Antibiofilm activity of lawsone against polymicrobial enterohemorrhagic Escherichia coli O157:H7 and Candida albicans by suppression of curli production and hyphal growth.

BACKGROUND: Most bacteria and fungi form biofilms that attach to living or abiotic surfaces. These biofilms diminish the efficacy of antimicrobial agents and contribute to chronic infections. Furthermore, multispecies biofilms composed of bacteria and fungi are often found at chronic infection sites. PURPOSE: In this study, lawsone (2­hydroxy-1,4-naphthoquinone) and its parent 1,4-naphthoquinone were studied for antimicrobial and antibiofilm activities against single-species and multispecies biofilms of enterohemorrhagic Escherichia coli O157:H7 (EHEC) and Candida albicans. METHODS: Biofilm formation assays, biofilm eradication assays, antimicrobial assays, live cell imaging microscopy, confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), extracellular polymeric substances and indole production, cell surface hydrophilicity assay, cell motility, cell aggregation, hyphal growth, dual species biofilm formation, quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), and toxicity assays on plant seed germination and nematode model were utilized to investigate how lawsone affect biofilm development. RESULTS: Sub-inhibitory concentrations of lawsone (35 µg/ml) significantly inhibited single-and multispecies biofilm development. Lawsone reduced the production of curli and indole, and the swarming motility of EHEC, efficiently inhibited C. albicans cell aggregation and hyphal formation, and increased the cell surface hydrophilicity of C. albicans. Transcriptomic analysis showed that lawsone suppressed the expression of the curli-related genes csgA and csgB in EHEC, and the expression of several hypha- and biofilm-related genes (ALS3, ECE1, HWP1, and UME6) in C. albicans. In addition, lawsone up to 100 µg/ml was nontoxic to the nematode Caenorhabditis elegans and to the seed growth of Brassica rapa and Triticum aestivum. CONCLUSION: These results show that lawsone inhibits dual biofilm development and suggest that it might be useful for controlling bacterial or fungal infections and multispecies biofilms.

Distinct local and brain-wide networks are activated by optogenetic stimulation of neurons specific to each layer of motor cortex.

Primary motor cortex (M1) consists of a stack of interconnected but distinct layers (L1-L6) which affect motor control through large-scale networks. However, the brain-wide functional influence of each layer is poorly understood. We sought to expand our knowledge of these layers' circuitry by combining Cre-driver mouse lines, optogenetics, fMRI, and electrophysiology. Neuronal activities initiated in Drd3 neurons (within L2/3) were mainly confined within M1, while stimulation of Scnn1a, Rbp4, and Ntsr1 neurons (within L4, L5, and L6, respectively) evoked distinct responses in M1 and motor-related subcortical regions, including striatum and motor thalamus. We also found that fMRI responses from targeted stimulations correlated with both local field potentials (LFPs) and spike changes. This study represents a step forward in our understanding of how different layers of primary motor cortex are embedded in brain-wide circuitry.

Inhibition of polymicrobial biofilm formation by saw palmetto oil, lauric acid and myristic acid.

Biofilms are communities of bacteria, fungi or yeasts that form on diverse biotic or abiotic surfaces, and play important roles in pathogenesis and drug resistance. A generic saw palmetto oil inhibited biofilm formation by Staphylococcus aureus, Escherichia coli O157:H7 and fungal Candida albicans without affecting their planktonic cell growth. Two main components of the oil, lauric acid and myristic acid, are responsible for this antibiofilm activity. Their antibiofilm activities were observed in dual-species biofilms as well as three-species biofilms of S. aureus, E. coli O157:H7 and C. albicans. Transcriptomic analysis showed that lauric acid and myristic acid repressed the expressions of haemolysin genes (hla and hld) in S. aureus, several biofilm-related genes (csgAB, fimH and flhD) in E. coli and hypha cell wall gene HWP1 in C. albicans, which supported biofilm inhibition. Also, saw palmetto oil, lauric acid and myristic acid reduced virulence of three microbes in a nematode infection model and exhibited minimal cytotoxicity. Furthermore, combinatorial treatment of fatty acids and antibiotics showed synergistic antibacterial efficacy against S. aureus and E. coli O157:H7. These results demonstrate that saw palmetto oil and its main fatty acids might be useful for controlling bacterial infections as well as multispecies biofilms.

