Biofilm Bacteria Research Articles

High antipersister activity of a promising new quinolone drug candidate in eradicating uropathogenic Escherichia coli persisters and persistent infection in mice.

To develop more potent drugs that eradicate persister bacteria and cure persistent urinary tract infections (rUTIs). We synthesized eight novel clinifloxacin analogs and measured minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), the time-kill curves in uropathogenic Escherichia coli (UPEC) UTI89, and applied the candidate drugs and combinations against biofilm bacteria in vitro and in mice. Transcriptomic analysis was performed for UPEC after candidate drug treatment to shed light on potential mechanism of action. We identified Compound 2, named Qingdafloxacin (QDF), which was more potent than clinafloxacin and clinically used levofloxacin and moxifloxacin, with an MIC of<0.04μg ml-1 and an MBC of 0.08∼0.16μg ml-1. In drug combination studies, QDF+gentamicin+nitrofuran combination but not single drugs completely eradicated all stationary phase bacteria containing persisters and biofilm bacteria, and all bacteria in a persistent UTI mouse model. Transcriptome analysis revealed that the unique antipersister activity of QDF was associated with downregulation of genes involved in bacterial stress response, DNA repair, protein misfolding repair, pyrimidine metabolism, glutamate, and glutathione metabolism, and efflux. QDF has high antipersister activity and its drug combinations proved highly effective against biofilm bacteria in vitro and persistent UTIs in mice, which may have implications for treating rUTIs.

Transcriptomic analysis of biofilm formation by Bacillus cereus under different carbon source conditions

Abstract Background Previous studies found differences in the utilization of different carbon sources during biofilm formation by Bacillus cereus. Illumina HiSeq high-throughput sequencing technology was used to investigate the changes in gene transcript levels in Bacillus cereus biofilm bacteria under different carbon source conditions. Results Compared with the control group, the number of differentially expressed genes in the glucose, maltose, lactose, and skim milk-supplemented groups was 351, 1136, 133, and 487, respectively. The results showed that the pathways involved in the differentially expressed genes were mainly distributed in glycolysis and pentose phosphate pathway, tricarboxylic acid cycle, amino acid metabolism, and fatty acid metabolism. The gene expression of enzymes related to acetoin synthesis from pyruvate was mostly upregulated in the glucose-supplemented group. The gene expression of enzymes related to pyruvate synthesis of branched-chain amino acids in the maltose-supplemented group was mostly upregulated. In the lactose-supplemented group, the gene expression of acetoin biosynthesis from pyruvate was upregulated. Pyruvate production through glycolysis pathway increased in the skim milk-supplemented group, but the metabolic capacity of the tricarboxylic acid cycle did not change significantly. Conclusion The content of pyruvate stored by Bacillus cereus biofilm bacteria through glycolysis or pentose phosphate pathway increased, but the carbon flux into the tricarboxylic acid cycle did not increase, which suggested that carbon fluxes in the extracellular polysaccharide synthesis pathway of the biofilm may be increased, resulting in increased biofilm biomass formation.

Dual functions: A coumarin-chalcone conjugate inhibits cyclic-di-GMP and quorum-sensing signaling to reduce biofilm formation and virulence of pathogens.

Antibiotic resistance or tolerance of pathogens is one of the most serious global public health threats. Bacteria in biofilms show extreme tolerance to almost all antibiotic classes. Thus, use of antibiofilm drugs without bacterial-killing effects is one of the strategies to combat antibiotic tolerance. In this study, we discovered a coumarin-chalcone conjugate C9, which can inhibit the biofilm formation of three common pathogens that cause nosocomial infections, namely, Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli, with the best antibiofilm activity against P. aeruginosa. Further investigations indicate that C9 decreases the synthesis of the key biofilm matrix exopolysaccharide Psl and bacterial second messenger cyclic-di-GMP. Meanwhile, C9 can interfere with the regulation of the quorum sensing (QS) system to reduce the virulence of P. aeruginosa. C9 treatment enhances the sensitivity of biofilm to several antibiotics and reduces the survival rate of P. aeruginosa under starvation or oxidative stress conditions, indicating its excellent potential for use as an antibiofilm-forming and anti-QS drug.

Synthesis, in Silico Study and Biological Evaluation of N-(Benzothiazol/Thiazol-2-yl)benzamide Derivatives as Quorum Sensing Inhibitors against Pseudomonas aeruginosa.

