem extracts was due to a biocidal or bacteriostatic mechanism while bacteriostatic or anti-pathogenic mechanisms were attributed to the leaf ethanol extract. Gesho extracts showed activity against all three species tested but the treatment efficacy and mechanism were species dependent. Chemical fractionation and activity screens of the leaf ethanol extract identified ethyl 4-ethoxybenzoate and 4-hydroxy 4-methyl pentanone to be compounds with anti-biofilm activity. Ethyl 4-ethoxybenzoate activity was potentiated by DMSO. Notably, concentrations of both compounds were identified where biofilm formation was prevented without inhibition of cell growth; i.e. anti-pathogenic characteristics were evident.

CONCLUSION

Gesho leaf ethanol extract contains chemicals with anti-biofilm and bactericidal activities. This work lends support to the traditional use of gesho for treating topical infections and warrants further investigation into Rhamnus prinoides as a source of antibacterial and anti-biofilm agents.

Molecular Mechanisms of Leonurus Cardiaca L. Extract Activity in Prevention of Staphylococcal Endocarditis-Study on in Vitro and ex Vivo Models

Better understanding the mechanisms of Leonurus cardiaca L. extract (LCE) activity is necessary to prepare recommendations for the use of LCE-based herbal products for preventive/supportive purposes in case of infective endocarditis (IE) and other staphylococcal invasive infections. The aim of the study was to analyze molecular mechanisms of LCE effect on Staphylococcus aureus and blood platelets in the context of their interactions playing a pivotal role in such disorders. Using atomic force microscopy, we demonstrated that adhesion forces of S. aureus were markedly reduced after exposure to LCE at subinhibitory concentrations. The effect resulted from the impact of LCE on S. aureus cell morphology and the composition of phospholipids and fatty acids in bacterial membranes (assessed by HPLC), which modulated their stabilization, hydrophobicity, and charge. Moreover, using FACS we showed also that LCE significantly reduced GP IIb/IIIa expression on blood platelets, thus the disruption of platelet-fibrinogen interactions seems to explain antiplatelet effect of LCE. The obtained results prove the usefulness of LCE in the prevention of S. aureus adhesion, platelet activation, and vegetations development, however, also pointed out the necessity of excluding the cationic antibiotics from the treatment of S. aureus-associated IE and other invasive diseases, when motherwort herb is used simultaneously as an addition to the daily diet.

Ruthenium Chloride-Induced Oxidative Cyclization of Trans-Resveratrol to (±)-ε-Viniferin and Antimicrobial and Antibiofilm Activity Against Streptococcus pneumoniae

Polyphenol ε-viniferin (2) is a protective phytochemical found in several plant families. Here, we report a simple and effective method for the synthesis of (±)-ε-viniferin (2) as major product and (±)-(E)-ω-viniferin (3) as a minor product. Synthesized viniferin compounds and standard viniferin were analyzed for antibacterial and antibiofilm activity against Gram-positive bacteria Streptococcus pneumoniae. The minimum inhibitory concentrations (MICs) of (±)-ε-viniferin (2) and standard viniferin were 20 µm. However, the MICs of (±)-(E)-ω-viniferin (3) and compound 8 were 40 µm. Although viniferin significantly (p < 0.05) reduced pre-established in vitro biofilms and killed bacteria within the biofilm, it was unable to prevent biofilm formation at sub-MIC concentrations. The time kill experiment revealed that viniferin killed bacteria and reduced 2.8 log10 bacteria at 2 × MIC concentration after 24 h. Scanning electron microscope (SEM) analysis and live/dead biofilm staining of pre-established biofilms revealed that viniferin treatment disrupts membrane integrity of biofilm bacteria. Crystal violet absorption, total protein, and DNA and RNA release revealed that viniferin alters bacterial cell permeability, eventually killing bacteria.

Methicillin-resistant Staphylococcus aureus (MRSA): antibiotic-resistance and the biofilm phenotype

Staphylococcus aureus (S. aureus) is an asymptomatic colonizer of 30% of all human beings. While generally benign, antibiotic resistance contributes to the success of S. aureus as a human pathogen. Resistance is rapidly evolved through a wide portfolio of mechanisms including horizontal gene transfer and chromosomal mutation. In addition to traditional resistance mechanisms, a special feature of S. aureus pathogenesis is its ability to survive on both biotic and abiotic surfaces in the biofilm state. Due to this characteristic, S. aureus is a leading cause of human infection. Methicillin-resistant S. aureus (MRSA) in particular has emerged as a widespread cause of both community- and hospital-acquired infections. Currently, MRSA is responsible for 10-fold more infections than all multi-drug resistant (MDR) Gram-negative pathogens combined. Recently, MRSA was classified by the World Health Organization (WHO) as one of twelve priority pathogens that threaten human health. In this targeted mini-review, we discuss MRSA biofilm production, the relationship of biofilm production to antibiotic resistance, and front-line techniques to defeat the biofilm-resistance system.

American Civil War plant medicines inhibit growth, biofilm formation, and quorum sensing by multidrug-resistant bacteria

A shortage of conventional medicine during the American Civil War (1861–1865) spurred Confederate physicians to use preparations of native plants as medicines. In 1863, botanist Francis Porcher compiled a book of medicinal plants native to the southern United States, including plants used in Native American traditional medicine. In this study, we consulted Porcher’s book and collected samples from three species that were indicated for the formulation of antiseptics: Liriodendron tulipifera, Aralia spinosa, and Quercus alba. Extracts of these species were tested for the ability to inhibit growth in three species of multidrug-resistant pathogenic bacteria associated with wound infections: Staphylococcus aureus, Klebsiella pneumoniae, and Acinetobacter baumannii. Extracts were also tested for biofilm and quorum sensing inhibition against S. aureus. Q. alba extracts inhibited growth in all three species of bacteria (IC₅₀ 64, 32, and 32 µg/mL, respectively), and inhibited biofilm formation (IC₅₀ 1 µg/mL) in S. aureus. L. tulipifera extracts inhibited biofilm formation (IC₅₀ 32 µg/mL) in S. aureus. A. spinosa extracts inhibited biofilm formation (IC₅₀ 2 µg/mL) and quorum sensing (IC₅₀ 8 µg/mL) in S. aureus. These results support that this selection of plants exhibited some antiseptic properties in the prevention and management of wound infections during the conflict.

