Antibiofilm Capabilities Research Articles

Mechanical and antibacterial properties of polymethyl methacrylate modified with zinc dimethacrylate

Statement of problemPolymethyl methacrylate (PMMA) has been widely used for denture base resin. However, concerns associated with PMMA, such as poor mechanical strength, high roughness, and porosity promoting microbial adhesion have been voiced; appropriate modification of PMMA denture base resin may improve its clinical application. PurposeThe purpose of this in vitro study was to investigate the effect of zinc dimethacrylate (ZDMA) modification on the mechanical and antibacterial properties of PMMA. Material and methodsZDMA at different mass fractions was mixed into PMMA as the experimental group, and unmodified PMMA was the control group. X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), and the degree of conversion (DC%) were applied for characterization. Mechanical properties were measured with the 3-point bend test (n=10). The Streptococcus mutans biofilm model was used to investigate the antibacterial property by using colony-forming unit counts, metabolic activity, live/dead staining, quantitative real-time PCR (qRT-PCR), and SEM (n=5). The cell counting kit (CCK)-8 test was used to evaluate cytotoxicity. Data were subjected to analysis of variance and the post hoc Tukey honestly significant difference test (α=.05). ResultsSEM-EDS and XRD analysis revealed successful ZDMA incorporation into the PMMA matrix. DC% increased with the mass fraction of ZDMA, and no significant differences in DC% values were found among each tested group (P=.554). ZDMA mass fraction at 1 wt%, 2.5 wt%, and 5 wt% enhanced its mechanical properties, but those at 7.5 wt% and 10 wt% were reduced. The results of antibacterial experiments showed that ZDMA-modified PMMA displayed antibiofilm capabilities. Quantitative real-time PCR indicated that the expression levels of tested genes were significantly suppressed and that CCK-8 test indicated no cytotoxicity. ConclusionsZDMA-modified PMMA exhibited antibacterial properties without its mechanical properties being affected. ZDMA is a potential metal crosslinking monomer for the modification of PMMA denture base resin.

The Chemical Profiling, Docking Study, and Antimicrobial and Antibiofilm Activities of the Endophytic fungi Aspergillus sp. AP5.

Growing data suggest that Aspergillus niger, an endophytic fungus, is a rich source of natural compounds with a wide range of biological properties. This study aimed to examine the antimicrobial and antibiofilm capabilities of the Phragmites australis-derived endophyte against a set of pathogenic bacteria and fungi. The endophytic fungus Aspergillus sp. AP5 was isolated from the leaves of P. australis. The chemical profile of the fungal crude extract was identified by spectroscopic analysis using LC-HRESIMS. The fungal-derived extract was evaluated for its antimicrobial activity towards a set of pathogenic bacterial and fungal strains including Staphylococcus aureus, Pseudomonas aeruginosa, Proteus vulgaris, Klebsiella sp., Candida albicans, and Aspergillus niger. Moreover, antibiofilm activity toward four resistant biofilm-forming bacteria was also evaluated. Additionally, a neural-networking pharmacophore-based visual screening predicted the most probable bioactive compounds in the obtained extract. The AP5-EtOAc extract was found to have potent antibacterial activities against S. aureus, E. coli, and Klebsiella sp., while it exhibited low antibacterial activity toward P. Vulgaris and P. aeruginosa and displayed anticandidal activity. The AP5-EtOAc extract had significant antibiofilm activity in S. aureus, followed by P. aeruginosa. The active metabolites’ antifungal and/or antibacterial activities may be due to targeting the fungal CYP 51 and/or the bacterial Gyr-B.

Cloning, Characterization, and Antibacterial Properties of Endolysin LysE Against Planktonic Cells and Biofilms of Aeromonas hydrophila.