The development of bacterial resistance to chemical therapy poses a severe danger to efficacy of treating bacterial infections. One of the key factors for resistance to antimicrobial medications is growth of bacteria in biofilm. Quorum sensing (QS) inhibition was created as an alternative treatment by developing novel anti-biofilm medicines. Cell-cell communication is impeded by QS inhibition, which targets QS signaling pathway. The goal of this work is to develop newer drugs that are effective against Pseudomonas aeruginosa by decreasing QS and acting as anti-biofilm agents. In this investigation, N-(benzo[d]thiazol-2-yl)benzamide/N-(thiazol-2-yl)benzamide derivatives 3a-h were designed and synthesized in good yields. Further, molecular docking analyses revealed that binding affinity values were founded -11.2 to -7.6 kcal/mol that were moderate to good. The physicochemical properties of these prepared compounds were investigated through in-silico method. Molecular dynamic simulation was also used to know better understanding of stability of the protein and ligand complex. Comparing N-(benzo[d]thiazol-2-yl)benzamide 3a to salicylic acid (4.40±0.10) that was utilised as standard for quorum sensing inhibitor, the anti-QS action was found greater for N-(benzo[d]thiazol-2-yl)benzamide 3a (4.67±0.45) than salicylic acid (4.40±0.10). Overall, research results suggested that N-(benzo[d]thiazol-2-yl)benzamide/N-(thiazol-2-yl)benzamide derivatives 3a-h may hold to develop new quorum sensing inhibitors.

Review on Anti-Biofilm Potential of CRISPR-Cas System on Various Pathogens

The development of bacterial biofilms entails regulatory as well as signalling mechanisms that regulate the shift from a mobile to astationary state of existence, the production of the extracellular polymeric matrix, and the progression of 3-dimensional biofilm formation withemphasis on how easily they may be created and how crucial they are in biological, ecological, and industrial settings, biofilms are the subject ofextensive research. Biofilms and a variety of pathogenic human disorders are frequently linked. Since bacteria in biofilms can resist antibiotics, theimmune system, and other treatments, biofilm infections are typically long-lasting. Many prokaryotes include CRISPR-associated proteins (Cas), a solidadaptable immunological system that may be programmed to damage the bacterial genomes and induce cell death. Short palindromic repeats that aregrouped and adequately spaced together make up CRISPR-Cas. In light of this, CRISPR-Cas can be seen as an exciting strategy to address andovercome antibiotic resistance. Furthermore, the CRISPR-Cas system can create "precise antimicrobials" that target bacterial infections according tospecific DNA sequences. This CRISPR-Cas technique is susceptible to drug-resistant microorganisms due to its selective targeting of the genesinvolved in biofilm formation, pathogenicity, and antibiotic resistance. However, this method requires potent vectors for the CRISPR-Cas system toaccess the bacterial genomes. As vectors, genetically engineered Phage, liposomes, and lipid-mediated nanoparticles are exciting options. Thistechnique has been used to prevent extracellular and intracellular from forming biofilms. The most current developments in creating innovations andpossible advantages of the various CRISPR-Cas delivery methods for the deliberate eradication of bacterial pathogens will be covered in this review,focussing mainly on the anti-biofilm potential, which is found to be one of the primary causes of the difficulty of irradiation of Multi-drug resistantbacteria. Additionally, each distribution system's positive aspects are highlighted, along with its challenges and potential for advancement in the future.

Interactions between Bacteria and Aspergillus fumigatus in Airways: From the Mycobiome to Molecular Interactions.

Interactions between different kingdoms of microorganisms in humans are common but not well described. A recent analysis of the mycobiome has described the presence of different fungi and their positive and/or negative interactions with bacteria and other fungi. In chronic respiratory diseases, these different microorganisms form mixed biofilms to live inside. The interactions between Gram-negative bacteria and filamentous fungi in these biofilms have attracted more attention recently. In this review, we analyse the microbiota of the respiratory tract of healthy individuals and patients with chronic respiratory disease. Additionally, we describe the regulatory mechanisms that rule the mixed biofilms of Aspergillus fumigatus and Gram-negative bacteria and the effects of this biofilm on clinical presentations.

