Inhibit Biofilm Growth Research Articles

Endogenous production of 2-phenylethanol by Cunninghamella echinulata inhibits biofilm growth of the fungus

The filamentous fungus Cunninghamella echinulata is a model of mammalian xenobiotic metabolism. Under certain conditions it grows as a biofilm, which is a natural form of immobilisation and enables the fungus to catalyse repeated biotransformations. Putative signalling molecules produced by other Cunninghamella spp., such as 3-hydroxytyrosol and tyrosol, do not affect the biofilm growth of C. echinulata, suggesting that it employs a different molecule to regulate biofilm growth. In this paper we report that 2-phenylethanol is produced in higher concentrations in planktonic cultures of C. echinulata than when the fungus is grown as a biofilm. We demonstrate that exogenously added 2-phenylethanol inhibits biofilm growth of C. echinulata but has no effect on planktonic growth. Furthermore, we show that addition of 2-phenylethanol to established C. echinulata biofilm causes detachment. Therefore, we conclude that this molecule is produced by the fungus to regulate biofilm growth.

Development and Antibacterial Properties of 4-[4-(Anilinomethyl)-3-phenylpyrazol-1-yl]benzoic Acid Derivatives as Fatty Acid Biosynthesis Inhibitors.

A number of novel pyrazole derivatives have been synthesized, and several of these compounds are potent antibacterial agents with minimum inhibitory concentrations as low as 0.5 μg/mL. Human cell lines were tolerant to these lead compounds, and they showed negligible hemolytic effects at high concentrations. These bactericidal compounds are very effective against bacterial growth in both planktonic and biofilm contexts. Various techniques were applied to show the inhibition of biofilm growth and eradication of preformed biofilms by lead compounds. Potent compounds are more effective against persisters than positive controls. In vivo studies revealed that lead compounds are effective in rescuing C. elegans from bacterial infections. Several methods were applied to determine the mode of action including membrane permeability assay and SEM micrograph studies. Furthermore, CRISPRi studies led to the determination of these compounds as fatty acid biosynthesis (FAB) inhibitors.

Gentamicin Eluting 3D-Printed Implants for Preventing Post-Surgical Infections in Bone Fractures.

A surgically implantable device is an inevitable treatment option for millions of people worldwide suffering from diseases arising from orthopedic injuries. A global paradigm shift is currently underway to tailor and personalize replacement or reconstructive joints. Additive manufacturing (AM) has provided dynamic outflow to the customized fabrication of orthopedic implants by enabling need-based design and surface modification possibilities. Surgical grade 316L Stainless Steel (316L SS) is promising with its cost, strength, composition, and corrosion resistance to fabricate 3D implants. This work investigates the possibilities of application of the laser powder bed fusion (L-PBF) technique to fabricate 3D-printed (3DP) implants, which are functionalized with a multilayered antimicrobial coating to treat potential complications arising due to postsurgical infections (PSIs). Postsurgical implant-associated infection is a primary reason for implantation failure and is complicated mainly by bacterial colonization and biofilm formation at the installation site. PLGA (poly-d,l-lactide-co-glycolide), a biodegradable polymer, was utilized to impart multiple layers of coating using the airbrush spray technique on 3DP implant surfaces loaded with gentamicin (GEN). Various PLGA-based polymers were tested to optimize the ideal lactic acid: glycolic acid ratio and molecular weight suited for our investigation. 3D-Printed PLGA-GEN substrates sustained the release of gentamicin from the surface for approximately 6 weeks. The 3DP surface modification with PLGA-GEN facilitated cell adhesion and proliferation compared to control surfaces. The cell viability studies showed that the implants were safe for application. The 3DP PLGA-GEN substrates showed good concentration-dependent antibacterial efficacy against the common PSI pathogen Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). The GEN-loaded substrates demonstrated antimicrobial longevity and showed significant biofilm growth inhibition compared to control. The substrates offered great versatility regarding the in vitro release rates, antimicrobial properties, and biocompatibility studies. These results radiate great potential in future human and veterinary clinical applications pertinent to complications arising from PSIs, focusing on personalized sustained antibiotic delivery.