Validation of a 16th Century Traditional Chinese Medicine Use of Ginkgo biloba as a Topical Antimicrobial

In the search for new therapeutic solutions to address an increasing number of multidrug-resistant bacterial pathogens, secondary metabolites from plants have proven to be a rich source of antimicrobial compounds. Ginkgo biloba, a tree native to China, has been spread around the world as an ornamental tree. Its seeds have been used as snacks and medical materials in Traditional Chinese Medicine (TCM), while over the last century its leaf extracts emerged as a source of rising pharmaceutical commerce related to brain health in Western medicine. Besides studies on the neuro-protective effects of Ginkgo, its antibacterial activities have gained more attention from researchers in the past decades, though its leaves were the main focus. We reviewed a 16th-century Chinese text, the Ben Cao Gang Mu by Li Shi-Zhen, to investigate the ancient prescription of Ginkgo seeds for skin infections. We performed antibacterial assays on various Ginkgo seed extracts against pathogens (Staphylococcus aureus, Cutibacterium acnes, Klebsiella pneumoniae, Acinetobacter baumannii, Streptococcus pyogenes) relevant to skin and soft tissue infections (SSTIs). We demonstrate here that Ginkgo seed coats and immature seeds exhibit antibacterial activity against Gram-positive skin pathogens (C. acnes, S. aureus, and S. pyogenes), and thus validated its use in TCM. We also identified one compound tied to the antibacterial activity observed, ginkgolic acid C15:1, and examine its toxicity to human keratinocytes. These results highlight the relevance of ancient medical texts as leads for the discovery of natural products with antimicrobial activities.

The Contribution of Complementary and Alternative Medicine to Reduce Antibiotic Use: A Narrative Review of Health Concepts, Prevention, and Treatment Strategies

AIM

The aim of this narrative review was to explore the potential contributions of CAM to reduce antibiotic use.

METHODS

We searched PubMed, Embase, and Cochrane Database of Systematic Reviews with a specific, limited set of search terms and collected input from a group of expert CAM researchers to answer the question: What is known about the contribution of CAM health and health promotion concepts, infection prevention, and infection treatment strategies to reduce antibiotic use? Results. The worldview-related CAM health concepts enable health promotion oriented infection prevention and treatment aimed at strengthening or supporting the self-regulating ability of the human organism to cope with diseases. There is some evidence that the CAM concepts of health (promotion) are in agreement with current conceptualization of health and that doctors who practice both CAM and conventional medicine prescribe less antibiotics, although selection bias of the presented studies cannot be ruled out. There is some evidence that prevention and some treatment strategies are effective and safe. Many CAM treatment strategies are promising but overall lack high quality evidence.

CONCLUSIONS

CAM prevention and treatment strategies may contribute to reducing antibiotic use, but more rigorous research is necessary to provide high quality evidence of (cost-)effectiveness.

Insight into the effect of quinic acid on biofilm formed byStaphylococcus aureus

The biofilm formation of Staphylococcus aureus on food contact surfaces is the main risk of food contamination. In the present study, we firstly investigated the inhibitory effect of quinic acid (QA) on biofilm formed by S. aureus. Crystal violet staining assay and microscopy analysis clearly showed that QA at sub-MIC concentrations was able to significantly reduce the biofilm biomass and cause a collapse on biofilm architecture. Meanwhile, fibrinogen binding assay showed that QA had obviously effect on the S. aureus bacteria adhesion. XTT reduction assay and confocal laser scanning microscopic images revealed that QA significantly decreased metabolic activity and viability of biofilm cells. In addition, qRT-PCR analysis explored the potential inhibitory mechanism of QA against biofilm formation, which indicated that QA significantly repressed the gene sarA and activated the gene agrA. Moreover, QA exhibited a highly ability to reduce the number of sessile S. aureus cells adhered on the stainless steel. So, it was suggested that QA could be used as a promising antibiofilm agent to control biofilm formation of S. aureus.

QA effectively inhibited S. aureus biofilm formation. The key genes of biofilm inhibition induced by QA were agrA and sarA.

A study of antimicrobial activity of polyphenols derived from wood

Due to the spreading and increasing drug resistance of pathogens, the search for novel antibiotics is becoming ever more important. Plant-derived polyphenols are a vast and promising class of compounds with a potential to fight infectious diseases. Still, they are not routinely used in clinical practice. No reports on the in vivo studies of these compounds have been presented. The aim of our work was to compare the antimicrobial activity of resveratrol (stilbene), dihydroquercetin and dihydromyricetin (flavonols) extracted from the bark and wood of conifers against the dermatophytes Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. Using the radial diffusion assay, we established that dihydroquercetin, resveratrol and dihydromyricetin exhibit high activity against S. aureus even at the smallest possible concentrations of 0.22, 0.15, and 0.15 mM, respectively. In contrast, the highest achievable concentrations of these compounds in the solutions (21.5, 15.5 and 15.0 mM for dihydroquercetin, resveratrol and dihydromyricetin, respectively) have no effect on the growth of P. aeruginosa and C. albicans. These findings suggest that polyphenols derived from conifers could have a potential to be used as a medicine for topical application to treat bacterial infections of the skin caused by S. aureus.