Prospects for Application of Guanidine-Containing Organomineral Complexes as Biocidal Functional Additives for Waterborne Polymer Materials

The possibility of using organomineral complexes of polyhexamethylene guanidine hydrochloride as a functional additive for a waterborne paint based on polyvinyl acetate has been investigated. Organomineral complexes containing 20 and 30 wt % guanidine polymer have been obtained, with intercalation of polyguanidine chains into the interlayer space of montmorillonite being observed. It has been revealed that the stability of the polymer film to water is retained when organomineral complexes are introduced into a polyvinyl acetate dispersion, whereas the water resistance of the film sharply decreases when free polyguanidine is added. There was no significant influence of organomineral complexes on the rheological characteristics of the dispersion and its sedimentation stability. Testing of waterborne paints with various additives has shown that introduction of organomineral complexes into the material prevents the coating from fouling by biofilms of gram-positive bacteria Staphylococcus aureus and Rhodococcus erythropolis, with the hardness, water resistance, and water-vapor transmission of the coatings being retained at a satisfactory level.

Antibacterial Activity of Green Synthesized Silver Nanoparticle using Banana Flower Extract

In recent years, due to unique physical and chemical properties of nanoparticles, its uses to disrupt biofilm of bacteria are revolutionary steps in antimicrobial research. To use in bioprocess the silver nanoparticles should be biocompatible and free from toxic chemicals. In the present study we report a cost effective and environment friendly route for green synthesis of silver nanoparticles using banana flower extract (BFE) as reducing as well as capping agent. This plant has been opted for the present study for its known medicinal properties and it is easily available. The biosynthesized silver nanoparticles are characterized by UV–Vis spectroscopy which showed a broad peak at around 450 nm, indicated the stability of synthesized silver nanoparticles. Antimicrobial potential of silver nanoparticles synthesized were tested against both Gram positive and Gram-negative bacteria. It was found to be effective against both of them and it showed maximum activity against Gram positive bacteria S. aureus. Silver nanoparticles (AgNPs) have been imposed as an excellent antimicrobial agent being able to combat bacteria in vitro and in vivo causing infections. The results show green synthesized silver nanoparticles, using BFE extract, have a potential to inhibit the growth of bacteria.

Antimicrobial photodynamic therapy with erythrosine and blue light on dental biofilm bacteria: study protocol for randomised clinical trial

IntroductionThe objective is to investigate the effect of antimicrobial photodynamic therapy (aPDT) mediated by erythrosine and a blue light-emitting diode (LED) in the reduction of bacteria in dental biofilm.Methods and...

Surface charge adaptive nitric oxide nanogenerator for enhanced photothermal eradication of drug-resistant biofilm infections.

Due to protection of extracellular polymeric substances, the therapeutic efficiency of conventional antimicrobial agents is often impeded by their poor infiltration and accumulation in biofilm. Herein, one type of surface charge adaptable nitric oxide (NO) nanogenerator was developed for biofilm permeation, retention and eradication. This nanogenerator (PDG@Au-NO/PBAM) is composed of a core-shell structure: thermo-sensitive NO donor conjugated AuNPs on cationic poly(dopamine-co-glucosamine) nanoparticle (PDG@Au-NO) served as core, and anionic phenylboronic acid-acryloylmorpholine (PBAM) copolymer was employed as a shell. The NO nanogenerator featured long circulation and good biocompatibility. Once the nanogenerator reached acidic biofilm, its surface charge would be switched to positive after shell dissociation and cationic core exposure, which was conducive for the nanogenerator to infiltrate and accumulate in the depth of biofilm. In addition, the nanogenerator could sustainably generate NO to disturb the integrity of biofilm at physiological temperature, then generate hyperthermia and explosive NO release upon NIR irradiation to efficiently eradicate drug-resistant bacteria biofilm. Such rational design offers a promising approach for developing nanosystems against biofilm-associated infections.

Synergy of Antibiotics and Antibiofilm Agents against Methicillin-Resistant Staphylococcus aureus Biofilms.

Methicillin-resistant Staphylococcus aureus (MRSA) infections are some of the most common antibiotic-resistant infections, often exacerbated by the formation of biofilms. Here, we evaluated six compounds, three common antibiotics used against MRSA and three antibiofilm compounds, in nine combinations to investigate the mechanisms of synergistic eradication of MRSA biofilms. Using metabolic assessment, colony enumeration, confocal fluorescence microscopy, and scanning electron microscopy, we identified two promising combinations of antibiotics with antibiofilm agents against preformed MRSA biofilms. The broad-spectrum protease, proteinase K, and membrane-targeting antibiotic, daptomycin, worked in synergy against MRSA biofilms by manipulating the protein content, increasing access to the cell membrane of biofilm bacteria. We also found that the combination of cationic peptide, IDR-1018, with the cell wall cross-linking inhibitor, vancomycin, exhibited synergy against MRSA biofilms by causing bacterial damage and preventing repair. Our findings identify synergistic combinations of antibiotics and antibiofilm agents, providing insight into mechanisms that may be explored further for the development of effective treatments against MRSA biofilm.