Epigallocatechin-3-gallate/mineralization precursors co-delivery hollow mesoporous nanosystem for synergistic manipulation of dentin exposure.

As a global public health focus, oral health plays a vital role in facilitating overall health. Defected teeth characterized by exposure of dentin generally increase the risk of aggravating oral diseases. The exposed dentinal tubules provide channels for irritants and bacterial invasion, leading to dentin hypersensitivity and even pulp inflammation. Cariogenic bacterial adhesion and biofilm formation on dentin are responsible for tooth demineralization and caries. It remains a clinical challenge to achieve the integration of tubule occlusion, collagen mineralization, and antibiofilm functions for managing exposed dentin. To address this issue, an epigallocatechin-3-gallate (EGCG) and poly(allylamine)-stabilized amorphous calcium phosphate (PAH-ACP) co-delivery hollow mesoporous silica (HMS) nanosystem (E/PA@HMS) was herein developed. The application of E/PA@HMS effectively occluded the dentinal tubules with acid- and abrasion-resistant stability and inhibited the biofilm formation of Streptococcus mutans. Intrafibrillar mineralization of collagen fibrils and remineralization of demineralized dentin were induced by E/PA@HMS. The odontogenic differentiation and mineralization of dental pulp cells with high biocompatibility were also promoted. Animal experiments showed that E/PA@HMS durably sealed the tubules and inhibited biofilm growth up to 14 days. Thus, the development of the E/PA@HMS nanosystem provides promising benefits for protecting exposed dentin through the coordinated manipulation of dentin caries and hypersensitivity.

Effects of Flavonoids and Phenols from Moringa oleifera Leaf Extracts on Biofilm Processes in Xanthomonas campestris pv. campestris.

Xanthomonas campestris pv. campestris is the causal agent of black rot in crucifers, a plant disease with significant economic impact. Xanthomonadaceae is a large family of Gram-negative bacteria that cause symptoms by blocking water flow in plants by invading the xylem. To accomplish this, the main mechanism the bacteria use to adapt to environmental changes and colonize tissues is biofilm formation. In recent years, growing interest in natural antimicrobial compounds has led to the study of different phytocomplexes derived from plants. In this work, Moringa oleifera was selected, as its leaves are rich in phenols, essential oils, and vitamins that exert antibacterial activity. X. campestris pv. campestris biofilm, one of its major virulence factors, was studied. Biofilm formation and removal were analyzed on abiotic and biotic surfaces with and without M. oleifera leaf extracts. The data from the analysis show that Moringa oleifera leaf extracts and single phenols were able to inhibit biofilm growth on abiotic surfaces, but the activity of the whole phytocomplex was significantly higher compared to that of individual phenols. The effect of Moringa oleifera extracts on cabbage leaves in vivo was also found to be very important, as scanning electron microscopy showed that treatment with the extracts led to clear unblocking of the xylem, implying many advantages for use in black rot control.

Integration of nitrogen-doped carbon dots onto active layer of forward osmosis membrane for highly efficient antibacteria and enhanced membrane performances