Epigenetic modulator UVI5008 inhibits MRSA by interfering with bacterial gyrase

The impact of multi-drug resistant bacterial strains on human health is reaching worrisome levels. Over 2 million people are infected by resistant bacteria, and more than 700,000 people die each year because of the continuous spread of resistant strains. The development of new antibiotics and the prudent use of existing ones to prolong their lifespan require a constant effort by drug industries and healthcare workers. The re-purposing of existing drugs for use as antimicrobial agents would streamline the development of new antibacterial strategies. As part of this effort, we screened a panel of drugs previously characterized to be epigenetic modulators/pro-apoptotic/differentiative drugs. We selected a few compounds that alter Gram-positive growth. Among these, UVI5008, a derivative of the natural compound psammaplin A (Psa_A), was identified. The interaction of Psa_A with the DNA gyrase enzyme has been shown, and here, we hypothesized and confirmed the gyrase-specific activity by biochemical assays. UVI5008 exhibited growth inhibition activity against Staphylococcus aureus via structural modification of the cell wall, which was observed by SEM electron microscopy. Based on our findings, we propose UVI5008 as an alternative antibacterial compound against methicillin-resistant (Met.R) S. aureus strains.

Antibacterial Properties of Medicinal Plants From Pakistan Against Multidrug-Resistant ESKAPE Pathogens

Local people in the Sudhnoti district of Pakistan share a rich practice of traditional medicine for the treatment of a variety of ailments. We selected nine plants from the Sudhnoti ethnopharmacological tradition used for the treatment of infectious and inflammatory disease. Our aim was to evaluate the in vitro anti-infective potential of extracts from these species against multidrug-resistant (MDR) ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa, and Enterobacter species) pathogens. Plant specimens were collected in the Sudhnoti district of Pakistan and vouchers deposited in Pakistan and the USA. Dried bulk specimens were ground into a fine powder and extracted by aqueous decoction and maceration in ethanol. Extracts were assessed for growth inhibitory activity against ESKAPE pathogens and biofilm and quorum sensing activity was assessed in Staphylococcus aureus. Cytotoxicity to human cells was assessed via a lactate dehydrogenase assay of treated human keratinocytes (HaCaTs). Four ethanolic extracts (Zanthoxylum armatum, Adiantum capillus-venaris, Artemisia absinthium, and Martynia annua) inhibited the growth of MDR strains of ESKAPE pathogens (IC₅₀: 256 μg mL^-1). All extracts, with the exception of Pyrus pashia and M. annua, exhibited significant quorum quenching in a reporter strain for S. aureus agr I. The ethanolic extract of Z. armatum fruits (Extract 1290) inhibited quorum sensing (IC₅₀ 32-256 μg mL^-1) in S. aureus reporter strains for agr I-III. The quorum quenching activity of extract 1290 was validated by detection of δ-toxin in the bacterial supernatant, with concentrations of 64-256 μg mL^-1 sufficient to yield a significant drop in δ-toxin production. None of the extracts inhibited S. aureus biofilm formation at sub-inhibitory concentrations for growth. All extracts were well tolerated by human keratinocytes (LD₅₀ ≥ 256 μg mL^-1). Chemical analysis of extract 1290 by liquid chromatography-Fourier transform mass spectrometry (LC-FTMS) revealed the presence of 29 compounds, including eight with putative structural matches. In conclusion, five out of the nine selected anti-infective medicinal plants exhibited growth inhibitory activity against at least one MDR ESKAPE pathogen at concentrations not harmful to human keratinocytes. Furthermore, Z. armatum was identified as a source of quorum quenching natural products and further bioassay-guided fractionation of this species is merited.

Systematic study on active compounds as antibacterial and antibiofilm agent in aging onions

Quantitative investigation and systematic studies of quercetin, total phenolics, flavonoids, antioxidants, antibacterial and antibiofilm or antibiofouling properties of methanolic extracts of onions obtained from six different varieties have been carried out to explore their relative merits in terms of biological activities of fresh and aging onions. Total phenolic content in the extracts was examined spectrophotometrically using Folin–Ciocalteau’s phenol reagent and total antioxidant activity was studied by FRAP and DPPH methods. In vitro antibacterial activity of the extracts was investigated on Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Bacillus cereus) respectively, by using a modified Kirby–Bauer disc diffusion method. Antibiofilm activity was tested by crystal violet assay. The best results against biofilm formation were observed for the extracts obtained from onions stored for three months. The total phenolic and antioxidant content found to be increased upon aging in all the six varieties; red skinned onion (Happyhong) showed the highest level of total phenolics (5110.07 ± 196.56 μg GAEg⁻¹ FW) and total flavonoids (2254.00 ± 154.82 μg QEg⁻¹ FW) after three months. The results showed that in all the varieties, quercetin content as well as biological activity increases with aging in the stored onions compared with the fresh ones.

Antibacterial, antibiofilm and antiquorum sensing effects of Thymus daenensis and Satureja hortensis essential oils against Staphylococcus aureus isolates

AIMS

The present study was conducted to investigate the effects of Thymus daenensis and Satureja hortensis essential oils (EOs) on the planktonic growth, biofilm formation and quorum sensing (QS) of some Staphylococcus aureus isolates (strong biofilm producers).

METHODS AND RESULTS

Minimum inhibitory concentration (MIC) of the EOs, inhibition of biofilm formation as well as disruption of preformed Staph. aureus biofilms were assessed. The antibiofilm activity of the EOs was determined using microtitre plate test (MtP) and scanning electron microscope (SEM). The QS inhibitory activity was also examined on the pregrown biofilms by gene expression analysis using quantitative real-time RT-polymerase chain reaction (PCR) of hld gene (RNAIII transcript). Moreover, tetrazolium-based colorimetric assay (MTT) was performed to detect cytotoxic effects of these EOs on the Vero cell line. Finally, the major components of the tested EOs were determined using Gas Chromatography-Mass Spectrometry (GC-MS). The MICs of T. daenensis and S. hortensis EOs against planktonic cells of the isolates were 0·0625 and 0·125 μl ml^-1 respectively. The minimum bactericidal concentrations for both of the EOs was 0·125 μl ml^-1 . The MtP test showed a significant inhibitory effect of the EOs on the biofilm formation and disruption at sub-MIC concentrations. These results were confirmed by SEM. Real-time PCR revealed a significant down-regulation of hld gene following treatment with MIC/2 concentration of S. hortensis EO. GC-MS analysis showed that carvacrol, terpinene and thymol were the major components of the applied EOs.