Coupling of submerged macrophytes and epiphytic biofilms reduced methane emissions from wetlands: Evidenced by an antibiotic inhibition experiment

Wetlands are the largest natural methane source, but how submerged macrophytes affect methane emission remains controversial. In this study, the impacts of submerged macrophytes on methane fluxes, water purification, and epiphytic microbial community dynamics were investigated in simulated wetlands (with and without Hydrilla verticillata) treated with norfloxacin (NOR) for 24 days. Mean methane fluxes were significantly lower in treatments with Hydrilla verticillata (56.84–90.94 mg/m2/h) than bulks (65.96–113.21 mg/m2/h) (p < 0.05) during the experiment regardless of NOR. The relative conductivity (REC) values, H2O2, and malondialdehyde (MDA) contents increased in plant leaves, while water nutrients removal rates decreased with increasing NOR concentration at the same sampling time. The partial least squares path model analysis revealed that plant physiological indices and water nutrients positively affected methane fluxes (0.72 and 0.49, p < 0.001). According to illumina sequencing results of 16S rRNA and pmoA genes, α-proteobacteria (type II) and γ-proteobacteria (type I) were the dominant methanotroph classes in all epiphytic biofilms. The ratio of type I/type II methanotrophs and pmoA gene abundance in epiphytic biofilm was considerably lower in treatment with 16 mg/L NOR than without it (p < 0.05). pmoA gene abundance was negatively correlated with methane fluxes (p < 0.05). Additionally, the assembly of epiphytic bacterial community was mainly governed by deterministic processes, while stochastic dispersal limitation was the primary assembly process in the epiphytic methanotrophic community under NOR stress. The deterministic process gained more importance with time both in bacterial and methanotrophic community assembly. Network analysis revealed that relationships among bacteria in epiphytic biofilms weakened with time but associations among methanotrophic members were enhanced under NOR stress over time. It could be concluded that submerged macrophytes-epiphytic biofilms symbiotic system exhibited potential prospects to reduce methane emissions from wetlands under reasonable management.

Microenvironment‐Responsive Hydrogels with Detachable Skin Adhesion and Mild‐Temperature Photothermal Property for Chronic Wound Healing

AbstractChronic wounds have emerged as a global healthcare burden that have inability to heal within an expected time frame owing to the complex pathophysiological microenvironment, bacterial infection, multidrug resistance, and fragile skin tissue. Tailored to the features of chronic wounds, a multifunctional hydrogel (GA) composed of ethylenediamine‐modified gelatin (Gela‐amino) and oxidized sodium alginate (Alg─CHO) is reported. The thermosensitivity of gelatin and Schiff base bonds endow GA hydrogels with physiological temperature‐enhanced nonirritating tissue adhesion and low‐temperature‐triggered nondestructive separation, beneficial for the management of vulnerable and sensitive wounds. In addition, GA hydrogels exhibit pH‐responsive degradation that adapt to the acidic wound microenvironment. Under near‐infrared (NIR) irradiation, DNase I enzyme and indocyanine green‐loaded GA hydrogels (DI@GA) efficiently eradicate drug‐resistant bacteria biofilm and subsequently exert an antibacterial effect attributed to the bioactity of GA hydrogels and mild‐temperature photothermal therapy (≈45 °C). Remarkably, DI@GA/NIR hydrogels accelerate diabetic wound recovery and skin regeneration by dispersing biofilm, killing bacteria, inhibiting inflammation, promoting collagen deposition, and improving angiogenesis. The advanced hydrogels without the addition of antibiotics are promising to act as skin‐friendly wound dressings for rescuing infectious and stalled chronic wounds.

In Vitro Biofilm-Mediated Biodegradation of Pesticides and Dye-Contaminated Effluents Using Bacterial Biofilms.

