Inhibit Biofilm Formation Research Articles

Development of Synthetic Antimicrobial Peptides Based on Genomic Analysis of Streptococcus salivarius.

In the oral environment, the production of bacteriocins or antimicrobial peptides (AMPs) plays a crucial role in maintaining ecological balance by impeding the proliferation of closely related microorganisms. This study aims to conduct in silico genome screening of Streptococcus salivarius to identify potential antimicrobial compounds existing as hypothetical peptides, with the goal of developing novel synthetic antimicrobial peptides. Draft genomes of various oral Streptococcus salivarius strains were obtained from the NCBI database and subjected to analysis using bioinformatic tools, viz. Expert Protein-Analysis System (Expasy), UniProt Knowledgebase (UniProtKB), European Molecular Biology Open Software Suite (EMBOSS), Pepwheel, and PEP-FOLD Peptide Structure Prediction Server. The antimicrobial potential of peptides was assessed through the Antimicrobial Peptide Database (AMP) and Bactibase. Two short peptides, viz. synthetic antimicrobial peptides (SAMPs), were designed based on current knowledge of hydrophobic and cationic residues, synthesized, and their efficacy against biofilm formation was evaluated with standard microbiological methods. The synthesized short peptides reduced the growth and effectively inhibited biofilm formation by specific oral microbial strains, demonstrating their potential as antimicrobial peptides. Furthermore, the alignment of bacteriocin biosynthetic clusters among streptococcus strains revealed variations in putative bacteriocin amino acid sequences across different strains of the same organism. Streptococcus salivarius emerges as a promising bioresource for the development of novel antimicrobial agents, particularly for combating biofilm-associated oral infections.

Synthesis and Biological Evaluation of Bile Acid-Triclosan Conjugates: A Study on Antibacterial, Antibiofilm, and Molecular Docking.

This work describes the synthesis, characterization, and antibacterial properties of four bile acid-triclosan conjugates. The in vitro antibacterial activity of synthetic bile acid-triclosan conjugates was investigated against a panel of Gram-positive and Gram-negative bacteria. Conjugates 3 and 4 show high activity against Escherichia coli (ATCC25922), with IC50 values of 2.94 ± 0.7 and 1.51 ± 0.05 μM, respectively. Conjugate 4 demonstrated 9 times the activity of triclosan (6.77 μM) and 18 times the potency of kanamycin, a well-known antibiotic. Compound 3 showed higher potential activity against all evaluated strains, including Bacillus megaterium (IC50: 3.05 ± 0.02), Bacillus amyloquefaciens (IC50: 8.79 ± 0.01), Serratia marcescens (IC50: 6.77 ± 0.4), and E. coli (IC50: 1.51 ± 0.05 μM). These findings indicate that it has broad-spectrum antibacterial activity. Bile acid-triclosan conjugates prevent biofilms by up to 99% at low doses (conjugates 4; 4.16 ± 0.8 μM), compared to triclosan. Conjugate 5 was most potent against B. amyloquefaciens (IC50 = 5.23 ± 0.2 μM), while conjugate 4 was most effective against B. megaterium (IC50 = 4.16 ± 0.8 μM) in biofilm formation. These conjugates inhibit biofilm formation by limiting the extracellular polymeric substance generation. The in vitro antibacterial study revealed that bile acid-triclosan conjugates were more effective than the parent molecule triclosan at inhibiting bacterial growth and biofilm formation against both Gram-positive and Gram-negative bacteria.

High-level biosynthesis and purification of the antimicrobial peptide Kiadin based on non-chromatographic purification and acid cleavage methods