CONCLUSIONS

As selected EOs did not show significant cytotoxic effects even up to tenfold of MIC concentration, the applied EOs seem to be good candidates for preventing of biofilm formation of Staph. aureus cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study introduced T. daenensis and S. hortensis EOs as new antibiofilm, and S. hortensis EO as anti-QS herbal agents with natural origin against Staph. aureus.

Kaempferol Inhibits the Primary Attachment Phase of Biofilm Formation in Staphylococcus aureus

The ability to form biofilms on surfaces makes Staphylococcus aureus the main pathogenic factor in implanted medical device infections. The aim of this study was to discover a biofilm inhibitor distinct from the antibiotics used to prevent infections resulting from S. aureus biofilms. Here, we describe kaempferol, a small molecule with anti-biofilm activity that specifically inhibited the formation of S. aureus biofilms. Crystal violet (CV) staining and fluorescence microscopy clearly showed that 64 μg/ml kaempferol inhibited biofilm formation by 80%. Meanwhile, the minimum inhibitory concentration (MIC) and growth curve results indicated that kaempferol had no antibacterial activity against the tested bacterial strain. Kaempferol inhibited the primary attachment phase of biofilm formation, as determined by a fibrinogen-binding assay. Moreover, a fluorescence resonance energy transfer (FRET) assay and quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) analyses revealed that kaempferol reduced the activity of S. aureus sortaseA (SrtA) and the expression of adhesion-related genes. Based on these results, kaempferol provides a starting point for the development of novel anti-biofilm drugs, which may decrease the risk of bacterial drug resistance, to prevent S. aureus biofilm-related infections.

Antimicrobial and antioxidant potential of different solvent extracts of the medicinal plant Geum urbanum L

Many Geum species are known to be rich in biologically active compounds and therefore could be a source of new natural products with pharmacological potential. The medicinal plant Geum urbanum L. is widespread in Bulgaria and has been used in folk medicine. In the present study, the methanol extracts of the roots and aerial parts of G. urbanum and their fractions (petroleum ether, ethyl acetate and n-butanol) were investigated for antibacterial and radical scavenging activity. The ethyl acetate and n-butanol fractions inhibited the growth of Gram-positive pathogenic and opportunistic bacteria from the genus Staphylococcus (MIC EtOAc: 0.078 mg/ml aerial and 0.156 mg/ml roots; MIC n-BuOH: 0.156 mg/ml aerial and 1.25 mg/ml roots) and the species Bacillus cereus stronger than the other extracts and fractions tested (MIC EtOAc: 0.078 mg/ml aerial and 0.156 mg/ml roots; MIC n-BuOH: 0.156 mg/ml aerial and 0.078 mg/ml roots), and showed corresponding radical scavenging activity (EtOAc: EC50 1.5 µg/ml aerial, 0.8 µg/ml roots; n-BuOH: 4.5 µg/ml aerial; 3.7 µg/ml roots). Additionally, their total phenolic content was quantified (% of dry EtOAc fractions of roots 61%, of arial parts 32%; of dry n-BuOH fractions of roots 16%, of arial parts 13%). Seven compounds were isolated and identified spectroscopically from the ethyl acetate extract. Two acetylated ellagic acid rhamnosides were found for the first time in the genus Geum and three others, tormentic acid, niga-ichigoside F1, and 3,3'-di-O-methylellagic acid-4-O-β-D-glucopyranoside, were newly detected for the species G. urbanum. Our results reveal that G. urbanum L. is a perspective medicinal plant and deserves further, more detailed studies.

Inhibitory effects of food additives derived from polyphenols on staphylococcal enterotoxin A production and biofilm formation by Staphylococcus aureus

In this study, we examined the inhibitory effects of 14 food additives derived from polyphenol samples on staphylococcal enterotoxin A (SEA) production and biofilm formation by Staphylococcus aureus. Tannic acid AL (TA), Purephenon 50 W (PP) and Polyphenon 70A (POP) at 0.25 mg/mL and Gravinol®-N (GN), Blackcurrant polyphenol AC10 (BP), and Resveratrol-P5 (RT) at 1.0 mg/mL significantly decreased SEA production by S. aureus C-29 (p < 0.05). TA, GN, BP, and RT significantly inhibited the expression of the sea gene in S. aureus C-29 (p < 0.05), while suppression attempts by PP and POP proved unsuccessful. After result analysis, it can be derived that TA, GN, BP, and RT inhibit the production of SEA. Of the six samples, each one significantly inhibited biofilm formation (p < 0.05). Food additives derived from polyphenols have viability to be used as a means to inhibit the enterotoxin production and control the biofilm formation of foodborne pathogens.

Antimicrobial and Antibiofilm Effects of Human Amniotic/Chorionic Membrane Extract on Streptococcus pneumoniae

Background:Streptococcus pneumoniae colonize the human nasopharynx in the form of biofilms. The biofilms act as bacterial reservoirs and planktonic bacteria from these biofilms can migrate to other sterile anatomical sites to cause pneumonia, otitis media (OM), bacteremia and meningitis. Human amniotic membrane contains numerous growth factors and antimicrobial activity; however, these have not been studied in detail. In this study, we prepared amniotic membrane extract and chorionic membrane extract (AME/CME) and evaluated their antibacterial and antibiofilm activities against S. pneumoniae using an in vitro biofilm model and in vivo OM rat model.