Multidrug-resistant bacteria are emerging as a major global threat to public health. Bacteriophages are an important source of antimicrobial enzymes and could be developed as an alternative antibiotic candidate. This study investigates the antibacterial capacity of the endolysin LysE against Aeromonas hydrophila. The endolysin LysE gene was cloned and expressed in Escherichia coli BL21 (DE3) cells. Purified recombinant LysE proteinwas tested for its antimicrobial activity against A. hydrophila. The study reveals that recombinant LysE protein was highly effective against Gram-negative bacteria when combined with antimicrobials that alter the permeability of the outer membrane. Specifically, the enzyme had the highest muralytic activity at pH 4, and maintained over 50% of the activity at pH 10. Moreover, endolysin displayed more than 50% activity even after 30min of incubation at 100°C. Also, endolysin LysE resulted in one log reduction in CFU/mL in 30min and demonstrated antibiofilm capabilities when combined with EDTA. Interestingly, checkerboard assay showed its synergistic effects in combination with lower concentrations of colistin against A. hydrophila. Additionally, in vitro tests with Channa striatus kidney (CSK) cell lines do not show cytotoxic effects. Taken together, these findings suggest that LysE can be employed with outer membrane permeabilizers to expand the arsenal repertoire against Gram-negative bacteria in the aquaculture, food, and medical industries.

Silver Peroxide Nanoparticles for Combined Antibacterial Sonodynamic and Photothermal Therapy.

Metal peroxide nanoparticles designed to elevate the oxidative stress are considered a promising nanotherapeutics in biomedical applications, including chemotherapy, photodynamic therapy, and bacterial disinfection. However, their lack of specificity towards the therapeutic target can cause toxic side effects to healthy tissues. Here, silver peroxide nanoparticles (Ag2 O2 NPs) capable of controlled reactive oxygen species (ROS) release are synthesized. The release of bactericidal Ag+ ions and ROS is strictly regulated by external stimuli of ultrasound (US) and near-infrared (NIR) light. In vitro and in vivo investigations show that the Ag2 O2 NPs present enhanced antibacterial and antibiofilm capabilities with a killing efficiency >99.9999% in 10min, significantly accelerate multi-drug resistant Staphylococcus aureus infected skin wound closure with excellent cytocompatibility and hemocompatibility. This work not only provides the first paradigm for fabricating silver peroxide nanoparticle but also introduces a highly efficient noninvasive and safe therapeutic modality for combating bacterial infectious diseases.

Novel low-shrinkage-stress bioactive nanocomposite with anti-biofilm and remineralization capabilities to inhibit caries

Background/purposeA common reason for dental composite restoration failure is recurrent caries at the margins. Our objectives were to: (1) develop a novel low-shrinkage-stress, antibacterial and remineralizing resin composite; (2) evaluate the effects of dimethylaminohexadecyl methacrylate (DMAHDM) on mechanical properties, biofilm inhibition, calcium (Ca) and phosphate (P) ion release, degree of conversion, and shrinkage stress on the new low-shrinkage-stress resin composite for the first time.Material and methodsThe resin consisted of urethane dimethacrylate (UDMA) and triethylene glycol divinylbenzyl ether (TEG-DVBE) with high resistance to salivary hydrolytic degradation. Composites were made with 0%–8% of DMAHDM for antibacterial activity, and 20% of nanoparticles of amorphous calcium phosphate (NACP) for remineralization. Mechanical properties and Streptococcus mutans biofilm growth on composites were assessed. Ca and P ion releases, degree of conversion and shrinkage stress were evaluated.ResultsAdding 2–5% DMAHDM and 20% NACP into the low-shrinkage-stress composite did not compromise the mechanical properties (p > 0.05). The incorporation of DMAHDM greatly reduced S. mutans biofilm colony-forming units by 2–5 log and lactic acid production by 7 folds, compared to a commercial composite (p < 0.05). Adding 5% DMAHDM did not compromise the Ca and P ion release. The low-shrinkage-stress composite maintained a high degree of conversion of approximately 70%, while reducing the shrinkage stress by 37%, compared to a commercial control (p < 0.05).ConclusionThe bioactive low-shrinkage-stress composite reduced the polymerization shrinkage stress, without compromising other properties. Increasing the DMAHDM content increased the antibacterial effect in a dose-dependent manner.