Antimicrobial peptides (AMPs) are renowned for their potent bacteriostatic activity and safety, rendering them invaluable in animal husbandry, food safety, and medicine. Despite their potential, the physiological toxicity of AMPs to host cells significantly hampers their biosynthetic production. This study presents a novel approach for the biosynthesis of the antimicrobial peptide Kiadin by engineering a DAMP4–DPS–Kiadin fusion protein to mitigate host cell toxicity and achieve high-level expression. Leveraging the unique properties of the DAMP4 protein, we developed a non-chromatographic purification method to isolate the DAMP4–DPS–Kiadin fusion protein with high purity. The instability of the D–P peptide bond under acidic conditions, combined with the thermal and saline stability of DAMP4, enabled efficient separation of Kiadin through acid cleavage and isoelectric precipitation, yielding Kiadin with 96% purity and a production yield of 29.3 mg/L. Our optimization of acid cleavage temperature, duration, and isoelectric precipitation conditions proved critical for maximizing the purification efficiency and expression levels of Kiadin. The biosynthesized Kiadin exhibited robust bacteriostatic activity against Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Bacillus cereus and Staphylococcus aureus. Notably, Kiadin demonstrated significant post-antibiotic effects by disrupting bacterial membrane integrity, inducing cytoplasmic leakage, and inhibiting biofilm formation in E. coli K88 and S. aureus Mu50, without cytotoxicity towards mouse macrophages. In vivo studies further confirmed Kiadin's exceptional therapeutic efficacy against abdominal infections caused by E. coli K88. The acid cleavage and non-chromatographic purification techniques developed in this study offer a cost-effective and efficient strategy for the high-purity production of AMPs.

Enhanced bacteriostatic effects of phage vB_C4 and cell wall-targeting antibiotic combinations against drug-resistant Aeromonas veronii.

Aeromonas veronii is a vital zoonotic pathogen known for its extensive drug resistance and ability to form biofilms, which contribute to its antibiotic resistance. In this study, the phage vB_C4, specifically targeting A. veronii, was isolated and subjected to bioinformatic analysis and bacteriostatic activity assays. The combination of phage vB_C4 with antibiotics such as cephalothin and cefoxitin, which target the bacterial cell wall, resulted in a significantly enhanced bacteriostatic effect compared to either the phage or antibiotics alone. Furthermore, the phage dosage was critical in optimizing the antimicrobial effect when used in conjunction with antibiotics. This combined treatment exhibited a more distinct effect in removing mature biofilms and inhibiting biofilm formation, leading to a considerable decrease in bacterial density within the biofilm. Overall, the synergistic use of phage and antibiotics offers a novel attitude for treating pathogenic bacteria and holds significant potential in preventing the emergence of drug-resistant strains.IMPORTANCEThe combined application of phages and antibiotics not only effectively inhibits the emergence of phage-resistant bacteria but also reduces the required effective concentration of antibiotics. Additionally, this combination therapy demonstrates significant therapeutic effects on clinical infections mediated by biofilms. Consequently, this study establishes a basis for evaluating the parameters essential for utilizing phage-antibiotic combination therapy in the treatment of biofilm-associated infections, thereby offering a novel selection for the clinical management of multidrug-resistant bacterial infections.

Unveiling the structural aspects of novel azo-dyes with promising anti-virulence activity against MRSA: a deep dive into the spectroscopy via integrated experimental and computational approaches.

A novel series of azo dyes was successfully synthesized by combining amino benzoic acid and amino phenol on the same molecular framework via azo linkage. The structural elucidation of these dyes was carried out using various spectroscopic techniques, including UV-vis, FT-IR, NMR spectroscopy, and HRMS. Surprisingly, the aromatic proton in some dyes exhibited exchangeability in D2O, prompting a 2D NMR analysis to confirm this phenomenon. Furthermore, comprehensive density functional theory (DFT) calculations were conducted to unravel synthetic dyes' geometrical and electronic properties. Meanwhile, the reactivity of various sites was further investigated through Frontier Molecular Orbitals (FMOs) analysis and molecular electrostatic potential mapping. Besides, the experimental NMR spectra were interpreted by incorporating theoretically computed NMR spectrum and reduced density gradient (RDG) function. These computations revealed a pronounced intramolecular hydrogen bond through O-H⋯N interaction that significantly influenced the proton chemical shift. The dyes were assessed for their antimicrobial activities using agar diffusion, micro broth dilution, and biofilm inhibition assays. Interestingly, one of the synthetic dyes showed promising antibacterial effects against S. aureus (ATCC-6538) as well as against a multidrug-resistant MRSA clinical isolate with a MIC (minimum inhibitory concentration) of 78.12 μg mL-1. Moreover, that dye inhibited biofilm formation of the strong biofilm former clinical MRSA isolate with a concentration as low as 0.25 MIC (19.53 μg mL-1). Indeed, our qPCR data suggest that inhibiting the SaeS/SaeR system is another potential mechanism by which D4 exerts its antibacterial and anti-virulence effects. Altogether, this shows these synthetic azo dyes' promising antibacterial and anti-virulence activities concerning MRSA clinical infections.