Materials and Methods: The AME/CME were prepared and protein was quantified using DC^TM (detergent compatible) method. The minimum inhibitory concentrations were determined using broth dilution method, and the synergistic effect of AME/CME with Penicillin-streptomycin was detected checkerboard. The in vitro biofilm and in vivo colonization of S. pneumoniae were studied using microtiter plate assay and OM rat model, respectively. The AME/CME-treated biofilms were examined using scanning electron microscope and confocal microscopy. To examine the constituents of AME/CME, we determined the proteins and peptides of AME/CME using tandem mass tag-based quantitative mass spectrometry.

Results: AME/CME treatment significantly (p < 0.05) inhibited S. pneumoniae growth in planktonic form and in biofilms. Combined application of AME/CME and Penicillin-streptomycin solution had a synergistic effect against S. pneumoniae. Biofilms grown with AME/CME were thin, scattered, and unorganized. AME/CME effectively eradicated pre-established pneumococci biofilms and has a bactericidal effect. AME treatment significantly (p < 0.05) reduced bacterial colonization in the rat middle ear. The proteomics analysis revealed that the AME/CME contains hydrolase, ribonuclease, protease, and other antimicrobial proteins and peptides.

Conclusion: AME/CME inhibits S. pneumoniae growth in the planktonic and biofilm states via its antimicrobial proteins and peptides. AME/CME are non-cytotoxic, natural human product; therefore, they may be used alone or with antibiotics to treat S. pneumoniae infections.

The Chemical and Antibacterial Evaluation of St. John's Wort Oil Macerates Used in Kosovar Traditional Medicine

Hypericum perforatum L. (Hypericaceae), or St. John's Wort, is a well-known medicinal herb often associated with the treatment of anxiety and depression. Additionally, an oil macerate (Oleum Hyperici) of its flowering aerial parts is widely used in traditional medicine across the Balkans as a topical wound and ulcer salve. Other studies have shown that Oleum Hyperici reduces both wound size and healing time. Of its active constituents, the naphthodianthrone hypericin and phloroglucinol hyperforin are effective antibacterial compounds against various Gram-positive bacteria. However, hyperforin is unstable with light and heat, and thus should not be present in the light-aged oil macerate. Additionally, hypericin can cause phototoxic skin reactions if ingested or absorbed into the skin. Therefore, the established chemistry presents a paradox for this H. perforatum oil macerate: the hyperforin responsible for the antibacterial bioactivity should degrade in the sunlight as the traditional oil is prepared; alternately, if hypericin is present in established bioactive levels, then the oil macerate should cause photosensitivity, yet none is reported. In this research, various extracts of H. perforatum were compared to traditional oil macerates with regards to chemical composition and antibacterial activity (inhibition of growth, biofilm formation, and quorum sensing) vs. several strains of Staphylococcus aureus in order to better understand this traditional medicine. It was found that four Kosovar-crafted oil macerates were effective at inhibiting biofilm formation (MBIC₅₀ active range of 0.004-0.016% v/v), exhibited moderate inhibition of quorum sensing (QSIC₅₀ active range of 0.064-0.512% v/v), and contained detectable amounts of hyperforin, but not hypericin. Overall, levels of hypericin were much higher in the organic extracts, and these also exhibited more potent growth inhibitory activity. In conclusion, these data confirm that oil macerates employed in traditional treatments of skin infection lack the compound credited with phototoxic reactions in H. perforatum use and exhibit anti-biofilm and modest quorum quenching effects, rather than growth inhibitory properties against S. aureus.

Antibiofilm activity of Vetiveria zizanioides root extract against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading human pathogen responsible for causing chronic clinical manifestation worldwide. In addition to antibiotic resistance genes viz. mecA and vanA, biofilm formation plays a prominent role in the pathogenicity of S. aureus by enhancing its resistance to existing antibiotics. Considering the role of folk medicinal plants in the betterment of human health from the waves of multidrug resistant bacterial infections, the present study was intended to explore the effect of Vetiveria zizanioides root on the biofilm formation of MRSA and its clinical counterparts. V. zizanioides root extract (VREX) showed a concentration-dependent reduction in biofilm formation without hampering the cellular viability of the tested strains. Micrographs of scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) portrayed the devastating impact of VREX on biofilm formation. In addition to antibiofilm activity, VREX suppresses the production of biofilm related phenotypes such as exopolysaccharide, slime and α-hemolysin toxin. Furthermore, variation in FT-IR spectra evidenced the difference in cellular factors of untreated and VREX treated samples. Result of mature biofilm disruption assay and down regulation of genes like fnbA, fnbB, clfA suggested that VREX targets these adhesin genes responsible for initial adherence. GC-MS analysis revealed the presence of sesquiterpenes as a major constituent in VREX. Thus, the data of present study strengthen the ethnobotanical value of V. zizanioides and concludes that VREX contain bioactive molecules that have beneficial effect over the biofilm formation of MRSA and its clinical isolates.

Screening of plants with antimicrobial activity against enterobacteria, Pseudomonas spp. and Staphylococcus spp

AIM

This study screened plants for antibacterial properties against bacteria of medical importance.

MATERIALS & METHODS

60 extracts were obtained from the leaves of ten plants (Jatropha weddelliana, Attalea phalerata, Buchenavia tomentosa, Croton doctoris, Mouriri elliptica, Mascagnia benthamiana, Senna aculeata, Unonopis guatterioides, Allagoptera leucocalyx and Bactris glaucescens) using different extraction methods: A) Ethanol 70°C/72 h; B) Water/5 min/100°C; C) Water/1 h/55°C; D) Water/72 h; E) Hexane/72 h and F) Ethanol 99°C/72 h. Enterobacteria/Pseudomonas and staphylococci reference strains and 201 clinical isolates were used. Primary screening was done using agar well-diffusion assay. MIC/minimum bactericidal concentration and chemical characterization were determined.