Antibiofilm activities of fatty acids including myristoleic acid against Cutibacterium acnes via reduced cell hydrophobicity.

BACKGROUND: Cutibacterium acnes is a major colonizer and inhabitant of human skin and contributes to the pathogenesis of acne vulgaris. C. acnes either alone or with Staphylococcus aureus, which also inhabits skin, readily forms biofilms that are often tolerant of conventional antibiotics and the host immune system. It was hypothesized that the amphiphilic nature of some fatty acids (FAs) inhibit C. acnes or mixed biofilm formation. PURPOSE: The antibacterial and antibiofilm activities of 24 saturated and unsaturated FAs were investigated against C. acnes as well as a mixture of the bacteria C. acnes and S. aureus. METHODS: Anti-biofilm assays, antimicrobial assays, confocal laser scanning microscopy, scanning electron microscopy, extracellular polymeric substance production, and microbial adherence to hydrocarbon assay were utilized to elucidate how active FAs influence biofilm development. RESULTS: Seventeen FAs at 20 µg/ml inhibited C. acnes biofilm formation by 60-99%. The minimum inhibitory concentrations (MICs) of 20 FAs were ≥ 500 µg/ml but 4 medium-chain FAs had MICs in a range 15 to 200 µg/ml. Interestingly, myristoleic acid inhibited biofilm formation at 1 µg/ml. Myristoleic acid also inhibited the formation of S. aureus and mixed C. acnes/S. aureus biofilms. FAs reduced C. acnes hydrophobicity and we found this was generally correlated with their antibiofilm forming efficacies. Transcriptional analyses showed that myristoleic acid modulates the expression of several biofilm-related genes such as lipase, hyaluronate lyase, and virulence-related genes. CONCLUSION: This study shows myristoleic acid and other FAs inhibit biofilm formation by C. acnes and mixed biofilm formation by C. acnes and S. aureus. Hence, myristoleic acid might be useful for treating or preventing acne and C. acnes associated diseases.

Thalamic Input to Orbitofrontal Cortex Drives Brain-wide, Frequency-Dependent Inhibition Mediated by GABA and Zona Incerta.

Anatomical and behavioral data suggest that the ventrolateral orbitofrontal cortex (VLO), which exhibits extensive connectivity and supports diverse sensory and cognitive processes, may exert global influence over brain activity. However, this hypothesis has never been tested directly. We applied optogenetic fMRI to drive various elements of VLO circuitry while visualizing the whole-brain response. Surprisingly, driving excitatory thalamocortical projections to VLO at low frequencies (5-10 Hz) evoked widespread, bilateral decreases in brain activity spanning multiple cortical and subcortical structures. This pattern was unique to thalamocortical projections, with direct stimulations of neither VLO nor thalamus eliciting such a response. High-frequency stimulations (25-40 Hz) of thalamocortical projections evoked dramatically different-though still far-reaching-responses, in the form of widespread ipsilateral activation. Importantly, decreases in brain activity evoked by low-frequency thalamocortical input were mediated by GABA and activity in zona incerta. These findings identify specific circuit mechanisms underlying VLO control of brain-wide neural activities.

The anti-biofilm and anti-virulence activities of trans-resveratrol and oxyresveratrol against uropathogenic Escherichia coli.