Innovative antifungal strategies: enhanced biofilm inhibition of Candida albicans by a modified tea tree oil formulation

IntroductionCandida albicans is a significant human pathogen with the ability to form biofilms, a critical factor in its resistance to antifungal treatments. This study aims to evaluate the antifungal activity and biofilm inhibition potential of Tea Tree Oil (TTO) derived from Melaleuca alternifolia cultivated in Vietnam.MethodsThe antifungal activity of TTO was assessed by determining the Minimum Inhibitory Concentration (MIC), Minimum Fungicidal Concentration (MFC), Minimum Biofilm Inhibitory Concentration (MBIC), and Minimum Biofilm Eradication Concentration (MBEC) using broth dilution methods. The experiments were conducted on C. albicans in both planktonic and biofilm states across concentrations ranging from 0.1 μL/mL to 10 μL/mL.ResultsTTO demonstrated significant antifungal efficacy, with a MIC of 0.1 μL/mL (∼91.217 μg/mL) and an MFC of 10 μL/mL (∼9121.7 μg/mL). It effectively inhibited biofilm formation with a recorded MBIC of 2 μL/mL (∼1824.34 μg/mL). However, MBEC values were not determinable as the concentrations tested did not achieve the eradication of more than 50% of mature biofilm within the experimental conditions.DiscussionThese findings highlight TTO as a promising natural antifungal agent with strong biofilm-inhibitory properties. However, its limited efficacy in eradicating mature biofilms underscores the need for further studies, potentially involving higher concentrations or synergistic combinations with conventional antifungal agents.

Characterization and enhanced antibiofilm activity of Annona muricata extract in combination with fluconazole against Candida albicans.

Candida albicans biofilm formation is a significant contributor to antifungal resistance, necessitating new treatment strategies. Annona muricata Lin., a traditional herbal remedy, has shown promise in combating microbial infections. The purpose of this study was to assess the antibiofilm activity of the methanol extract of A. muricata leaves alone or with the addition of fluconazole against C. albicans. Phytochemicals from the methanol extract were analyzed by LC-MS, the XTT assay was used for metabolic activity, and morphological characteristics were examined using scanning electron microscopy (SEM). Molecular docking screening of identified compounds in A. muricata methanol leaves extract against a Sap3 receptor (PDB: 2H6T) was also performed. The LC-MS analysis detected 17 possible phytochemicals. The methanol extract showed a dose-dependent inhibition of biofilm formation, with maximum inhibition of ~60% observed at 240 μg/ml, and inhibition by fluconazole increased from 32% to 76% as the concentration increased from 15 to 240 μg/ml. The combination of A. muricata and fluconazole increased the inhibition significantly, from 74% to 78% at 15 μg/ml to 240 μg/mL, respectively. SEM of control and treated C. albicans biofilms showed an altered morphology and loss of cell integrity by the combination, corroborating the findings. Plant phytochemicals also possess high binding affinity (-9.7 to 8.0 kcal/mol, respectively) for the Sap3 enzyme and may therefore have therapeutic potential against C. albicans. Consequently, the findings indicate that compounds in the A. muricata methanol extract may function in concert with fluconazole at sub-inhibitory concentrations to suppress C. albicans biofilm formation. This finding paves the way for the formulation and development of antifungal treatment regimens that may limit the development of fluconazole resistance employing this plant part.