Variations in composition and bioactivity of Ocimum basilicum cv ‘Aroma 2’ essential oils

The goal of this paper is to study the seasonal influence on the phytochemical composition and bioactivity of Ocimum basilicum L. cv 'Aroma 2' essential oils (EOs), due to considerable interest of this cultivar for the preparation of sauces. By GC-MS analysis, the chemical profiles of EOs from plants harvested in May and in October, were characterized and biological activities were determined. The phytotoxicity on radish (Raphanus sativus L.), lettuce (Lactuca sativa L.), tomato (Solanum lycopersicum L.), and garden cress (Lepidium sativum L.), the antioxidant and the antibacterial properties (towards Gram-positive and Gram-negative strains) as well as the antibiofilm capability, were evaluated. In addition, the total phenolic content was determined. The chemical composition of the oils was influenced by the season, so that the essential oil from plants harvested in May was mainly composed of linalool (48.1 %), while in the October sample eugenol (76.8 %) was the main constituent. Essential oils did not show significant activity against the germination of tested seeds; instead, the radicle growth was inhibited. Both EOs showed good antioxidant activity with an half maximal inhibitory concentration (IC50) 'Aroma 2' May = 6.1 μg/mL, IC50 'Aroma 2' October = 6.6 μg/mL), comparable to vitamin C (IC50 = 3.0 μg/mL). The total phenolic content, with a value of 484.9 mg/g gallic acid equivalent (GAE), confirmed a high antioxidant activity of 'Aroma 2' October essential oil. The EOs and their major compounds, linalool and eugenol, showed a variable degree activity on the tested bacterial strains, in some cases comparable to tetracycline. Both EOs, at the highest dose tested, demonstrated good inhibitory activity of the biofilm produced by all tested strains, with inhibitory percentages not inferior than 58 %. The test of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was employed to evaluate the effect of the oils on cellular metabolism: Pseudomonas aeruginosa was found to be the most sensitive strain.

Evaluation of resveratrol-doped adhesive with advanced dentin bond durability

ObjectivesThis paper aimed to evaluate the influence of resveratrol-doped adhesive on the durability and antibiofilm capability of dentin bonding. MethodsExperimental adhesives were prepared by incorporating resveratrol into a universal adhesive at concentrations of 0 (control), 0.1, 1, and 10 mg/mL. The microtensile bond strength, fracture modes, and adhesive–dentin interface nanoleakage were assessed after 24 h of water storage, 10,000 times of thermocycling or 1-month of collagenase ageing. Relevant antibiofilm capability on Streptococcus mutans (S. mutans), in situ zymography, degree of conversion, and cytotoxicity of resveratrol-doped adhesives were also determined. ResultsIrrespective of thermocycled or collagenase ageing, the resveratrol-doped adhesive (1 mg/mL) maintained the bond strength and reduced the nanoleakage expression. Meanwhile, the inhibitory ability on endogenous protease activity and S. mutans biofilm formation with acceptable biocompatibility were obtained. ConclusionsThis study suggested that the resveratrol-doped adhesive achieved effective improvement on dentin bond durability and secondary caries management. Clinical significanceThe application of the resveratrol-doped adhesive indicates promising benefits to increase the lifetime of composite restorations.

The anti-biofilm capability of nano-emodin-mediated sonodynamic therapy on multi-species biofilms produced by burn wound bacterial strains