Uropathogenic Escherichia coli (UPEC) is the primary causative agent of urinary tract infections, which are one of the most common infectious disease types in humans. UPEC infections involve bacterial cell adhesion to bladder epithelial cells, and UPEC can also form biofilms on indwelling catheters that are often tolerant to common antibiotics. In this study, the anti-biofilm activities of t-stilbene, stilbestrol, t-resveratrol, oxyresveratrol, ε-viniferin, suffruticosol A, and vitisin A were investigated against UPEC. t-Resveratrol, oxyresveratrol, and ε-viniferin, suffruticosol A, and vitisin A significantly inhibited UPEC biofilm formation at subinhibitory concentrations (10-50 µg ml-1). These findings were supported by observations that t-resveratrol and oxyresveratrol reduced fimbriae production and the swarming motility in UPEC. Furthermore, t-resveratrol and oxyresveratrol markedly diminished the hemagglutinating ability of UPEC, and enhanced UPEC killing by human whole blood. The findings show that t-resveratrol, oxyresveratrol, and resveratrol oligomers warrant further attention as antivirulence strategies against persistent UPEC infections.

Antimicrobial and antibiofilm activities of prenylated flavanones from Macaranga tanarius.

BACKGROUND: The emergence of antibiotic resistant microorganisms presents a worldwide problem that requires novel antibiotic and non-antibiotic strategies, and biofilm formation is a mechanism of drug resistance utilized by diverse microorganisms. The majority of microorganisms live in biofilms that help their survival against starvation, antimicrobial agents, and immunological defense systems. Therefore, it is important novel compounds be identified that inhibit biofilm formation and cell survival without drug resistance. STUDY DESIGN: In this study, the antimicrobial and antibiofilm activities of five prenylated flavanones (Okinawan propolins) isolated from fruits of Macaranga tanarius (L.) were investigated against 14 microorganisms including 10 pathogens. RESULTS: Of these five propolins, propolin D at 5-10 µg/ml significantly inhibited biofilm formation by three Staphylococcus aureus strains, a Staphylococcus epidermidis strain, and a Candida albicans with MICs from 10 to 50 µg/ml, and in C. albicans, propolin D was found to inhibit biofilm formation by reducing cell aggregation and downregulated the expressions of hypha/biofilm-related genes including ECE1 and HWP1. Interestingly, at sub-MIC concentrations (10-50 µg/ml), propolin D significantly inhibited biofilm formation by enterohemorrhagic E. coli O157:H7, uropathogenic E. coli O6:H1, and Acinetobacter baumannii without affecting planktonic cell growth, but did not inhibit biofilm formation by a commensal E. coli K-12 strain, three probiotic Lactobacillus plantarum strains, or two Pseudomonas aeruginosa strains. And, propolin D reduced fimbriae production by E. coli O157:H7 and repressed gene expression of curli fimbriae genes (csgA and csgB). Also, propolin D was minimally toxic in a Caenorhabditis elegans nematode model. CONCLUSION: These findings show that prenylated flavanones, especially propolin D from Macaranga tanarius (Okinawan propolis), should be considered potential candidates for the development of non-toxic antibacterial and antifungal agents against persistent microorganisms.

Inhibition of Biofilm Formation by Candida albicans and Polymicrobial Microorganisms by Nepodin via Hyphal-Growth Suppression.

Candida albicans is an opportunistic pathogenic yeast and is responsible for candidiasis. It readily colonizes host tissues and implant devices, and forms biofilms, which play an important role in pathogenesis and drug resistance. In this study, the antibiofilm, antihyphal, and antivirulence activities of nepodin, isolated from Rumex japonicus roots, were investigated against a fluconazole-resistant C. albicans strain and against polymicrobial-microorganism-biofilm formation. Nepodin effectively inhibited C. albicans biofilm formation without affecting its planktonic cell growth. Also, Rumex-root extract and nepodin both inhibited hyphal growth and cell aggregation of C. albicans. Interestingly, nepodin also showed antibiofilm activities against Candida glabrata, Candida parapsilosis, Staphylococcus aureus, and Acinetobacter baumannii strains and against dual biofilms of C. albicans and S. aureus or A. baumannii but not against Pseudomonas aeruginosa. Transcriptomic analysis performed by RNA-seq and qRT-PCR showed nepodin repressed the expression of several hypha- and biofilm-related genes (ECE1, HGT10, HWP1, and UME6) and increased the expression of several transport genes (CDR4, CDR11, and TPO2), which supported phenotypic changes. Moreover, nepodin reduced C. albicans virulence in a nematode-infection model and exhibited minimal cytotoxicity against the nematode and an animal cell line. These results demonstrate that nepodin and Rumex-root extract might be useful for controlling C. albicans infections and multispecies biofilms.