Characterization and genomic insights into bacteriophages Kpph1 and Kpph9 against hypervirulent carbapenem-resistant Klebsiella pneumoniae

ABSTRACT The increasing incidence of infections attributed to hypervirulent carbapenem-resistant Klebsiella pneumoniae (Hv-CRKp) is of considerable concern. Bacteriophages, also known as phages, are viruses that specifically infect bacteria; thus, phage-based therapies offer promising alternatives to antibiotic treatments targeting Hv-CRKp infections. In this study, two isolated bacteriophages, Kpph1 and Kpph9, were characterized for their specificity against the Hv-CRKp K. pneumoniae NUHL30457 strain that possesses a K2 capsule serotype. Both phages exhibit remarkable environmental tolerance, displaying stability over a range of pH values (4–11) and temperatures (up to 50°C). The phages demonstrate potent antibacterial and antibiofilm efficacy, as indicated by their capacity to inhibit biofilm formation and to disrupt established biofilms of Hv-CRKp. Through phylogenetic analysis, it has been revealed that Kpph1 belongs to the new species of Webervirus genus, and Kpph9 to the Drulisvirus genus. Comparative genomic analysis suggests that the tail fiber protein region exhibits the greatest diversity in the genomes of phages within the same genus, which implies distinct co-evolution histories between phages and their corresponding hosts. Interestingly, both phages have been found to contain two tail fiber proteins that may exhibit potential depolymerase activities. However, the exact role of depolymerase in the interaction between phages and their hosts warrants further investigation. In summary, our findings emphasize the therapeutic promise of phages Kpph1 and Kpph9, as well as their encoded proteins, in the context of research on phage therapy targeting hypervirulent carbapenem-resistant Klebsiella pneumoniae.

Potential Use of Selected Natural Compounds with Anti-Biofilm Activity.

Antibiotic resistance in microorganisms is an escalating global concern, exacerbated by their formation of biofilms, which provide protection through an extracellular matrix and communication via quorum sensing, enhancing their resistance to treatment. This situation has driven the search for alternative approaches, particularly those using natural compounds. This study explores the potential of phytochemicals, such as quercetin, apigenin, arbutin, gallic acid, proanthocyanidins, and rutin, known for their antibacterial properties and ability to inhibit biofilm formation and disrupt mature biofilms. The methods used in this study included a comprehensive review of current literature assessing the bioavailability, distribution, and effective concentrations of these compounds in treating biofilm-associated infections. The results indicate that these phytochemicals exhibit significant antibacterial effects, reduce biofilm's structural integrity, and inhibit bacterial communication pathways. Moreover, their potential use in combination with existing antibiotics may enhance therapeutic outcomes. The findings support the conclusion that phytochemicals offer promising additions to anti-biofilm strategies and are capable of complementing or replacing conventional treatments, with appropriate therapeutic levels and delivery mechanisms being key to their effectiveness. This insight underscores the need for further research into their clinical applications for treating infections complicated by biofilms.

Antimicrobial Efficacy of Trifluoro-Anilines Against Vibrio Species.

Vibrios are naturally present in marine ecosystems and are commonly allied with live seafood. Vibrio species frequently cause foodborne infections, with Vibrio parahaemolyticus recently becoming a significant contributor to foodborne illness outbreaks. In response, aniline and 68 of its aniline derivatives were studied due to their antibacterial effects targeting V. parahaemolyticus and Vibrio harveyi. Among these, 4-amino-3-chloro-5-nitrobenzotrifluoride (ACNBF) and 2-iodo-4-trifluoromethylaniline (ITFMA) demonstrated both antibacterial and antibiofilm properties. The minimum inhibitory concentrations (MIC) for ACNBF and ITFMA were 100 µg/mL and 50 µg/mL, respectively, against planktonic cells. The active compounds effectively suppressed biofilm formation in a manner dependent on the dosage. Additionally, these trifluoro-anilines significantly reduced virulence factors such as motility, protease activity, hemolysis, and indole production. Both trifluoro-anilines caused noticeable destruction to the membrane of bacterial cells and, at 100 µg/mL, exhibited bactericidal activity against V. parahaemolyticus within 30 min. Toxicity assays using the Caenorhabditis elegans and seed germination models showed that the compounds displayed mild toxicity. As a result, ACNBF and ITFMA inhibited the growth of both planktonic cells and biofilm formation. Furthermore, these active compounds effectively prevented the formation of biofilm on the surfaces of shrimp and squid models, highlighting their potential use in controlling seafood contamination.