Biofouling severely hampered the development of thin-film composite (TFC) forward osmosis (FO) membrane. Herein, novel nitrogen-doped carbon dots (N-C-dots) with fluorescence and long-lived afterglow dual-emission were fabricated using Na2EDTA and urea as co-precursors. The N-C-dots aqueous solution can synchronously produce superoxide anion radical (O2-ˑ) and singlet oxygen (1O2) under light irradiation, exhibiting immense nanoenzyme activities. The membranes (PEI-M and N-C-dots/PEI-M) were prepared by grafting PEI and N-C-dots/polyethyleneimine nanocomposites (N-C-dots/PEI) onto the active layer of pristine TFC FO membrane (Control-M), respectively. The N-C-dots/PEI-M exhibited much better hydrophilicity and smoothness than Control-M and PEI-M, resulting in a higher water permeability. Most significantly, N-C-dots/PEI-M possessed a unique dual-mode biofouling resistance, which responded to the potentials of N-C-dots as oxidase mimic and photosensitizer. In dynamic sewage treatment test, N-C-dots/PEI-M displayed much lower reduction in water flux and much better anti-biofouling behavior. Results above demonstrated that the modification strategy with N-C-dots/PEI is highly effective, pioneering a new horizon for the highly efficient inhibition of biofilm growth and biofouling development under visible light.

Real-Time Impedance-Based Monitoring of the Growth and Inhibition of Osteomyelitis Biofilm Pathogen Staphylococcus aureus Treated with Novel Bisphosphonate-Fluoroquinolone Antimicrobial Conjugates.

Osteomyelitis is a limb- and life-threatening orthopedic infection predominantly caused by Staphylococcus aureus biofilms. Bone infections are extremely challenging to treat clinically. Therefore, we have been designing, synthesizing, and testing novel antibiotic conjugates to target bone infections. This class of conjugates comprises bone-binding bisphosphonates as biochemical vectors for the delivery of antibiotic agents to bone minerals (hydroxyapatite). In the present study, we utilized a real-time impedance-based assay to study the growth of Staphylococcus aureus biofilms over time and to test the antimicrobial efficacy of our novel conjugates on the inhibition of biofilm growth in the presence and absence of hydroxyapatite. We tested early and newer generation quinolone antibiotics (ciprofloxacin, moxifloxacin, sitafloxacin, and nemonoxacin) and several bisphosphonate-conjugated versions of these antibiotics (bisphosphonate-carbamate-sitafloxacin (BCS), bisphosphonate-carbamate-nemonoxacin (BCN), etidronate-carbamate-ciprofloxacin (ECC), and etidronate-carbamate-moxifloxacin (ECX)) and found that they were able to inhibit Staphylococcus aureus biofilms in a dose-dependent manner. Among the conjugates, the greatest antimicrobial efficacy was observed for BCN with an MIC of 1.48 µg/mL. The conjugates demonstrated varying antimicrobial activity depending on the specific antibiotic used for conjugation, the type of bisphosphonate moiety, the chemical conjugation scheme, and the presence or absence of hydroxyapatite. The conjugates designed and tested in this study retained the bone-binding properties of the parent bisphosphonate moiety as confirmed using high-performance liquid chromatography. They also retained the antimicrobial activity of the parent antibiotic in the presence or absence of hydroxyapatite, albeit at lower levels due to the nature of their chemical modification. These findings will aid in the optimization and testing of this novel class of drugs for future applications to pharmacotherapy in osteomyelitis.

Preparation of Laser-Ablated Ag Nanoparticle-MMT Clay-Based Beeswax Antibiofilm Coating.

Unlike other antimicrobial agents, Ag-based composites are stable and currently widely used as broad spectral additives, fighting microbial biofilms and other biological threats. The goal of the present study is to develop a green, multifunctional, and robust antibiofilm water-insoluble coating, inhibiting histamine-producing Lentilactobacillus parabuchneri biofilms. Herein, laser-ablated Ag NPs (L-Ag NPs) were incorporated into and onto a montmorillonite (MMT) surface layer with a simple wet chemical method, provided that the electrostatic interaction between L-Ag NPs and MMT clay led to the formation of L-Ag/MMT nanoantimicrobials (NAMs). The use of MMT support can facilitate handling Ag NPs in industrial applications. The Ag/MMT composite was characterized with transmission electron microscopy (TEM) and scanning electron microscopy (SEM), which confirmed the entrapment of L-Ag NPs into MMT clay. The surface chemical composition was assessed with X-ray photoelectron spectroscopy, proving that Ag NPs were in contact with and deposited onto the surface of MMT. The characteristic L-Ag/MMT band was investigated with UV-vis spectroscopy. Following that, the L-Ag/MMT composite was embedded into a biosafe water-insoluble beeswax agent with a spin coating technique. The antimicrobial ion release kinetic profile of the L-Ag/MMT/beeswax coating through an electrothermal atomic absorption spectroscopy (ETAAS) study supported the controlled release of Ag ions, reaching a plateau at 420 ± 80 nM, which is safe from the point of view of Ag toxicity. Microbial biofilm growth inhibition was assessed with real-time in situ Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) in a flow cell assembly over 32 h. The study was further supported by optical density (OD) measurements and SEM on bacteria incubated in the presence of the L-Ag/MMT/beeswax coating.