Nematicidal and insecticidal activities of halogenated indoles.

Parasite death via ion channel activations is the hallmark of anthelmintic and antiparasitic drugs. Glutamate gated chloride channel (GluCl) is a prominent targets for drug selection and design in parasitology. We report several iodine-fluorine based lead activators of GluCl by computational studies and structure-activity relationship analysis. 5-Fluoro-4-iodo-1H-pyrrolo [2, 3-b] pyridine and 5-iodoindole were bioactive hits that displayed in vitro anthelmintic and insecticidal activities against Bursaphelenchus xylophilus, Meloidogyne incognita, and Tenebrio molitor. Two important findings stood out: (i) 5F4IPP induced parasite death, and interacted proficiently with Gln219 amino acid of pentameric GluCl in docking analysis, and (ii) 5-iodoindole appeared to act by forming giant vacuoles in nematodes, which led to a form of non-apoptotic death known as methuosis. The study suggests halogenated-indoles and 1H-pyrrolo [2, 3-b] pyridine derivatives be regarded potential biocides for plant-parasitic nematodes and insects, and warrants further research on the mode of actions, and field investigations.

Antibiofilm activities of norharmane and its derivatives against Escherichia coli O157:H7 and other bacteria.

BACKGROUND: Bacterial biofilms exhibit reduced sensitivity to conventional antibiotics and host defence systems and contribute to the persistence of chronic bacterial infections. HYPOTHESIS: The antibiofilm approach using plant alkaloids provides an alternative to antibiotic strategies. STUDY DESIGN: In this study, the antibiofilm activities of various plant alkaloids were investigated against enterohemorrhagic Escherichia coli O157:H7 and Pseudomonas aeruginosa. In the subsequent investigation, the effects of five norharmane derivatives were investigated. RESULT: Harmaline significantly inhibited biofilm formation by E. coli O157:H7, P. aeruginosa PAO1, P. aeruginosa PA14, and Klebsiella oxytoca, and norharmane (ß-carboline) was found to have antibiofilm activity. It was also found that functional groups at the C-1 and C-7 positions of norharmane could play important roles in its antibiofilm activity. Confocal and electron microscopic observations confirmed biofilm inhibition by harmaline and norharmane, and both reduced fimbriae production and swarming and swimming motilities. Furthermore, harmaline and norharmane attenuated the virulence of E. coli O157:H7 in a Caenorhabditis elegans nematode model. CONCLUSION: These findings strongly suggest that harmaline and norharmane could have potential use in antibiofilm strategy against persistent bacterial infections.

Studying Brain Circuit Function with Dynamic Causal Modeling for Optogenetic fMRI.

Defining the large-scale behavior of brain circuits with cell type specificity is a major goal of neuroscience. However, neuronal circuit diagrams typically draw upon anatomical and electrophysiological measurements acquired in isolation. Consequently, a dynamic and cell-type-specific connectivity map has never been constructed from simultaneous measurements across the brain. Here, we introduce dynamic causal modeling (DCM) for optogenetic fMRI experiments-which uniquely allow cell-type-specific, brain-wide functional measurements-to parameterize the causal relationships among regions of a distributed brain network with cell type specificity. Strikingly, when applied to the brain-wide basal ganglia-thalamocortical network, DCM accurately reproduced the empirically observed time series, and the strongest connections were key connections of optogenetically stimulated pathways. We predict that quantitative and cell-type-specific descriptions of dynamic connectivity, as illustrated here, will empower novel systems-level understanding of neuronal circuit dynamics and facilitate the design of more effective neuromodulation therapies.