CISTUS CRETICUS L.: ANTIOBESITY, ANTIMICROBIAL AND ANTIBIOFILM PROPERTIES

Objective: Cistus creticus L. is widespread in the coastal regions of Türkiye. In this study, we investigated the cytotoxic, antiobesity, antimicrobial and antibiofilm properties as well as the total phenolic and flavonoid content of both aqueous and ethanolic extracts in vitro. Material and Method: Two different extracts were prepared from the flowering aerial parts of Cistus creticus using ethanol and water. The total phenolic content and total flavonoids were determined by the Folin-Ciocalteu method and the aluminum chloride colorimetry, respectively. The effect of extracts on the cell viability of 3T3-L1 was determined by methyl thiazole tetrazolium (MTT), and the evaluation of differentiation and the effects of the plant extracts on lipid accumulation in 3T3-L1 adipocytes was performed by Oil-Red O staining. In addition, MIC values and antibiofilm activities were also investigated. Result and Discussion: The total phenol content of the EtOH and water extract was determined to be 134.2849 mg GAE/g and 96.1803 mg GAE/g, respectively. The total flavonoids in the water and EtOH extracts were found to be 33.1942 mgQE/g and 22.8338 mgQE/g, respectively. The lowest MIC values were determined for the strains Bacillus subtilis DSM 1971, Bacillus licheniformis DSM 13 and Bacillus amyloliquefaciens DSM 7, while the highest MIC concentration was found for the strains Escherichia coli and Eenterococcus gallinarum. The MIC/16 concentration of Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922 also proved to be effective in inhibiting biofilm formation. We observed that noticeable but not strong effects on lipid accumulation were observed in 3T3-L1 adipocytes treated with EtOH extract.

The Effect of Surface Functionalization of Magnesium Alloy on Degradability, Bioactivity, Cytotoxicity, and Antibiofilm Activity.

Magnesium alloys are promising biomaterials to be used as temporary implants due to their biocompatibility and biodegradability. The main limitation in the use of these alloys is their rapid biodegradation. Moreover, the risk of microbial infections, often following the implant surgery and hard to eradicate, is another challenge. Thus, with the aim of reducing biodegradability and conferring antibiofilm activity, sheets of the magnesium alloy AZ31 were properly modified with the introduction of hydroxy (polyethyleneoxy)propyl silane (PEG) and quaternary ammonium silane chains (QAS). The derivatized sheets were characterized by ATR-FTIR spectroscopy and their performances as concerns their stability, Mg2+ in vitro release, and in vitro bioactivity were evaluated as well. The results showed an increased stability with a reduction in corrosion, a slower Mg2+ ion release, and the formation of hydroxyapatite in the sheets' surface. In addition, cytotoxicity evaluations were carried out on human gingival fibroblasts showing that the AZ31 and AZ31-PEG plates had good cytocompatibility. Finally, the antibiofilm activity on Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa was carried out by evaluating the capacity of inhibition of biofilm adhesion and formation. The results demonstrated a significant reduction in biofilm formation by Staphylococcus epidermidis on AZ31-QAS.

Cinnamic Acid Compounds (p-Coumaric, Ferulic, and p-Methoxycinnamic Acid) as Effective Antibacterial Agents Against Colistin-Resistant Acinetobacter baumannii.

Colistin-resistant Acinetobacter baumannii (COLR-Ab) is an opportunistic pathogen commonly associated with nosocomial infections, and it is difficult to treat with current antibiotics. Therefore, new antimicrobial agents need to be developed for treatment. Based on this information, we investigated the antimicrobial, antibiofilm, and combination activities of p-coumaric acid (p-CA), ferulic acid (FA), and p-methoxycinnamic acid (p-MCA) against five COLR-Ab isolates. p-CA, FA, and p-MCA exhibited antimicrobial activity against COLR-Ab isolates, with minimum inhibitory concentration (MIC) values in the range of 256-128 µg/mL, 1024-512 µg/mL, and 512-128 µg/mL, respectively. The combination effects of the compounds with colistin (COL) were evaluated using a checkerboard synergy test. The combinations exhibited a synergistic effect and caused a 128- to 16-fold decrease in COL MIC values. In addition, the biofilm production capacities of the COLR-Ab isolates and the antibiofilm activities of the compounds were determined using the microtitre plate-based crystal violet (CV) technique. The compounds showed effective antibiofilm activity against strong and moderate biofilm-producing isolates, inhibiting biofilm formation by 77.5% and 19.7%. Spectrometric measurements were used to examine the effect of compounds on membrane permeability; 1.9-, 1.66-, and 1.34-fold increases in absorbance values were observed at MIC concentrations of p-CA, FA, and p-MCA, respectively. Furthermore, morphological changes caused by the compounds in the isolate were observed using scanning electron microscopy (SEM) micrographs. According to the WST assay, the compounds did not show any statistically significant cytotoxic effect on the cells (p > 0.05). These findings indicate that p-CA, FA, and p-MCA may be potential new alternative candidates against resistant A. baumannii.