BackgroundManagement of burn wound infections (BWIs) is difficult due to the emergence of multidrug-resistant microorganisms. This study aimed to explore the anti-biofilm efficacy of sonodynamic therapy (SDT) using nano-emodin (N-EMO) against multi-species bacterial biofilms containing Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii. MethodsFollowing synthesis and confirmation of N-EMO as a sonosensitizer, the anti-biofilm efficacy of SDT against multi-species bacterial biofilms was determined using minimum inhibitory concentrations (MIC), minimum biofilm inhibitory concentration (MBIC), and minimal biofilm eradication concentration (MBEC) of N-EMO. The reduction of multi-species bacterial biofilms was then evaluated following the treatments using Log reduction and crystal violet (CV) assays. In addition, the expression profiling of abaI, agrA, and lasI genes using SDT with sub-MIC, sub-MBIC, and sub-MBEC of N-EMO was assessed. ResultsSuccessful synthesis of N-EMO was confirmed through several characterization tests. As the results demonstrated, the MIC value of N-EMO for the multi-species bacterial suspension was 0.15 × 10–4 g/L, as well as, the MBEC value of N-EMO was 2.5 × 10–4 g/L, approximately 4-fold higher than that of MBIC (0.62 × 10–4 g/L). According to the CV assay, there were 57.8 %, 71.0 %, and 81.5 % reduction in the biofilm of multi-species bacterial growth following SDT using 1/128 MBEC, 1/16 MBIC, and 1/2 MIC of N-EMO, respectively. Log reductions analysis demonstrated that 1/2 MIC of N-EMO was more potent in inhibiting the biofilm growth of multi-species test bacteria by 5.725 ± 0.12 (99.9993 %). In this study, N-EMO-mediated SDT could obviously downregulate the gene expression of virulence factors (P < 0.05). The gene expression of lasI, agrA, and abaI were downregulated about 2.5-, 3.6-, and 5.5-fold; and 3.0-, 5.2-, and 7.4-fold following SDT with sub-MBIC and sub-MBEC of N-EMO, respectively. ConclusionThese results highlight the potential of N-EMO-mediated SDT in inhibition of biofilm formation, degradation of formed biofilms, and reduction of virulence factor associated with biofilms of multi-species bacterial biofilms in BWIs.

Development of a polymer-based antimicrobial coating for efficacious urinary catheter protection

This study reports the development of a polymer-based catheter coating to facilitate controlled release of antimicrobial peptides (AMP) to target both planktonic bacteria and biofilm in the urinary catheter environment. Catheter associated urinary tract infection (CAUTI) is a common nosocomial infection among hospitalized patients and is a major reservoir of antimicrobial resistant pathogens. Although silver- or antibiotics-coated catheters have been deployed to minimise CAUTI, the inconsistency and lack of durability in antibacterial properties of these coatings have limited their clinical use. The incorporation of AMPs in catheter coatings has gained interest due to the effective bacteria killing effects of AMPs, with few reports on bacterial resistance development against peptides. This study aims to deploy a novel and potentially cost-effective technique to coat an anhydrous polymeric coating impregnated with AMPs for silicone-based catheters, to overcome limitations in conventional hydrogel-based coatings. Sustained peptide release was achieved with the development of an Ethyl Cellulose (EC): 1-Palmitoyl-2-oleoylphosphatidylcholine (POPC)-based diffusion layer over an AMP-laden Polycaprolactone (PCL)-based layer to control AMP diffusion into the environment over a clinically relevant duration. The ‘AMP-EC-PCL’ coating showed good anti-bacteria performance against uropathogenic Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa for up to 6 days. The coating also showed excellent anti-biofilm capability against green fluorescent protein (GFP)-tagged UTI E. coli. Fifteen centimeter catheter segments of single layer ‘AMP-EC-PCL’-coated catheters showed sustainable AMP release kinetics up to 7 days, where good antibacterial and anti-biofilm activity against E. coli was observed. The full scale ‘AMP-EC-PCL’-coated catheter showed improved mechanical integrity compared to commercial silicone catheters with preservation of the catheter balloon integrity upon expansion. Wound healing studies of the coated PDMS samples in mice models showed a reduction in bacteria concentration as compared to uncoated PDMS, indicating in vivo efficacy potential of the developed catheter coating platform.

The Rhodamine Isothiocyanate Analogue as a Quorum Sensing Inhibitor Has the Potential to Control Microbially-Induced Biofouling.

Quorum sensing inhibitors (QSIs) have been proven to be an innovative approach to interfering with biofilm formation, since this process is regulated by QS signals. However, most studies have focused on single-species biofilm formation, whereas studies of the effects of signal interference on the development of multispecies biofilm, especially in the natural environment, are still lacking. Here we develop and evaluate the anti-biofilm capability of a new QSI (rhodamine isothiocyanate analogue, RIA) in natural seawater. During the experiment, biofilm characteristics, microbial communities/functions and network interactions were monitored at 36, 80, and 180 h, respectively. The results showed that the biomass and 3D structure of the biofilm were significantly different in the presence of the QSI. The expression of genes involved in extracellular polysaccharide synthesis was also downregulated in the QSI-treated group. Dramatic differences in microbial composition, β-diversity and functions between the RIA-treated group and the control group were also observed, especially in the early stage of biofilm development. Furthermore, co-occurrence model analysis showed that RIA reduced the complexity of the microbial network. This study demonstrates that rhodamine isothiocyanate analogue is an efficient QS inhibitor and has potential applications in controlling biofouling caused by multispecies biofilm, especially in the early stage of biofouling formation.