Inhibition of biofilm growth of Gram-positive and Gram-negative bacteria on tuned polyurethane nanofibers

Inhibition of biofilm growth of Gram-positive and Gram-negative bacteria on tuned polyurethane nanofibers

Antimicrobial Efficiency of Chitosan and Its Methylated Derivative against Lentilactobacillus parabuchneri Biofilms.

Antimicrobial materials are considered potential alternatives to prevent the development of biofilm-associated contaminations. Concerns regarding synthetic preservatives necessitate the development of innovative and safe natural antimicrobials. In the present study, we discuss the in situ infrared attenuated total reflection spectroscopy (IR-ATR) investigations of the selective antimicrobial efficiency of chitosan in controlling the growth of Lentilactobacillus parabuchneri biofilms. The protonated charges of chitosan were additionally amplified by structural modification via methylation, yielding quaternized derivative TMC (i.e., N, N, N-trimethyl chitosan). To evaluate antimicrobial effectiveness against L. parab. biofilms, IR-ATR spectroscopy provided information on molecular mechanisms and insights into chemical changes during real-time biofilm inhibition studies. The integrated fiberoptic oxygen microsensors enabled monitoring oxygen (O2) concentration gradients within biofilms, thereby confirming the metabolic oxygen depletion dropping from 4.5 to 0.7 mg L-1. IR studies revealed strong electrostatic interactions between chitosan/its water-soluble derivative and bacteria, indicating that a few hours were sufficient to affect biofilm disruption. The significant decrease in the IR bands is related to the characteristic spectral information of amide I, II, III, nucleic acid, and extracellular polymeric matrix (EPS) produced by L. parabuchneri biofilms. Cell clusters of biofilms, microcolonies, and destabilization of the EPS matrix after the addition of biopolymers were visualized using optical microscopy. In addition, scanning electron microscopy (SEM) of biofilms grown on polystyrene and stainless-steel surfaces was used to examine morphological changes, indicating the disintegration of the biofilm matrix into individual cells. Quantification of the total biofilm formation correlated with the CV assay results, indicating cell death and lysis. The electrostatic interactions between chitosan and the bacterial cell wall typically occur between protonated amino groups and negatively charged phospholipids, which promote permeabilization. Biofilm growth inhibition was assessed by a viability assay for a period of 72 h and in the range of low MIC values (varying 0.01-2%). These results support the potential of chitosan and TMC for bacterial growth prevention of the foodborne contaminant L. parabuchneri in the dairy industry and for further implementation in food packaging.

Selective Inhibition of the Periodontal Pathogen Porphyromonas gingivalis by Third-Generation Zafirlukast Derivatives.