RESULTS

Extracts 5F and 3A showed the best MIC/minimum bactericidal concentration against clinical isolates and showed the presence of phenols.

CONCLUSION

The present study demonstrated that Mouriri elliptica and Buchenavia tomentosa were the most active plants against the studied bacteria.

Rhodomyrtus tomentosa Leaf Extract Inhibits Methicillin-Resistant Staphylococcus aureus Adhesion, Invasion, and Intracellular Survival in Human HaCaT Keratinocytes

Methicillin-resistant Staphylococcus aureus (MRSA) has an ability to invade nonprofessional phagocytic cells, resulting in persistent infections and most likely host cell death. Series of our studies have claimed pronounced antibacterial efficacy of Rhodomyrtus tomentosa leaf extract. This study was to further investigate potency of the extract in intracellular killing of human HaCaT keratinocytes. Pretreatment of MRSA with the extract resulted in a remarkable reduction in the bacterial adhesion to HaCaT keratinocytes, compared with untreated control (p < 0.001). In addition, at least 60% inhibition of the bacterial invasion into HaCaT cells was observed. Intracellular killing assay demonstrated that the extract exhibited strong antibacterial activity against intracellular MRSA at nontoxic concentrations (128 mg/L), which may have resulted from the increase in bactericidal activity under phagolysosomal pH. Transmission electron microscopy displayed the effects of the extract on alterations in the bacterial cell morphology with cell lysis. Fluorescence microscopy revealed that the extract decreased MRSA-induced apoptosis in HaCaT cells. In addition, cytotoxicity of HaCaT cells caused by MRSA supernatant was reduced at least 50% by the extract. The potential activities of R. tomentosa extract may be useful in an alternative treatment of MRSA infections in slight acidic compartments, particularly skin infections.

Combating Enhanced Intracellular Survival (Eis)-Mediated Kanamycin Resistance of Mycobacterium tuberculosis by Novel Pyrrolo[1,5-a]pyrazine-Based Eis Inhibitors

Tuberculosis (TB) remains one of the leading causes of mortality worldwide. Hence, the identification of highly effective antitubercular drugs with novel modes of action is crucial. In this paper, we report the discovery and development of pyrrolo[1,5-a]pyrazine-based analogues as highly potent inhibitors of the Mycobacterium tuberculosis (Mtb) acetyltransferase enhanced intracellular survival (Eis), whose up-regulation causes clinically observed resistance to the aminoglycoside (AG) antibiotic kanamycin A (KAN). We performed a structure-activity relationship (SAR) study to optimize these compounds as potent Eis inhibitors both against purified enzyme and in mycobacterial cells. A crystal structure of Eis in complex with one of the most potent inhibitors reveals that the compound is bound to Eis in the AG binding pocket, serving as the structural basis for the SAR. These Eis inhibitors have no observed cytotoxicity to mammalian cells and are promising leads for the development of innovative AG adjuvant therapies against drug-resistant TB.

Combating Enhanced Intracellular Survival (Eis)-Mediated Kanamycin Resistance of Mycobacterium tuberculosis by Novel Pyrrolo[1,5-a]pyrazine-Based Eis Inhibitors

Tuberculosis (TB) remains one of the leading causes of mortality worldwide. Hence, the identification of highly effective antitubercular drugs with novel modes of action is crucial. In this paper, we report the discovery and development of pyrrolo[1,5-a]pyrazine-based analogues as highly potent inhibitors of the Mycobacterium tuberculosis (Mtb) acetyltransferase enhanced intracellular survival (Eis), whose up-regulation causes clinically observed resistance to the aminoglycoside (AG) antibiotic kanamycin A (KAN). We performed a structure-activity relationship (SAR) study to optimize these compounds as potent Eis inhibitors both against purified enzyme and in mycobacterial cells. A crystal structure of Eis in complex with one of the most potent inhibitors reveals that the compound is bound to Eis in the AG binding pocket, serving as the structural basis for the SAR. These Eis inhibitors have no observed cytotoxicity to mammalian cells and are promising leads for the development of innovative AG adjuvant therapies against drug-resistant TB.

Inhibitory effects of flavonoids on biofilm formation by Staphylococcus aureus that overexpresses efflux protein genes

This study evaluated the efficacy of glycone (myricitrin, hesperidin and phloridzin) and aglycone flavonoids (myricetin, hesperetin and phloretin) in inhibiting biofilm formation by Staphylococcus aureus RN4220 and S. aureus SA1199B that overexpress the msrA and norA efflux protein genes, respectively. The minimum inhibitory concentration (MIC) and minimum biofilm inhibitory concentration (MBIC₅₀ - defined as the lowest concentration that resulted in ≥50% inhibition of biofilm formation) of flavonoids were determined using microdilution in broth procedures. The flavonoids showed MIC >1024 μg/mL against S. aureus RN4220 and S. aureus SA1199B; however, these compounds at lower concentrations (1-256 μg/mL) showed inhibitory effects on biofilm formation by these strains. Aglycone flavonoids showed lower MBIC₅₀ values than their respective glycone forms. The lowest MBIC₅₀ values (1 and 4 μg/mL) were observed against S. aureus RN4220. Myricetin, hesperetin and phloretin exhibited biofilm formation inhibition >70% for S. aureus RN4220, and lower biofilm formation inhibition against S. aureus SA1199B. These results indicate that sub-MICs of the tested flavonoids inhibit biofilm formation by S. aureus strains that overexpress efflux protein genes. These effects are more strongly established by aglycone flavonoids.