Carbon-dot-loaded CoxNi1\u2212xFe2O4; x\u2009=\u20090.9/SiO2/TiO2 nanocomposite with enhanced photocatalytic and antimicrobial potential: An engineered nanocomposite for wastewater treatment

Water scarcity is now a serious global issue resulting from population growth, water decrease, and pollution. Traditional wastewater treatment plants are insufficient and cannot meet the basic standards of water quality at reasonable cost or processing time. In this paper we report the preparation, characterization and multiple applications of an efficient photocatalytic nanocomposite (CoxNi1−xFe2O4; x = 0.9/SiO2/TiO2/C-dots) synthesized by a layer-by-layer method. Then, the photocatalytic capabilities of the synthesized nanocomposite were extensively-studied against aqueous solutions of chloramine-T trihydrate. In addition, reaction kinetics, degradation mechanism and various parameters affecting the photocatalytic efficiency (nanocomposite dose, chloramine-T initial concentration, and reaction pH) were analyzed in detail. Further, the antimicrobial activities of the prepared nanocomposite were tested and the effect of UV-activation on the antimicrobial abilities of the prepared nanocomposite was analyzed. Finally, a comparison between the antimicrobial abilities of the current nanocomposite and our previously-reported nanocomposite (CoxNi1−xFe2O4; x = 0.9/SiO2/TiO2) had been carried out. Our results revealed that the prepared nanocomposite possessed a high degree of crystallinity, confirmed by XRD, while UV–Vis. recorded an absorption peak at 299 nm. In addition, the prepared nanocomposite possessed BET-surface area of (28.29 ± 0.19 m2/g) with narrow pore size distribution. Moreover, it had semi-spherical morphology, high-purity and an average particle size of (19.0 nm). The photocatalytic degradation efficiency was inversely-proportional to chloramine-T initial concentration and directly proportional to the photocatalyst dose. In addition, basic medium (pH 9) was the best suited for chloramine-T degradation. Moreover, UV-irradiation improved the antimicrobial abilities of the prepared nanocomposite against E. coli, B. cereus, and C. tropicalis after 60 min. The observed antimicrobial abilities (high ZOI, low MIC and more efficient antibiofilm capabilities) were unique compared to our previously-reported nanocomposite. Our work offers significant insights into more efficient water treatment and fosters the ongoing efforts looking at how pollutants degrade the water supply and the disinfection of water-borne pathogenic microorganisms.

Effect of P. kessleri extracts treatment on AgNPs synthesis

In this research work, we reported the impact of changes of alga Parachlorella kessleri (P. kessleri) composition on silver nanoparticles (AgNPs) synthesis. P. kessleri (sample A) and three extracts prepared by different methods (heat treatment (extract C), centrifugation (extract D) and combination of methods (B)) were used for AgNPs synthesis. Synthesized AgNPs were analyzed by UV-vis, FTIR, TEM, SEM and EDX analysis. UV-vis confirmed that AgNPs were synthesized by all extracts but amount of nanoparticles, size and stability differed depending on the extract type. FTIR analysis showed that treatment of extract influenced the presence and amount of the functional groups. We also suggested the functional groups responsible for reduction of Ag+ to Ag0 and for nanoparticles stabilization. All synthesized AgNPs have antibiofilm capability which depends not only on extract type but also on NPs size and amount, apparently factors such gradual release of ions and aggregation also influence antibiofilm activity.