Periodontal diseases are inflammatory diseases triggered by pathogenic oral bacterial species, such as Porphyromonas gingivalis. Zafirlukast (ZAF) has displayed antibacterial activity against P. gingivalis. Herein, we report the design, synthesis, and selective antibacterial activity of 14 novel third-generation ZAF derivatives. Two second-generation ZAF derivatives were tested as they were not previously tested against P. gingivalis ATCC 33277. Most third-generation derivatives displayed superior/selective antibacterial activity against P. gingivalis compared to ZAF and its second-generation derivatives. The compounds displayed bactericidal activity against P. gingivalis, inhibited biofilm growth, displayed no hemolytic activity, and displayed less cytotoxicity against mammalian cells than ZAF. The superior/selective antibacterial activity of ZAF derivatives against P. gingivalis, increased safety profile, and inhibition of biofilm growth compared to ZAF indicate that the compounds, especially 21a, 21b, and 24g, show promise as antibacterial agents for future studies to test their potential for preventing and treating P. gingivalis-induced periodontal diseases.

A structure-activity relationship analysis of anthraquinones with antifouling activity against marine biofilm-forming bacteria

Anthraquinones (AQs) are chemical scaffolds that have been used both naturally and synthetically for centuries in the food, pharmaceutical, cosmetic and paint industries. AQs, such as citreorosein and emodin, are common additives in antifouling paints which help prevent the global issue of biofouling. To determine the antifouling potential of a family of structurally related compounds nineteen AQs (1–19), were tested for their microbial growth and biofilm adhesion inhibition activity against three marine biofilm forming bacteria, Vibrio carchariae, Pseudoalteromonas elyakovii and Shewanella putrefaciens. More than three-quarters of the tested AQ compounds exhibited activity against both V. carchariae and P. elyakovii at 10 μg/ml whilst exhibiting low antimicrobial effects. The most active compounds (1, 5, 6, 7, 9, 10, 14, 15, 18, 19) were tested for their minimum inhibitory concentrations (MICs) which highlighted that all the tested compounds were highly effective at inhibiting the biofilm growth of P. elyakovii at a very low concentration of 0.001 μg/ml. The variability in MIC for inhibiting the biofilm growth of V. carchariae was assessed by analysing the structure-activity relationships (SARs) between the AQ compounds, and the key structural features leading to improved biofilm growth inhibition activity are reported. Molecular docking analysis was also performed to assess whether interruption of quorum sensing in V. carchariae could be a possible mode of action for the antifouling activity observed.

Proteomic signatures of synergistic interactions in antimicrobials

Mounting evidence has shown that antimicrobial agents can interfere synergistically with bacterial viability and proliferation when acting together at both the planktonic and biofilm levels without clear underlying molecular mechanisms. Here, multiplexed proteomics by iTRAQ was used to study the interplay between two biocides, the isothiazolone 1,2-benzisothiazolin-3-one (BIT) and the chelating agent disodium ethylenediaminetetraacetic acid (EDTA-2Na), employing the Citrobacter werkmanii as a model system. We first confirmed that these two biocides act synergistically on this bacterial species and then extracted the proteomic profiles of C. werkmanii cells in the presence of BIT, EDTA-2Na, and their combinations. In particular, we identified 43 core proteins that are differentially expressed in all three conditions simultaneously. Meanwhile, we found that these core proteins are consistently up-regulated when these two biocides are present, but not for single biocides, where we found a balanced mix of up- and down-regulation. Meanwhile, most of the deletion mutants of the core DEPs exhibited biofilm growth inhibition under joint biocide action, while their response was very heterogenous, with respect to the wild-type strain. Together, our results show that while BIT and EDTA-2Na act on multiple protein targets, they interact synergistically at the protein level in a very consistent manner. SignificanceOur preliminary experiments have demonstrated that a combination of 1,2-benzisothiazolin-3-one (BIT) and EDTA-2Na shows higher inhibitory effects on planktonic growth and biofilm formation in both C. werkmanii and Staphylococcus aureus than when these two biocides act alone. However, the mechanistic basis of such synergistic interaction is still unknown. Therefore, the key proteins involved in the above-mentioned enhanced antimicrobial synergy were elucidated using multiplexed proteomics analysis by isobaric tags for relative and absolute quantification (iTRAQ). Our results reveal that the joint action of BIT and EDTA-2Na induces consistent protein expression alteration in a set of core proteins of C. werkmanii, which underlies a strong synergistic antimicrobial effect, which increase our understanding of the action modes of BIT and EDTA-2Na as well as their combinations.