Novel Leech Antimicrobial Peptides, Hirunipins: Real-Time 3D Monitoring of Antimicrobial and Antibiofilm Mechanisms Using Optical Diffraction Tomography.

Antimicrobial peptides (AMPs) are promising agents for treating antibiotic-resistant bacterial infections. Although discovering novel AMPs is crucial for combating multidrug-resistant bacteria and biofilm-related infections, their clinical potential relies on precise, real-time evaluation of efficacy, toxicity, and mechanisms. Optical diffraction tomography (ODT), a label-free imaging technology, enables real-time visualization of bacterial morphological changes, membrane damage, and biofilm formation over time. Here, a computational analysis of the leech transcriptome using an advanced AI-based peptide screening strategy with ODT to identify potential AMPs is employed. Among the 19 potential AMPs identified, hirunipin 2 demonstrates potent antibacterial activity, low mammalian cytotoxicity, and minimal hemolytic effects. It demonstrates efficacy comparable to melittin, resistance to physiological salts and human serum, and a low likelihood of inducing bacterial resistance. Microscopy and 3D-ODT confirm its disruption of bacterial membranes and intracellular aggregation, leading to cell death. Notably, hirunipin 2 effectively inhibits biofilm formation, eradicates preformed biofilms, and synergizes with antibiotics against multidrug-resistant Acinetobacter baumannii (MDRAB) by enhancing membrane permeability. Additionally, hirunipin 2 significantly suppresses pro-inflammatory cytokine expression in LPS-stimulated macrophages, highlighting its anti-inflammatory properties. These findings highlight hirunipin 2 as a strong candidate for developing novel antibacterial, anti-inflammatory, and antibiofilm therapies, particularly against multidrug-resistant bacterial infections.

Green Tea Extract (Theaceae; Camellia sinensis L.): A Promising Antimicrobial, Anti-Quorum Sensing and Antibiofilm Candidate Against Multidrug-Resistant Campylobacter Species.

Thermophilic Campylobacter species are among the main culprits behind bacterial gastroenteritis globally and have grown progressively resistant to clinically important antimicrobials. Many studies have been carried out to explore innovative and alternative strategies to control antibiotic-resistant campylobacters in animal reservoirs and human hosts; however, limited studies have been performed to develop efficient control schemes against Campylobacter biofilms. This study investigated the antimicrobial and antibiofilm activities of some herbal extracts against multidrug-resistant (MDR) Campylobacter species recovered from different sources using phenotypic and molecular techniques. The overall Campylobacter species prevalence was 21.5%, representing 15.25% and 6.25% for C. jejuni and C. coli, respectively. Regarding C. jejuni, the highest resistance rate was observed for amoxicillin-clavulanic acid and colistin (85.25% each), followed by cefotaxime (83.61%) and tetracycline (81.97%), whereas C. coli isolates showed absolute resistance to cefotaxime followed by erythromycin (92%) and colistin (88%). Remarkably, all Campylobacter isolates were MDR with elevated multiple antimicrobial resistance (MAR) indices (0.54-1). The antimicrobial potentials of green tea (Camellia sinensis), rosemary (Rosmarinus officinalis) and ginger (Zingiber officinale) extracts against MDR Campylobacter isolates were assessed by the disk diffusion assay and broth microdilution technique. Green tea extract showed a marked inhibitory effect against tested isolates, exhibiting growth inhibition zone diameters of 8 to 38 mm and a minimum inhibitory concentration (MIC) range of 1.56-3.12 mg/mL, unlike the rosemary and ginger extracts. Our findings reveal a respectable antibiofilm activity (>50% biofilm formation inhibition) of green tea against the preformed biofilms of Campylobacter isolates. Furthermore, real-time quantitative polymerase chain reaction (RT-qPCR) results showed a significant decrease (p < 0.05) in the expression levels of biofilm biosynthesis gene and its regulator (FlaA and LuxS, respectively) in Campylobacter isolates treated with the green tea extract in comparison with untreated ones. This is the first in vitro approach that has documented the inhibitory activity of green tea extract against MDR-biofilm-producing Campylobacter species isolated from different sources. Further in vivo studies in animals' models should be performed to provide evidence of concept for the implementation of this alternative candidate for the mitigation of MDR Campylobacter infections in the future.