Overuse of pesticides in agricultural soil and dye-polluted effluents severely contaminates the environment and is toxic to animals and humans making their removal from the environment essential. The present study aimed to assess the biodegradation of pesticides (cypermethrin (CYP) and imidacloprid (IMI)), and dyes (malachite green (MG) and Congo red (CR)) using biofilms of bacteria isolated from pesticide-contaminated soil and dye effluents. Biofilms of indigenous bacteria, i.e., Bacillus thuringiensis 2A (OP554568), Enterobacter hormaechei 4A (OP723332), Bacillus sp. 5A (OP586601), and Bacillus cereus 6B (OP586602) individually and in mixed culture were tested against CYP and IMI. Biofilms of indigenous bacteria i.e., Lysinibacillus sphaericus AF1 (OP589134), Bacillus sp. CF3 (OP589135) and Bacillus sp. DF4 (OP589136) individually and in mixed culture were tested for their ability to degrade dyes. The biofilm of a mixed culture of B. thuringiensis + Bacillus sp. (P7) showed 46.2% degradation of CYP compared to the biofilm of a mixed culture of B. thuringiensis + E. hormaechei + Bacillus sp. + B. cereus (P11), which showed significantly high degradation (70.0%) of IMI. Regarding dye biodegradation, a mixed culture biofilm of Bacillus sp. + Bacillus sp. (D6) showed 86.76% degradation of MG, which was significantly high compared to a mixed culture biofilm of L. sphaericus + Bacillus sp. (D4) that degraded only 30.78% of CR. UV-VIS spectroscopy revealed major peaks at 224 nm, 263 nm, 581 nm and 436 nm for CYP, IMI, MG and CR, respectively, which completely disappeared after treatment with bacterial biofilms. Fourier transform infrared (FTIR) analysis showed the appearance of new peaks in degraded metabolites and disappearance of a peak in the control spectrum after biofilm treatment. Thin layer chromatography (TLC) analysis also confirmed the degradation of CYP, IMI, MG and CR into several metabolites compared to the control. The present study demonstrates the biodegradation potential of biofilm-forming bacteria isolated from pesticide-polluted soil and dye effluents against pesticides and dyes. This is the first report demonstrating biofilm-mediated bio-degradation of CYP, IMI, MG and CR utilizing soil and effluent bacterial flora from Multan and Sheikhupura, Punjab, Pakistan.

α,α-disubstituted β-amino amides eliminate Staphylococcus aureus biofilms by membrane disruption and biomass removal

Bacterial biofilms account for up to 80% of all infections and complicate successful therapies due to their intrinsic tolerance to antibiotics. Biofilms also cause serious problems in the industrial sectors, for instance due to the deterioration of metals or microbial contamination of products. Efforts are put in finding novel strategies in both avoiding and fighting biofilms. Biofilm control is achieved by killing and/or removing biofilm or preventing transition to the biofilm lifestyle. Previous research reported on the anti-biofilm potency of α,α-disubstituted β-amino amides A1, A2 and A3, which are small antimicrobial peptidomimetics with a molecular weight below 500 Da. In the current study it was investigated if these derivatives cause a fast disintegration of biofilm bacteria and removal of Staphylococcus aureus biofilms. One hour incubation of biofilms with all three derivatives resulted in reduced metabolic activity and membrane permeabilization in S. aureus (ATCC 25923) biofilms. Bactericidal properties of these derivatives were attributed to a direct effect on membranes of biofilm bacteria. The green fluorescence protein expressing Staphylococcus aureus strain AH2547 was cultivated in a CDC biofilm reactor and utilized for disinfectant efficacy testing of A3, following the single tube method (American Society for Testing and Materials designation number E2871). A3 at a concentration of 90 μM acted as fast as 100 μM chlorhexidine and was equally effective. Confocal laser scanning microscopy studies showed that chlorhexidine treatment lead to fluorescence fading indicating membrane permeabilization but did not cause biomass removal. In contrast, A3 treatment caused a simultaneous biofilm fluorescence loss and biomass removal. These dual anti-biofilm properties make α,α-disubstituted β-amino amides promising scaffolds in finding new control strategies against recalcitrant biofilms.