Preparation of green luminescent silicon quantum dots by synergistic method for VB12 detection and antimicrobial property research application

The studies on the preparation of high-quality and long-wavelength-emitting silicon quantum dots and their application in biochemical detections have attracted increasing interests from researchers. In particular, the exploration of the effect of SiQDs and their complex in antibacterial and inhibition of biofilm areas, is of great significance to human health. This paper reports the fast synthesis of green-fluorescent SiQDs (TC-SiQDs, QYs=25%, Em=520 nm) with the synergistic effect of thiourea and catechol through microwave-assisted one-step hydrothermal route. Based on internal filtering effect, TC-SiQDs were then successfully employed as selective probes to detect vitamin B12, with detection range at 0.05–30 μM and limit of detection at 50 nM. Thanks to the excellent biocompatibility and fluorescence property of TC-SiQDs, they have been applied in bacterial imaging. The prepared TC-SiQDs also exhibit certain antibacterial ability with their minimum inhibitory concentration (MIC) against Staphylococcus aureus (S. aureus) at 250 μg/mL, but their inhibitory ability is effective to the growth of S. aureus biofilm only when the concentration reaches 1.3 mg/mL. TC-SiQDs-lysozyme complex were prepared, based on the effects of singlet oxygen, charge effect and lysozyme hydrolysis of peptidoglycan in the cell wall, the complex exhibits high inhibiting activity with MIC against S. aureus at 10 μg/mL and exhibits superior inhibition activity against S. aureus biofilm at a concentration of only 62.5 μg/mL. This paper provides good theoretical and practical basis for the synthesis of long-wavelength emission and ultra-bright SiQDs and their applications in detection, antibacterial and biofilm growth inhibition, and other biomedical fields.

Antimicrobial activity of quaternary ammonium salts: structure-activity relationship

Compounds with antimicrobial activity have gained much attention in research due to the outbreak of coronavirus disease 2019 (COVID-19). Quaternary ammonium salts (QASs) are an emerging group of antibacterial agents that are used as disinfectants. Many studies have been carried out involving the applications of QASs as antifouling agents for the inhibition of biofilm growth on medical implants and antibacterials on surfaces and in an aquatic environment. In investigating the antibacterial activity of QASs, we addressed the structure-activity relationship and the physicochemical factors. This review is focused on the fine-tuning of the chemical structures of QASs for their applications as wide antibacterial agents. Graphical abstract

Azithromycin possesses biofilm–inhibitory activity and potentiates non-bactericidal colistin methanesulfonate (CMS) and polymyxin B against Klebsiella pneumonia

Novel antibiotic combinations may act synergistically to inhibit the growth of multidrug-resistant bacterial pathogens but predicting which combination will be successful is difficult, and standard antimicrobial susceptibility testing may not identify important physiological differences between planktonic free-swimming and biofilm-protected surface-attached sessile cells. Using a nominally macrolide-resistant model Klebsiella pneumoniae strain (ATCC 10031) we demonstrate the effectiveness of several macrolides in inhibiting biofilm growth in multi-well plates, and the ability of azithromycin (AZM) to improve the effectiveness of the antibacterial last-agent-of-choice for K. pneumoniae infections, colistin methanesulfonate (CMS), against biofilms. This synergistic action was also seen in biofilm tests of several K. pneumoniae hospital isolates and could also be identified in polymyxin B disc-diffusion assays on azithromycin plates. Our work highlights the complexity of antimicrobial-resistance in bacterial pathogens and the need to test antibiotics with biofilm models where potential synergies might provide new therapeutic opportunities not seen in liquid culture or colony-based assays.