Co-delivery of Diverse Therapeutic Compounds Using PEG–PLGA Nanoparticle Cargo against Drug-Resistant Bacteria: An Improved Anti-biofilm Strategy

Controlling biofilms of bacteria is a challenging aspect because of their drug-resistance potentials against a range of antibiotics, demanding the development of active anti-biofilm agents. Rutin(R), a natural antioxidant, and benzamide(B), a synthetic antibacterial agent, have several pharmacological and antibacterial abilities. Herein, we developed PEG-PLGA NPs that synergistically carried rutin and benzamide as drug candidates, while displaying therapeutic and anti-biofilm functions. These drug delivery NPs were synthesized by the oil-in-water emulsion (O/W) solvent evaporation technique. The obtained NPs were characterized by UV-vis, FT-IR, SEM, TEM, and DLS measurements. Confocal laser scanning microscopy was employed to evaluate theanti-biofilmcapabilities against Staphylococcus aureus and Pseudomonas aeruginosa and further quantified the levels of residual biofilm constituents such as protein and exopolysaccharide (EPS). Drug release experiments showed the controlled release of rutin-benzamide (RB)for several days. Antibacterial analyses showed that the minimum inhibitory concentration (MIC) of NPs was at least two times lower than that of the free drugs. RB-PEG-PLGA NPs revealed that they targeted biofilm-forming bacteria through the disruption of the membrane and biofilm surface and were observed to be nontoxic when tested using human erythrocytes and human cell lines. In vivo evaluations in zebrafish showed that the NPs did not alter the antioxidant functions and histological features of tissues. On the basis of results obtained, it is substantiated that the rutin-benzamide-loaded nanocarrier offers potential anti-biofilm therapy due to its high anti-biofilmactivity and biocompatibility.

Antibacterial and Antibiofilm Potential of Mono-dispersed Stable Copper Oxide Nanoparticles-Streptomycin Nano-drug: Implications for Some Potato Plant Bacterial Pathogen Treatment

The novelty of this work is to estimate the antibacterial and antibiofilm capabilities of the mono-dispersed copper oxide nanoparticles (CuO NPs)-streptomycin nano-drug which synthesized by a cost-effective and eco-friendly gamma irradiation method. The incorporated CuO NPs-streptomycin was fully defined by UV–Vis., XRD, FTIR, HRTEM, DLS, HRSEM and EDX elemental analysis. In vitro antibacterial and antibiofilm activities of CuO NPs-streptomycin were examined towards pathogenic bacteria-causing brown, ring, soft rot and black leg diseases in potato plant. The proposed reaction mechanism regarding the synergistic potential between CuO NPs and streptomycin was estimated. The incorporated CuO NPs-streptomycin displayed an absorption peak at 585.0 nm specific for the Surface Plasmon Resonance. Results achieved from HRTEM, HRSEM and XRD verified the mono-dispersed crystalline character of the fabricated CuO NPs-streptomycin with a common particle size of 20.20 nm. CuO NPs-streptomycin exhibited an encouraging antibacterial activity against Clavibacter michiganensis subsp. sepedonicus (35.50 mm ZOI). Additionally, CuO NPs-streptomycin displayed enhanced biofilm inhibition percentage of about 90.99%, 84.23%, and 83.42% toward C. michiganensis subsp. sepedonicus, Ralstonia solanacearum, and Dickeya solani, respectively. Consequently, according to the prominent characteristics, this research could provide insights for determining dangerous agricultural challenges, potato packaging and processing and new nano-drug formula for invading potato pathogenic bacteria through the cultivation.

Au nanoparticle-decorated aragonite microdumbbells for enhanced antibacterial and anticancer activities

The present work reports the very first hydrothermal synthesis of 100% triclinic phase pure aragonite (A1) with microdumbbell microstructural architecture and Au Nanoparticle-decorated (AuNP-decorated) aragonites (A2, A3 and A4) with spherical, pentagonal/hexagonal and agglomerated AuNP-decorated microdumbbells having triclinic aragonite phase as the major and cubic AuNPs as the minor phase. Even in dark the AuNP-decorated aragonites (especially A2) show efficacies as high 90% against gram-negative e.g., Pseudomonas putida (P. putida) bacteria. Further the AuNP-decorated aragonites (A3) show anti-biofilm capability of as high as about 20% against P. putida. Most importantly the AuNP-decorated aragonites (A3) offer anti-cancer efficacy of as high as 53% while those of A1, A2, and A4 are e.g., 26%, 46% and 37%, respectively. For the very first time, based on detailed investigations, the mechanisms behind such advance antibiofilm and anticancer activities are linked to the generation of excess labile toxic reactive oxygen species (ROS). Thus, these materials show enormous potential as futuristic, multi-functional biomaterials for anti-bacterial, anti-biofilm and anti-cancer applications.