Essential Oils and Eugenols Inhibit Biofilm Formation and the Virulence of Escherichia coli O157:H7.

Enterohemorrhagic Escherichia coli O157:H7 (EHEC) has caused foodborne outbreaks worldwide and the bacterium forms antimicrobial-tolerant biofilms. We investigated the abilities of various plant essential oils and their components to inhibit biofilm formation by EHEC. Bay, clove, pimento berry oils and their major common constituent eugenol at 0.005% (v/v) were found to markedly inhibit EHEC biofilm formation without affecting planktonic cell growth. In addition, three other eugenol derivatives isoeugenol, 2-methoxy-4-propylphenol, and 4-ethylguaiacol had antibiofilm activity, indicating that the C-1 hydroxyl unit, the C-2 methoxy unit, and C-4 alkyl or alkane chain on the benzene ring of eugenol play important roles in antibiofilm activity. Interestingly, these essential oils and eugenol did not inhibit biofilm formation by three laboratory E. coli K-12 strains that reduced curli fimbriae production. Transcriptional analysis showed that eugenol down-regulated 17 of 28 genes analysed, including curli genes (csgABDFG), type I fimbriae genes (fimCDH) and ler-controlled toxin genes (espD, escJ, escR, and tir), which are required for biofilm formation and the attachment and effacement phenotype. In addition, biocompatible poly(lactic-co-glycolic acid) coatings containing clove oil or eugenol exhibited efficient biofilm inhibition on solid surfaces. In a Caenorhabditis elegans nematode model, clove oil and eugenol attenuated the virulence of EHEC.

The Effects of Music on Pain: A Meta-Analysis.

BACKGROUND: Numerous meta-analyses have been conducted on the topic of music and pain, with the latest comprehensive study published in 2006. Since that time, more than 70 randomized controlled trials (RCTs) have been published, necessitating a new and comprehensive review. OBJECTIVE: The aim of this meta-analysis was to examine published RCT studies investigating the effect of music on pain. METHODS: The present study included RCTs published between 1995 and 2014. Studies were obtained by searching 12 databases and hand-searching related journals and reference lists. Main outcomes were pain intensity, emotional distress from pain, vital signs, and amount of analgesic intake. Study quality was evaluated according to the Cochrane Collaboration guidelines. RESULTS: Analysis of the 97 included studies revealed that music interventions had statistically significant effects in decreasing pain on 0-10 pain scales (MD = -1.13), other pain scales (SMD = -0.39), emotional distress from pain (MD = -10.83), anesthetic use (SMD = -0.56), opioid intake (SMD = -0.24), non-opioid intake (SMD = -0.54), heart rate (MD = -4.25), systolic blood pressure (MD = -3.34), diastolic blood pressure (MD = -1.18), and respiration rate (MD = -1.46). Subgroup and moderator analyses yielded additional clinically informative outcomes. CONCLUSIONS: Considering all the possible benefits, music interventions may provide an effective complementary approach for the relief of acute, procedural, and cancer/chronic pain in the medical setting.

Combining optogenetic stimulation and fMRI to validate a multivariate dynamical systems model for estimating causal brain interactions.