Galangin synergistically revives the antibacterial activity of vancomycin against vancomycin-resistant Enterococcus faecium.

Enterococcus faecium is one of the most important opportunistic pathogens threatening human health worldwide. Resistance to vancomycin (VAN) is increasing at an alarming rate. Resurrecting antibiotics using a combination approach is a promising alternative avenue. Galangin (GAL) is a bioactive compound constituted in herbal plants. This study aimed to evaluate the synergistic activity of the combination of GAL and VAN and mode of action against vancomycin-resistant E. faecium (VREfm) strains. The minimal inhibitory concentrations against these bacteria were 8-64 μg ml-1 for VAN and 512 μg ml-1 for GAL. The VAN plus GAL combination exhibited synergistic effects against E. faecium isolates, with a fraction inhibitory concentration index of 0.26-0.28. Time-kill assays confirmed this synergism. Mechanistic studies showed that the combination induced intracellular constituent leakage, suggesting impaired membrane permeability and electron microscopy revealed peptidoglycan and membrane damage. Additionally, the GAL plus VAN combination inhibited biofilm formation and significantly reduced lipid, protein, and carbohydrate contents, as shown by Fourier-transform infrared spectroscopy (FTIR). GAL could reverse the activity of VAN against VREfm by damaging bacterial cell envelope, inhibiting biofilm formation, and reducing biomolecule contents, emphasizing its potential as a valuable adjunct to VAN in treating VREfm infections.

Study of an arginine- and tryptophan-rich antimicrobial peptide in peri-implantitis.

The combination of hydrophilic arginine residues and hydrophobic tryptophan residues is considered to be the first choice for designing short-chain antimicrobial peptides (AMPs) due to their potent antibacterial activity. Based on this, we designed an arginine- and tryptophan-rich short peptide, VR-12. Peri-implantitis is a significant microbial inflammatory disorder characterized by the inflammation of the soft tissues surrounding an implant, which ultimately leads to the progressive resorption of the alveolar bone. This study found through antibacterial experiments, wound healing promotion experiments, and anti-inflammatory experiments that VR-12 inhibited and killed planktonic peri-implantitis-associated bacteria, inhibited biofilm formation, and disrupted mature biofilms. Additionally, VR-12 exhibited good biocompatibility with RAW264.7 cells and human gingival fibroblasts (HGFs) cells, promoting proliferation of both cell types. Moreover, VR-12 induced HGFs migration by promoting expression of migration-related factors, thereby promoting soft tissue healing. VR-12 also acted on lipopolysaccharide (LPS)-induced RAW264.7 cells, exerting excellent anti-inflammatory properties by affecting the secretion/expression of inflammation-related factors/genes. Therefore, VR-12 may be a good option for both warding off and treatmenting peri-implantitis.

Unlocking the Antibacterial Potential of Naphthalimide-Coumarins to Overcome Drug Resistance with Antibiofilm and Membrane Disruption Ability against Escherichia coli.