Ecological Effects of Daily Antiseptic Treatment on Microbial Composition of Saliva-Grown Microcosm Biofilms and Selection of Resistant Phenotypes.

Antiseptics are widely used in dental practice and included in numerous over-the-counter oral care products. However, the effects of routine antiseptic use on microbial composition of oral biofilms and on the emergence of resistant phenotypes remain unclear. Microcosm biofilms were inoculated from saliva samples of four donors and cultured in the Amsterdam Active Attachment biofilm model for 3 days. Then, they were treated two times daily with chlorhexidine digluconate (CHX) or cetylpyridinium chloride (CPC) for a period of 7 days. Ecological changes upon these multiple antiseptic treatments were evaluated by semiconductor-based sequencing of bacterial 16S rRNA genes and identification of amplicon sequence variants (ASVs). Furthermore, culture-based approaches were used for colony-forming units (CFU) assay, identification of antiseptic-resistant phenotypes using an agar dilution method, and evaluation of their antibiotic susceptibilities. Both CHX and CPC showed only slight effects on CFU and could not inhibit biofilm growth despite the two times daily treatment for 7 days. Both antiseptics showed significant ecological effects on the microbial compositions of the surviving microbiota, whereby CHX led to enrichment of rather caries-associated saccharolytic taxa and CPC led to enrichment of rather gingivitis-associated proteolytic taxa. Antiseptic-resistant phenotypes were isolated on antiseptic-containing agar plates, which also exhibited phenotypic resistance to various antibiotics. Our results highlight the need for further research into potential detrimental effects of antiseptics on the microbial composition of oral biofilms and on the spread of antimicrobial resistance in the context of their frequent use in oral healthcare.

Изменение физико-химических и культуральных свойств бактерий Azospirillum baldaniorum Sp245 под влиянием некоторых синтетических кумаринов

Due to the small number of studies on the role of coumarins in associative symbiotic relationships, some aspects of the influence of synthetic coumarins on the physicochemical and cultural properties of Azospirillum baldaniorum Sp245 were studied for the first time. To reveal the role of hydroxylation in position 7 of the fused aromatic ring – 1-(2-oxo-2H-chromen-3-yl)butan-1,3-dione, comparative studies of the effect of the original and hydroxylated coumarins on the culture of a model strain of azospirilla were carried out. The survival of bacteria after the addition of coumarins was studied by counting CFU on an agar medium. The biofilm formation activity of the culture was assessed using crystal violet. The change in the surface of bacteria under the action of coumarins was studied by the electrical polarizability of bacterial cells on an ELUS electrooptical analyzer (EloSystemGbR, Germany). The yield and monosaccharide composition of extracellular glycopolymers were studied using gas-liquid chromatography.For the first time, an increase in the yield of EPS of bacteria during growth in the presence of 1-(7-hydroxy-2-oxo-2Hchromen-3-yl)butan-1,3-dione by 1.2 and 1.7 times for concentrations of 50 and 100 μM respectively was observed. It has been established for the first time that the hydroxylated substance has a higher antibacterial activity compared to the unsubstituted one. A decrease in the number of viable cells in planktonic culture and inhibition of biofilm growth were revealed. It has been shown by electro-optical analysis that the presence of coumarins in the cultivation medium in all concentrations studied leads to a change in the electrical polarizability of A. baldaniorum Sp245 cells. The use of electrooptical analysis of cell suspensions using monospecific antibodies obtained against lipopolysaccharides of this strain made it possible to reveal the absence of changes in carbohydrate antigenic determinants on the surface of bacterial cells. This is consistent with the data of the analysis of the composition of extracellular polysaccharides by GLC, during which no differences were found in the qualitative composition and ratio of monosaccharides. An increase in the yield of bacterial EPS during growth in the presence of 1-(7-hydroxy-2-oxo-2H-chromen-3-yl) butan-1,3-dione by 1.2 and 1.7 times for concentrations of 50 and 100 μM was shown. The results obtained allow us to consider the changes that have occurred as features of the adaptation of bacteria to the associative conditions of existence.