Identification of Ellagic Acid Rhamnoside as a Bioactive Component of a Complex Botanical Extract with Anti-biofilm Activity

Staphylococcus aureus is a leading cause of hospital-acquired infections. It is listed among the top "serious threats" to human health in the USA, due in large part to rising rates of resistance. Many S. aureus infections are recalcitrant to antibiotic therapy due to their ability to form a biofilm, which acts not only as a physical barrier to antibiotics and the immune system, but results in differences in metabolism that further restricts antibiotic efficacy. Development of a modular strategy to synthesize a library of phenolic glycosides allowed for bioactivity testing and identification of anti-biofilm compounds within an extract of the elmleaf blackberry (Rubus ulmifolius). Two ellagic acid (EA) derivatives, EA xyloside and EA rhamnoside, have been identified as components of the Rubus extract. In addition, EA rhamnoside has been identified as an inhibitor of biofilm formation, with activity comparable to the complex extract 220D-F2 (composed of a mixture of EA glycosides), and confirmed by confocal laser scanning microscopy analyses.

Virulence Inhibitors from Brazilian Peppertree Block Quorum Sensing and Abate Dermonecrosis in Skin Infection Models

Widespread antibiotic resistance is on the rise and current therapies are becoming increasingly limited in both scope and efficacy. Methicillin-resistant Staphylococcus aureus (MRSA) represents a major contributor to this trend. Quorum sensing controlled virulence factors include secreted toxins responsible for extensive damage to host tissues and evasion of the immune system response; they are major contributors to morbidity and mortality. Investigation of botanical folk medicines for wounds and infections led us to study Schinus terebinthifolia (Brazilian Peppertree) as a potential source of virulence inhibitors. Here, we report the inhibitory activity of a flavone rich extract "430D-F5" against all S. aureus accessory gene regulator (agr) alleles in the absence of growth inhibition. Evidence for this activity is supported by its agr-quenching activity (IC50 2-32 μg mL-1) in transcriptional reporters, direct protein outputs (α-hemolysin and δ-toxin), and an in vivo skin challenge model. Importantly, 430D-F5 was well tolerated by human keratinocytes in cell culture and mouse skin in vivo; it also demonstrated significant reduction in dermonecrosis following skin challenge with a virulent strain of MRSA. This study provides an explanation for the anti-infective activity of peppertree remedies and yields insight into the potential utility of non-biocide virulence inhibitors in treating skin infections.

Comparison of Phytochemical Composition and Biological Activities of Rubus ulmifolius Extracts Originating from Four Regions of Tunisia

In the current study, the phenolic composition, antioxidant and antimicrobial activities of extracts from Rubus ulmifolius Schott leaves harvested in four localities (Sejnen, Tabarka, Faija and Ain drahem) in Tunisia were investigated for the first time. Great differences were found for the chemical composition, total phenol contents and biological activities among the evaluated extracts. HPLC analysis of methanolic extracts showed that the dominant compounds were kaempferol 3-O-rutinoside and naringenine. In addition, significant correlations were observed between antioxidant activities and phenolic contents. In fact, leaves collected from Sejnen presented higher total phenol content (53.32 mg GAE/g DW) and antioxidant activities (IC₅₀ = 39.40 mg/l) than the others samples. All extracts showed significant antimicrobial activity against six used bacteria with the inhibition zones diameters and minimal inhibitory concentration values were in the range of 8 - 16 mm and 6.25 - 25 mg/ml, respectively. The highest antimicrobial activities were recorded in Sejnen extract against Gram-positive bacteria.

Antibiofilm Activity of Plant Polyphenols

In the history of human medicine, antibiotics represent epochal examples of medical progress. However, with an approaching antibiotic crisis due to the emergence and extensive spread of antimicrobial resistance among bacterial agents, as well as to increasing number of patients with chronic and recalcitrant bacterial biofilm-associated infections, the naturally occurring molecules may become new sources of antibacterial and antibiofilm drugs for clinical usage. Polyphenols represent a class of plant natural products which are important in plant defense against microbial pathogens. The main focus of the review is on the antibiofilm activities of phenolic compounds against bacteria which play an essential role in medical device biofilm-associated infections. The other, not negligible part of the review is devoted to polyphenols’ activity against bacterial agents that cause dental caries and periodontal disease.

Aroma Profile of Rubus ulmifolius Flowers and Fruits During Different Ontogenetic Phases

The chemical composition of spontaneous volatile emission from Rubus ulmifolius flowers and fruits during different stages of development was evaluated by HS-SPME-GC/MS. In total, 155 chemical compounds were identified accounting 84.6 - 99.4% of whole aroma profile of flowers samples and 92.4 - 96.6% for fruit samples. The main constituents were α-copaene, β-caryophyllene, germacrene D, (E,E)-α-farnesene, 1,7-octadien-3-one,2-methyl-6-methylene, tridecane, (E)-2-hexenol acetate, (E)-3-hexenol acetate and cyperene. The results give a chemotaxonomic contribution to the characterization of the VOCs emitted from flowers and fruits during their ontogenic development.

Anti-Acne Activity of Italian Medicinal Plants Used for Skin Infection

Propionibacterium acnes is implicated in the pathogenesis of acne vulgaris, which impacts >85% of teenagers. Novel therapies are in high demand and an ethnopharmacological approach to discovering new plant sources of anti-acne therapeutics could contribute to filling this void in effective therapies. The aims of our study were two-fold: (1) To determine if species identified in ethnopharmacological field studies as having traditional uses for skin and soft tissue infection (SSTI) exhibit significantly more activity against P. acnes than species with no such reported use; and (2) Chemically characterize active extracts and assess their suitability for future investigation. Extracts of Italian medicinal (for acne and other skin infection) and randomly collected plants and fungi were screened for growth-inhibitory and anti-biofilm activity in P. acnes using broth microdilution methods. Bioactive extracts were chemically characterized by HPLC and examined for cytotoxicity against human keratinocytes (HaCaTs). Following evaluation of 157 extracts from 10 fungi and 58 plants, we identified crude extracts from seven species exhibiting growth inhibitory activity (MICs 64–256 μg mL⁻¹). All active extracts were examined for cytotoxicity against HaCaTs; extracts from one fungal and one plant species were toxic (IC₅₀ 256 μg mL⁻¹). HPLC analysis with chemical standards revealed many of these extracts contained chlorogenic acid, p-coumaric acid, ellagic acid, gallic acid, and tannic acid. In conclusion, species used in traditional medicine for the skin exhibited significantly greater (p < 0.05) growth inhibitory and biofilm eradication activity than random species, supporting the validity of an ethnobotanical approach to identifying new therapeutics. The anti-acne activity of three extracts is reported for the first time: Vitis vinifera leaves, Asphodelus microcarpus leaves, and Vicia sativa aerial parts.