Machine Learning Analyses on Data including Essential Oil Chemical Composition and In Vitro Experimental Antibiofilm Activities against Staphylococcus Species.

Biofilm resistance to antimicrobials is a complex phenomenon, driven not only by genetic mutation induced resistance, but also by means of increased microbial cell density that supports horizontal gene transfer across cells. The prevention of biofilm formation and the treatment of existing biofilms is currently a difficult challenge; therefore, the discovery of new multi-targeted or combinatorial therapies is growing. The development of anti-biofilm agents is considered of major interest and represents a key strategy as non-biocidal molecules are highly valuable to avoid the rapid appearance of escape mutants. Among bacteria, staphylococci are predominant causes of biofilm-associated infections. Staphylococci, especially Staphylococcus aureus (S. aureus) is an extraordinarily versatile pathogen that can survive in hostile environmental conditions, colonize mucous membranes and skin, and can cause severe, non-purulent, toxin-mediated diseases or invasive pyogenic infections in humans. Staphylococcus epidermidis (S. epidermidis) has also emerged as an important opportunistic pathogen in infections associated with medical devices (such as urinary and intravascular catheters, orthopaedic implants, etc.), causing approximately from 30% to 43% of joint prosthesis infections. The scientific community is continuously looking for new agents endowed of anti-biofilm capabilities to fight S. aureus and S epidermidis infections. Interestingly, several reports indicated in vitro efficacy of non-biocidal essential oils (EOs) as promising treatment to reduce bacterial biofilm production and prevent the inducing of drug resistance. In this report were analyzed 89 EOs with the objective of investigating their ability to modulate bacterial biofilm production of different S. aureus and S. epidermidis strains. Results showed the assayed EOs to modulated the biofilm production with unpredictable results for each strain. In particular, many EOs acted mainly as biofilm inhibitors in the case of S. epidermidis strains, while for S. aureus strains, EOs induced either no effect or stimulate biofilm production. In order to elucidate the obtained experimental results, machine learning (ML) algorithms were applied to the EOs’ chemical compositions and the determined associated anti-biofilm potencies. Statistically robust ML models were developed, and their analysis in term of feature importance and partial dependence plots led to indicating those chemical components mainly responsible for biofilm production, inhibition or stimulation for each studied strain, respectively.

Effect of antibacterial lipids on biofilm formation by Streptococcus mutans

Streptococcus mutans is the major cariogenic organism associated with Dental Caries, a widespread chronic disease of the oral cavity (Muras et al. 2018). It is associated with oral biofilm formation, production of organic acids, and has the capacity to out-compete non-cariogenic commensal species (Lemos et al. 2013). Recent studies carried out on fatty acids demonstrated effective antimicrobial activity against S. mutans (Hughes, 2014). This study will evaluate the activity of lipids on S. mutans biofilm formation and proposes that dietary constituents may be used as a natural therapy to maintain oral hygiene. Clinical isolate S. mutans 3014 D5929 was exposed to various concentrations of lipid for 24 h. Crystal violet assay was performed for quantification of biofilm biomass. Fluorescent microscopy using SYTO® 9 and Alexa Fluor® 647-labelled dextran conjugate was performed to visualise biofilm formation pre- and post-exposure to MCO. Biofilm biomass was reduced for all lipid concentrations. Fluorescent microscopy indicated a significant reduction in bacterial cell number and a lack of structural biofilm upon exposure to fatty acid mixtures when compared to control. The research demonstrated that lipid does have S. mutans based antimicrobial and antibiofilm capabilities.