Chemical composition, antibiofilm, cytotoxic, and anti-acetylcholinesterase activities of Myrtus communis L. leaves essential oil

BackgroundThe potential of essential oils (EOs) and of their principal constituents for eradication of biofilm and at the same time the research of new potential acetylcholinesterase inhibitors is gaining increasing interest in last years. The aims of this study were to determine the chemical composition and to evaluate the antibacterial, cytotoxic, and anti-acetylcholinesterase properties of Myrtus communis leaves essential oil and its main constituents.MethodsEssential oil was obtained by hydrodistillation of M. communis L. leaves and was analyzed by GC and GC–MS. The antimicrobial activity was carried out against both gram-negative and gram-positive bacteria. The microdilution method was used to estimate the minimum inhibitory concentrations (MICs). Then, the capacity of essential oil and its main constituent to inhibit biofilm growth, with the method of O’Toole and Kolterand, and the metabolic activity of biofilm cells through the MTT colorimetric method were evaluated at different times. Moreover, was studied the potential cytotoxic activity against SH-SY5Y cell line with MTT assay and the anti-acetylcholinesterase activity using Ellman’s assay.ResultsMyrtenyl-acetate, 1,8 cineole, α-pinene, and linalool were the main components in the EO. The myrtle EO, at the minimum tested dose (0.4 mg/ml), inhibited S. aureus biofilm by 42.1% and was capable of inhibiting the biofilm cell metabolism in all tested strains, except Staphylococcus aureus. Moreover, the EO showed good cytotoxic and anti-acetylcholinesterase activities IC50 of 209.1 and 32.8 μg/ml, respectively.ConclusionsThe results suggest that myrtle EO and its main constituents could be used as possible products that could act against the resistant pathogenic species E. coli, P. aeruginosa, L. monocytogenes and S. aureus, on the other hand, as possible coadjutants in the treatment of neurological diseases.

Controlling Listeria monocytogenes Growth and Biofilm Formation Using Flavonoids

The aim of this study was to investigate the ability of natural plant-derivate products (flavonoid compounds) to inhibit the growth and biofilm-forming ability of Listeria monocytogenes. A collection of 500 synthetic and natural flavonoids were tested individually on strains of L. monocytogenes for their antimicrobial and antibiofilm activity. The flavonoids were tested against a L. monocytogenes cocktail of five strains at a concentration of 100 μM to determine their effect on planktonic growth. The optical density was measured every hour for 24 h at 37°C, and every hour for 48 h at 22°C. A total of 17 flavonoids were chosen for further study because of their ability to significantly reduce the growth of L. monocytogenes up to 97%. An additional two flavonoids that increased planktonic growth were chosen as well to investigate whether they had the same effect on biofilm growth. A lower concentration of flavonoid compounds (50 μM) was selected to investigate the individual effects on L. monocytogenes biofilm formation using (i) stainless steel coupons to quantify biomass using crystal violet staining and (ii) glass slides using confocal laser scanning microscopic (CLSM) imaging to observe the biofilm architecture. The 19 flavonoids showed various levels of L. monocytogenes biofilm growth inhibition, ranging from 2 to 100% after 48 h of incubation at 22 or 10°C. This includes 18 of the 19 flavonoids significantly (P ≤ 0.05) inhibiting L. monocytogenes biofilm formation on stainless steel coupons under at least one of the testing conditions. However, only one flavonoid compound demonstrated significant biofilm inhibition (P ≤ 0.05) under all conditions tested. Furthermore, 8 of the selected 19 flavonoid compounds showed visible reductions through CLSM in L. monocytogenes biofilm formation. Overall, we identified five flavonoid compounds to be promising antibiofilm and antimicrobial agents against L. monocytogenes.