State-space multivariate dynamical systems (MDS) (Ryali et al. 2011) and other causal estimation models are being increasingly used to identify directed functional interactions between brain regions. However, the validity and accuracy of such methods are poorly understood. Performance evaluation based on computer simulations of small artificial causal networks can address this problem to some extent, but they often involve simplifying assumptions that reduce biological validity of the resulting data. Here, we use a novel approach taking advantage of recently developed optogenetic fMRI (ofMRI) techniques to selectively stimulate brain regions while simultaneously recording high-resolution whole-brain fMRI data. ofMRI allows for a more direct investigation of causal influences from the stimulated site to brain regions activated downstream and is therefore ideal for evaluating causal estimation methods in vivo. We used ofMRI to investigate whether MDS models for fMRI can accurately estimate causal functional interactions between brain regions. Two cohorts of ofMRI data were acquired, one at Stanford University and the University of California Los Angeles (Cohort 1) and the other at the University of North Carolina Chapel Hill (Cohort 2). In each cohort, optical stimulation was delivered to the right primary motor cortex (M1). General linear model analysis revealed prominent downstream thalamic activation in Cohort 1, and caudate-putamen (CPu) activation in Cohort 2. MDS accurately estimated causal interactions from M1 to thalamus and from M1 to CPu in Cohort 1 and Cohort 2, respectively. As predicted, no causal influences were found in the reverse direction. Additional control analyses demonstrated the specificity of causal interactions between stimulated and target sites. Our findings suggest that MDS state-space models can accurately and reliably estimate causal interactions in ofMRI data and further validate their use for estimating causal interactions in fMRI. More generally, our study demonstrates that the combined use of optogenetics and fMRI provides a powerful new tool for evaluating computational methods designed to estimate causal interactions between distributed brain regions.

Frequency-selective control of cortical and subcortical networks by central thalamus.

Central thalamus plays a critical role in forebrain arousal and organized behavior. However, network-level mechanisms that link its activity to brain state remain enigmatic. Here, we combined optogenetics, fMRI, electrophysiology, and video-EEG monitoring to characterize the central thalamus-driven global brain networks responsible for switching brain state. 40 and 100 Hz stimulations of central thalamus caused widespread activation of forebrain, including frontal cortex, sensorimotor cortex, and striatum, and transitioned the brain to a state of arousal in asleep rats. In contrast, 10 Hz stimulation evoked significantly less activation of forebrain, inhibition of sensory cortex, and behavioral arrest. To investigate possible mechanisms underlying the frequency-dependent cortical inhibition, we performed recordings in zona incerta, where 10, but not 40, Hz stimulation evoked spindle-like oscillations. Importantly, suppressing incertal activity during 10 Hz central thalamus stimulation reduced the evoked cortical inhibition. These findings identify key brain-wide dynamics underlying central thalamus arousal regulation.

Coumarins reduce biofilm formation and the virulence of Escherichia coli O157:H7.

E. coli O157:H7 is the most common cause of hemorrhagic colitis, and no effective therapy exists for E. coli O157:H7 infection. Biofilm formation is closely related to E. coli O157:H7 infection and constitutes a mechanism of antimicrobial resistance. Hence, the antibiofilm or antivirulence approach provides an alternative to antibiotic strategies. Coumarin and its derivatives have a broad range of biological effects, and in this study, the antibiofilm activities of nine coumarins were investigated against E. coli O157:H7. Coumarin or umbelliferone at 50µg/ml was found to inhibit biofilm E. coli O157:H7 formation by more than 80% without affecting bacterial growth. Transcriptional analysis showed that coumarins repressed curli genes and motility genes in E. coli O157:H7, and these findings were in-line with observed reductions in fimbriae production, swarming motility, and biofilm formation. In addition, esculetin repressed Shiga-like toxin gene stx2 in E. coli O157:H7 and attenuated its virulence in vivo in the nematode Caenorhabditis elegans. These findings show that coumarins have potential use in antivirulence strategies against persistent E. coli O157:H7 infection.

Ginkgolic acids and Ginkgo biloba extract inhibit Escherichia coli O157:H7 and Staphylococcus aureus biofilm formation.

Infection by enterohemorrhagic Escherichia coli O157:H7 (EHEC) is a worldwide problem, and there is no effective therapy. Biofilm formation is closely related to EHEC infection and is also a mechanism of antimicrobial resistance. Antibiofilm screening of 560 purified phytochemicals against EHEC showed that ginkgolic acids C15:1 and C17:1 at 5µg/ml and Ginkgo biloba extract at 100µg/ml significantly inhibited EHEC biofilm formation on the surfaces of polystyrene and glass, and on nylon membranes. Importantly, at their working concentrations, ginkgolic acids and G. biloba extract did not affect bacterial growth. Transcriptional analyses showed that ginkgolic acid C15:1 repressed curli genes and prophage genes in EHEC, and these findings were in-line with reduced fimbriae production and biofilm reductions. Interestingly, ginkgolic acids and G. biloba extract did not inhibit the biofilm formation of a commensal E. coli K-12 strain. In addition, ginkgolic acids and G. biloba extract inhibited the biofilm formation of three Staphylococcus aureus strains. The findings of this study suggest that plant secondary metabolites represent an important resource for biofilm inhibitors.