The effect of antibacterial photodynamic therapy with diode laser on chromogenic bacteria associated with dental black staining: An in-vitro study

BackgroundAggregatibacter actinomycetemcomitan (A.a) and Actinomyces naeslundii (A.n) are two gram-negative chromogenic bacteria involved in the formation of dental black stainings. Our study aimed to investigate the antibacterial effect of photodynamic therapy (aPDT) using two photosensitizers, Methylene Blue (MB) and Indocyanine Green (ICG). Materials and methodsIn this in-vitro study, two isolates of each selected bacterium were cultured and treated as follows; Negative control with no treatment; CHX as a positive control; ICG; MB; ICG with 808 nm laser activation; and MB with 660 nm laser activation. The number of colonies (CFU/mL) was determined to compare the groups. The qualitative evaluation of biofilm formation was done by scanning electron microscopy of treated enamel pieces. The logarithmic values of the colony counts were compared using One-way ANOVA and the Welch test Tukey HSD and Games-Howell tests were used for multiple comparisons. P-values of less than 0.05 were considered statistically significant. ResultsThe use of ICG alone or along with laser irradiation at the wavelength of 808 nm significantly reduced the number of colonies of A.a and A.n bacteria. Comparing the colony counts in the MB group with the positive control showed no significant decrease in bacterial load. On the contrary, activation of MB with 660 nm radiation of diode laser showed a significant antibacterial effect. The density of bacterial biofilm was significantly lower in the groups treated with MB and ICG without laser activation than in the control group; however, the reduction in bacteria biofilm density was more robust using photodynamic therapy with ICG. ConclusionaPDT using MB with 660 nm laser and ICG with 808 nm laser significantly reduced the number of chromogenic A.a and A.n bacteria, and photodynamic therapy with ICG was proven to be significantly more effective than MB with or without laser radiation.

Evaluation of anti-quorum sensing and antibiofilm effects of secondary metabolites from Gambeya lacourtiana (De Wild) Aubr. & Pellegr against selected pathogens

BackgroundMicrobial infections cause serious health problems especially with the rising antibiotic resistance which accounts for about 700,000 human deaths annually. Antibiotics which target bacterial death encounter microbial resistance with time, hence, there is an urgent need for the search of antimicrobial substances which target disruption of virulence factors such as biofilm and quorum sensing (QS) with selective pressure on the pathogens so as to avoid resistance.MethodsNatural products are suitable leads for antimicrobial drugs that can inhibit bacterial biofilms and QS. Twenty compounds isolated from the medicinal plant Gambeya lacourtiana were evaluated for their antibiofilm and anti-quorum sensing effects against selected pathogenic bacteria.ResultsMost of the compounds inhibited violacein production in Chromobacterium violaceum CV12472 and the most active compound, Epicatechin had 100% inhibition at MIC (Minimal Inhibitory Concentration) and was the only compound to inhibit violacein production at MIC/8 with percentage inhibition of 17.2 ± 0.9%. Since the bacteria C. violaceum produces violacein while growing, the inhibition of the production of this pigment reflects the inhibition of signal production. Equally, some compounds inhibited violacein production by C. violaceum CV026 in the midst of an externally supplied acylhomoserine lactone, indicating that they disrupted signal molecule reception. Most of the compounds exhibited biofilm inhibition on Staphyloccocus aureus, Escherichia coli and Candida albicans and it was observed that the Gram-positive bacteria biofilm was most susceptible. The triterpenoids bearing carboxylic acid group, the ceramide and epicatechin were the most active compounds compared to others.ConclusionSince some of the compounds disrupted QS mediated processes in bacteria, it indicates that this plant is a source of antibiotics drugs that can reduce microbial resistance.

A near-infrared light-triggered nano-domino system for efficient biofilm eradication: Activation of dispersing and killing functions by generating nitric oxide and peroxynitrite via cascade reactions