Resistance by bacteria to available antibiotics is a threat to human health, which demands the development of new antibacterial agents. Considering the prevailing conditions, we have developed a library of new naphthalimide-coumarin moieties as broad-spectrum antibacterial agents to fight against awful drug resistance. Preliminary studies indicate that compounds 8e and 8h display excellent antibacterial activity against Escherichia coli, exceeding the performance of marketed drug amoxicillin. These drug candidates effectively inhibit biofilm formation and disrupt the biofilm virulence factor, which is accountable for the formation of strong biofilm. In addition to this, both compounds exhibit fast bactericidal properties, thus shortening the time of treatment and resisting the emergence of drug resistance for up to 20 passages. Further, biofunctional evaluation reveals that both compounds effectively disrupt the membrane, causing the leakage of cytoplasmic contents and loss in metabolic activity. Both compounds 8e and 8h efficiently induce the ROS, leading to the oxidation of GSH to GSSG, decreasing the GSH activity of the cell, and causing oxidative damage to the cells. Additionally, both compounds effectively bind with DNA to block DNA replication and form supramolecular complexes, thus exhibiting antibacterial activity. Moreover, these compounds readily bind human serum albumin with high binding constants and can be transported to the target site easily. These findings reveal that newly synthesized naphthalimide-coumarin conjugates have the potential to build as potent antibacterial agents and can be used further for clinical trials.

In vitro photodynamic therapy of Candida albicans, the cause of vulvovaginal candidiasis, is enhanced by Bacillus and Enterococcus probiotics.

Candida albicans is the primary cause of vulvovaginal candidiasis, a worldwide health concern for women. The use of supplemental methods, such as antimicrobial photodynamic therapy (aPDT) and probiotics, was promoted by the ineffectiveness of the existing antifungal drugs. This study examines the combined effects of probiotics (Bacillus and Enterococcus isolated from the fermented pickles) and PDT (using red laser (655 nm, 18 J/cm2) as a light source and methylene blue dye (30 mg/mL) as a photosensitizer) on the in vitro virulence activity of C. albicans including growth, biofilm formation, antifungal resistance, biofilm elimination, and biofilm dispersion. The probiotic strains demonstrated a higher resistance to PDT compared to the fungal cell. Bacillus and Enterococcus enhanced the antifungal effects of PDT on planktonic Candida cells in both pre-PDT and post-PDT interactions. The inhibition of biofilm formation by PDT was improved upon interaction with Bacillus (70%) and Enterococcus (58%). The eradication of Candida biofilm using PDT was increased after a combination with Bacillus (67%) and Enterococcus (46%). The nystatin resistance of the fungal biofilm following PDT treatment was decreased from (µg/ml) 25 to 6.25 due to the interaction with both probiotic strains. Fungal cell dispersion from the biofilm after PDT treatment diminished by 18% and 25% in the presence of Bacillus and Enterococcus strains. Galleria mellonella mortality was significantly changed following the PDT of the fungi/probiotic-injected larvae. This synergistic activity suggests the use of probiotics/PDT as a supplemental treatment for vulvovaginal candidiasis.

Facile and green synthesis of Ag/Cu bimetallic nanoparticles using waste banana peel extract for effective corrosion inhibition of mixed sulfate-reducing bacteria.

Microbiologically induced corrosion (MIC) is widespread in the oilfield industry, and new environmentally friendly materials are urgently needed to inhibit MIC with the increasing environmental requirements and microbial resistance problems. The synthesis method and cost of the materials are important factors that must be considered in the production and application. In this study, Ag/Cu bimetallic nanoparticles (BNPs) were synthesized by eco-friendly and sustainable method using waste banana peel extract (BPE) as a green reducing. The antibacterial and corrosion inhibition properties of Ag/Cu BNPs were investigated by using the enriched mixed strains containing sulfate-reducing bacteria (SRB) as model bacteria. The results of electron microscopy showed that the prepared BNPs exhibited spherical structure with about 19.0nm in size. The synthesized nanoparticles significantly inhibited the growth of mixed strains by antimicrobial experiments with minimum inhibitory concentration (MIC) value of 9.38μg/mL. The addition of Ag/Cu BNPs (9.38μg/mL) inhibited the corrosion of X65 carbon steel induced by the mixed strains with 77.9% compared to the untreated condition. Correspondingly, the number of sessile SRB cells in the solution containing Ag/Cu BNPs (9.38μg/mL) after 28 days of immersion decreased by 5-log compared with the treatment group without nanomaterials (1.1×108cells/cm2). Furthermore, the observation of the surface morphology and strains cellular microstructure of carbon steel treated with nanoparticle materials illustrated that the corrosion inhibition mechanism mainly includes destroying cell structure, affecting metabolic activities and inhibiting biofilm formation. The environmentally friendly nanoparticle materials prepared in this study have great potential in the safe and clean production of oil fields.