Diverse plant extracts and trans-resveratrol inhibit biofilm formation and swarming of Escherichia coli O157:H7.

Infection with enterohemorrhagic Escherichia coli O157:H7 (EHEC) is a worldwide problem. Of the 498 plant extracts screened against EHEC, 16 inhibited the formation of biofilm of EHEC by >85% without inhibiting the growth of planktonic cells, and 14 plant extracts reduced the swarming motility of EHEC. The most active extract, Carex dimorpholepis, decreased swimming and swarming motilities and curli formation. Transcriptional analyses showed that the extract of C. dimorpholepis repressed curli genes, various motility genes, and AI-2 quorum sensing genes, which was corroborated by reduction in the production of fimbria, motility, and biofilm by EHEC. Trans-resveratrol at 10 µg ml(-1) in the extract of C. dimorpholepis was found to be a new anti-biofilm compound against EHEC, but importantly, the extract of C. dimorpholepis and trans-resveratrol did not inhibit the fomation of biofilm in four commensal E. coli strains. Furthermore, the extract of C. dimorpholepis decreased the adhesion of EHEC cells to human epithelial cells without affecting the viability of these cells.

Inhibition of Pseudomonas aeruginosa and Escherichia coli O157:H7 biofilm formation by plant metabolite ε-viniferin.

Pathogenic biofilms are associated with persistent infection due to their high resistances to diverse antibiotics. Pseudomonas aeruginosa infects plants, animals, and humans and is a major cause of nosocomial diseases in patients with cystic fibrosis. In the present study, the antibiofilm abilities of 522 plant extracts against P. aeruginosa PA14 were examined. Three Carex plant extracts at a concentration of 200 µg/mL inhibited P. aeruginosa biofilm formation by >80% without affecting planktonic cell growth. In the most active extract of Carex pumila , resveratrol dimer ε-viniferin was one of the main antibiofilm compounds against P. aeruginosa. Interestingly, ε-viniferin at 10 µg/mL inhibited biofilm formation of enterohemorrhagic Escherichia coli O157:H7 by 98%. Although Carex extracts and trans-resveratrol are known to possess antimicrobial activity, this study is the first to report that C. pumila extract and ε-viniferin have antibiofilm activity against P. aeruginosa and E. coli O157:H7.

Anti-biofilm activities of quercetin and tannic acid against Staphylococcus aureus.

Staphylococcus aureus is a leading cause of nosocomial infections because of its resistance to diverse antibiotics. The formation of a biofilm is one of the mechanisms of drug resistance in S. aureus. The anti-biofilm abilities of 498 plant extracts against S. aureus were examined. Seventy-two plant extracts belonging to 59 genera and 38 families were found to significantly inhibit the formation of biofilms of S. aureus without affecting the growth of planktonic cells. The most active extract, from Alnus japonica, inhibited the formation of biofilms by three S. aureus strains by >70% at 20 µg ml(-1). Transcriptional analyses showed that extract of A. japonica repressed the intercellular adhesion genes icaA and icaD most markedly. Quercetin and tannic acid are major anti-biofilm compounds in the extract of A. japonica. Additionally, the extract of A. japonica and its component compound quercetin, reduced hemolysis by S. aureus. This phenomenon was not observed in the treatment with tannic acid. This study suggests that various plant extracts, such as quercetin and tannic acid, could be used to inhibit the formation of recalcitrant biofilms of S. aureus.