Use of Polyphenolic Compounds in Dermatologic Oncology

Polyphenols are a widely used class of compounds in dermatology. While phenol itself, the most basic member of the phenol family, is chemically synthesized, most polyphenolic compounds are found in plants and form part of their defense mechanism against decomposition. Polyphenolic compounds, which include phenolic acids, flavonoids, stilbenes, and lignans, play an integral role in preventing the attack on plants by bacteria and fungi, as well as serving as cross-links in plant polymers. There is also mounting evidence that polyphenolic compounds play an important role in human health as well. One of the most important benefits, which puts them in the spotlight of current studies, is their antitumor profile. Some of these polyphenolic compounds have already presented promising results in either in vitro or in vivo studies for non-melanoma skin cancer and melanoma. These compounds act on several biomolecular pathways including cell division cycle arrest, autophagy, and apoptosis. Indeed, such natural compounds may be of potential for both preventive and therapeutic fields of cancer. This review evaluates the existing scientific literature in order to provide support for new research opportunities using polyphenolic compounds in oncodermatology.

Baicalein Inhibits Staphylococcus aureus Biofilm Formation and the Quorum Sensing System In Vitro

Biofilm formed by Staphylococcus aureus significantly enhances antibiotic resistance by inhibiting the penetration of antibiotics, resulting in an increasingly serious situation. This study aimed to assess whether baicalein can prevent Staphylococcus aureus biofilm formation and whether it may have synergistic bactericidal effects with antibiotics in vitro. To do this, we used a clinically isolated strain of Staphylococcus aureus 17546 (t037) for biofilm formation. Virulence factors were detected following treatment with baicalein, and the molecular mechanism of its antibiofilm activity was studied. Plate counting, crystal violet staining, and fluorescence microscopy revealed that 32 μg/mL and 64 μg/mL baicalein clearly inhibited 3- and 7-day biofilm formation in vitro. Moreover, colony forming unit count, confocal laser scanning microscopy, and scanning electron microscopy showed that vancomycin (VCM) and baicalein generally enhanced destruction of biofilms, while VCM alone did not. Western blotting and real-time quantitative polymerase chain reaction analyses (RTQ-PCR) confirmed that baicalein treatment reduced staphylococcal enterotoxin A (SEA) and α-hemolysin (hla) levels. Most strikingly, real-time qualitative polymerase chain reaction data demonstrated that 32 μg/mL and 64 μg/mL baicalein downregulated the quorum-sensing system regulators agrA, RNAIII, and sarA, and gene expression of ica, but 16 μg/mL baicalein had no effect. In summary, baicalein inhibited Staphylococcus aureus biofilm formation, destroyed biofilms, increased the permeability of vancomycin, reduced the production of staphylococcal enterotoxin A and α-hemolysin, and inhibited the quorum sensing system. These results support baicalein as a novel drug candidate and an effective treatment strategy for Staphylococcus aureus biofilm-associated infections.

Agents that inhibit bacterial biofilm formation

In the biofilm form, bacteria are more resistant to various antimicrobial treatments. Bacteria in a biofilm can also survive harsh conditions and withstand the host's immune system. Therefore, there is a need for new treatment options to treat biofilm-associated infections. Currently, research is focused on the development of antibiofilm agents that are nontoxic, as it is believed that such molecules will not lead to future drug resistance. In this review, we discuss recent discoveries of antibiofilm agents and different approaches to inhibit/disperse biofilms. These new antibiofilm agents, which contain moieties such as imidazole, phenols, indole, triazole, sulfide, furanone, bromopyrrole, peptides, etc. have the potential to disperse bacterial biofilms in vivo and could positively impact human medicine in the future.

Calcium-chelating alizarin and other anthraquinones inhibit biofilm formation and the hemolytic activity of Staphylococcus aureus

Staphylococcal biofilms are problematic and play a critical role in the persistence of chronic infections because of their abilities to tolerate antimicrobial agents. Thus, the inhibitions of biofilm formation and/or toxin production are viewed as alternative means of controlling Staphylococcus aureus infections. Here, the antibiofilm activities of 560 purified phytochemicals were examined. Alizarin at 10 μg/ml was found to efficiently inhibit biofilm formation by three S. aureus strains and a Staphylococcus epidermidis strain. In addition, two other anthraquinones purpurin and quinalizarin were found to have antibiofilm activity. Binding of Ca²⁺ by alizarin decreased S. aureus biofilm formation and a calcium-specific chelating agent suppressed the effect of calcium. These three anthraquinones also markedly inhibited the hemolytic activity of S. aureus, and in-line with their antibiofilm activities, increased cell aggregation. A chemical structure-activity relationship study revealed that two hydroxyl units at the C-1 and C-2 positions of anthraquinone play important roles in antibiofilm and anti-hemolytic activities. Transcriptional analyses showed that alizarin repressed the α-hemolysin hla gene, biofilm-related genes (psmα, rbf, and spa), and modulated the expressions of cid/lrg genes (the holin/antiholin system). These findings suggest anthraquinones, especially alizarin, are potentially useful for controlling biofilm formation and the virulence of S. aureus.