Decrease of growth, biofilm and secreted virulence in opportunistic nosocomial Pseudomonas aeruginosa ATCC 25619 by glycyrrhetinic acid

The present study elucidates the antibiofilm and antivirulent capability of glycyrrhetinic acid (GRA) against Pseudomonas aeruginosa ATCC 25619. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of GRA against P. aeruginosa were found to be 160 μg/mL and 420 μg/mL respectively. In an acclimatization resistance analysis using P. aeruginosa, no resistance towards GRA was observed during the habituation period. Adequate penetration of GRA over the biofilm matrix was proposed with the membrane penetration model assembly constructed with the preformed biofilm exhibited the prospective penetration of GRA above the mature biofilm. Furthermore, GRA resulted in the attenuation of virulence factors such as motility, biofilm formation, pyocyanin secretion, secreted proteases with its sub MIC concentrations. The antibiofilm property of GRA was assessed with the light microscopy and high content screening fluorescent imaging system, which clearly demonstrates, the thickness of P. aeruginosa biofilm was reduced to 11.33 ± 2.08 μm from 39 ± 2.51 μm. Transmission Electron Microscopy (TEM) images depicted the morphological changes in cells such as disaggregation of colonies, cell disruption with loss of intracellular material, cytolytic damage, the process of morphological transformation, bacteriolysis indicating the potential effect of GRA.

Lactobacillus acidophilus Derived Biosurfactant as a Biofilm Inhibitor: A Promising Investigation Using Microfluidic Approach

Background: Biomedical devices and implants are adversely affected by biofilm-associated infections that pose serious public health issues. Biosurfactants (BSs) can combat pathogenic biofilms through their antimicrobial, antibiofilm and antiadhesive capabilities. The objective of our research was to produce biosurfactant (BS) from Lactobacillus acidophilus NCIM 2903 and investigate its antibiofilm, antiadhesive potential using microfluidics strategies by mimicking the micro-environment of biofilm. Methods: Antibiofilm and antiadhesive potential was effectively evaluated using different methods like microfluidics assay, catheter assay, polydimethlysiloxane (PDMS) disc assay. Along with this chemical and physical characteristics of BS were also evaluated. Results: Cell free biosurfactant (CFBS) obtained was found to be effective against biofilm which was validated through the microfluidic (MF) or Lab on Chip (LOC) approach. The potency of CFBS was also evaluated on catheter tubing and PDMS surfaces (representative bioimplants). The efficacy of CFBS was also demonstrated through the reduction in surface tension, interfacial tension, contact angle and low critical micelle concentration. Conclusion: CFBS was found to be a potent antimicrobial and antibiofilm agent. We believe that perhaps this is the first report on demonstrating the inhibiting effect of Lactobacillus spp. derived CFBS against selected bacteria via LOC approach. These findings can be explored to design various BSs based formulations exhibiting antimicrobial, antibiofilm and antiadhesive potential for biomedical applications.

Antimicrobial and anti‐quorum‐sensing properties and paint film usage of novel diazaborine‐based copolymers

AbstractTo meet high hygiene requirements, intensive studies are being carried out on antimicrobial materials. This study reports the synthesis of 3‐((1‐hydroxybenzo[d][1,2,3]diazaborinin‐2(1H)‐yl)sulfonyl)propyl methacrylate (DAZBMA) and its polymer, which is antimicrobial [tested with Staphylococcus aureus (ATCC 25923 and MU 40) and Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10239] on solid surfaces. Antibiofilm capability was tested against MU 40. Although DAZBMA and its polymer show a high quorum‐sensing inhibition property (tested with Chromobacterium violaceum CV 026 and CV 12472 and P. aeruginosa PA01), the lesser antibacterial activity of the polymer was improved by copolymerizing DAZBMA with quaternized 2‐dimethylaminoethyl methacrylate. The paint films containing the prepared copolymer are highly active against all tested bacteria and show an antibiofilm effect against hospital‐acquired multiple‐antibiotic‐resistant MU 40. The novel copolymer can be used in water‐soluble paints to reduce its biofilm production and pathogenicity, especially for paints used in hospitals. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46907.