One of the serious threats to global public health is the bacterial biofilm, which results in numerous persistent and recurrent infections. Herein, we proposed a near-infrared (NIR) light-triggered “nano-domino” system with “dispersing and killing” functionality for biofilm eradication. The nanoplatform was fabricated by the self-assembly of chitosan conjugated with L-arginine (L-Arg, a natural nitric oxide (NO) donor) and indocyanine green (ICG, a phototherapy agent). Using an NIR irradiation “trigger”, a series of reactive oxygen species (ROS) including singlet oxygen (1O2), hydrogen peroxide (H2O2), and superoxide anions (·O2−), as well as heat were generated from ICG aggregates. Subsequently, 1O2 and H2O2 catalyzed L-Arg to produce NO, which dispersed the biofilm and reacted with ·O2− to form peroxynitrite to kill bacteria with ROS collaboratively. Meanwhile, the generated heat increased the permeability of bacterial membranes, aggravating the damage to biofilm bacteria. The experiments on biofilm eradication demonstrated that this “nano-domino” system was capable to eradicate over 99.99% of biofilms formed by Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa under 5-min NIR irradiation. Notably, these integrated benefits allowed the system to promote the healing of MRSA biofilm-infected wounds in vivo with negligible toxicity. Overall, this reported NIR-triggered “nano-domino” system holds great promise for addressing the difficulties associated with bacterial biofilm eradication. Statement of significanceNovel agents for biofilm eradication are urgently needed due to the alarming rise in antimicrobial resistance to conventional antibiotics and the critical shortage of new drugs. In this study, we created a nano-domino system that uses near-infrared (NIR) light as a trigger to eradicate mature biofilms. In response to a short-term NIR irradiation, the proposed nanoplatform could generate nitric oxide and peroxynitrite to disperse the biofilm and kill the bacteria inside, respectively, leading to efficient eradication of Methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa biofilms with minimal cytotoxicity. The findings, therefore, indicate that this nanoplatform with enhanced antibiofilm performance might provide a reliable and promising solution to biofilm-related problems.

2-arylydene indan-1,3-diones as promising candidates to inhibit bacterial biofilm formation

Biofilms are a bacterial community attached to inert or living surfaces, enveloped within a matrix of extracellular polymeric substances. This protection allows the growth and survival of bacteria in hostile environments and provides greater resistance and tolerance to antimicrobials and sanitizers. Given their propensity to form on diverse of surfaces, biofilms have significant impacts across multiple sectors, including healthcare and the industrial domains. Aiming at the development of strategies for the control and removal of bacterial biofilms, this work evaluated the impact of nineteen 2-arylidene indan-1,3-diones on both biofilm formation and preformed biofilms across various bacterial strains. The compounds exhibited a minimum inhibitory concentration (MIC) higher than 160 µg/mL, with antibiofilm assays performed at a concentration of 100 µg/mL. Among the compounds tested, the most effective in inhibiting biofilm formation were Ap18 (2-(3,4-dimethoxybenzylidene)-1H-indene-1,3(2H)-dione) against S. aureus (66.2%), Ap28 (2-(3-hydroxybenzylidene)-1H-indene-1,3(2H)-dione) against S. epidermidis (82.2%), Ap3 (2-(4-nitrobenzylidene)-1H-indene-1,3(2H)-dione) against E. coli (54.3%), and Ap25 (2-(3-hydroxy-4-methoxybenzylidene)-1H-indene-1,3(2H)-dione) against P. aeruginosa (70.8%). After 6 h, Ap18 disrupted the preformed biofilm of E. coli by 53.5% but had weak activity on the preformed biofilms of the other bacteria. The viability of VERO cells when incubated with the compounds Ap8, Ap25, and Ap27 (2-(2-hydroxybenzylidene)-1H-indene-1,3(2H)-dione) was respectively 81.8%, 67.9% and 88.0%, showing their low toxicity. This is the first work that demonstrated the antibiofilm activity of 2-arylidene indan-1,3-diones. The results can be explored to support the synthesis of more effective and less cytotoxic compounds.

Precision Dosing of Antibiotics and Potentiators by Hypoxia-Responsive Nanoparticles for Overcoming Antibiotic Resistance in Gram-Negative Bacteria.

The stalling development of antibiotics, especially against intrinsically resistant Gram-negative pathogens associated with outer membranes, leads to an emerging antibiotic crisis across the globe. To breathe life into existing drugs, we herein report a hypoxia-responsive nanoparticle (NP) that encapsulates a hydrophobic antibiotic, rifampicin, and a cationic potentiator, polysulfonium. The simultaneous release of antibiotics and potentiators can be promoted and inhibited in response to the severity of bacterial-induced hypoxia, leading to antimicrobial dosing in a precision manner. Under the synergism of polysulfoniums with membrane-disruption capability, the NPs can intensively decrease the antibiotic dose by up to 66-95% in eliminating planktonic Gram-negative P. aeruginosa bacteria and achieve an 8-log reduction of bacteria in mature biofilms at rifampicin MIC. The NP formulation demonstrates that precision dosing of antibiotics and potentiators regulated by hypoxia provides a promising strategy to maximize efficacy and minimize toxicity in treating Gram-negative bacterial infection.