Biofilm Matrix Research Articles

Silver nanoparticles/carbon dots nanocomposite with potent antibiofilm and long-term antimicrobial activity doped into chitosan/polyvinyl alcohol film for food preservation.

Exploration of robust antiseptics with antibiofilm performance and long-term antimicrobial activity is of great significance to effectively destroy foodborne pathogenic bacteria. Herein, a silver nanoparticles (Ag NPs) /carbon dots (CDs) nanocomposite (Ag@CDs) was constructed by the reaction of Ag+ with CDs, which has strong antibacterial ability, and mighty biofilm inhibition and destruction ability toward E. coli and S. aureus. Notably, low concentration of Ag@CDs (40.0 and 80.0μg/mL) could ablate 86.11% E. coli and 75.86%S. aureus biomass of mature biofilm. To our knowledge, this is the first bactericide with powerful biofilm destruction activity. In addition, Ag@CDs exhibited long-term (30 d) antibacterial effect on the substrates of plastic, cotton, gauze, and glass. Ag@CDs was evenly dispersed into the matrix of chitosan (CS)/polyvinyl alcohol (PVA) to fabricate well-blended food packaging films. Among which, the 3% Ag-CP film exhibited improved mechanical performance, excellent UV-Vis light blocking ability, and intensive antimicrobial activity. Despite seven days of storage, 3% Ag-CP still could preserve the freshness and safety of the pork and shrimp, certifying it extends the storage life of packaged foods.

Cooperation between Coagulase and von Willebrand factor binding protein in Staphylococcus aureus fibrin pseudocapsule formation

The major human pathogen Staphylococcus aureus forms biofilms comprising of a fibrin network that increases attachment to surfaces and shields bacteria from the immune system. It secretes two coagulases, Coagulase (Coa) and von Willebrand factor binding protein (vWbp), which hijack the host coagulation cascade and trigger the formation of this fibrin clot. However, it is unclear how Coa and vWbp contribute differently to the localisation and dynamics of clot assembly in growing biofilms.Here, we address this question using high-precision time-resolved confocal microscopy of fluorescent fibrin to establish the spatiotemporal dynamics of fibrin clot formation in functional biofilms. We also use fluorescent fusion proteins to visualise the locations of Coa and vWbp in biofilms using both confocal laser scanning and high resolution highly inclined and laminated optical sheet microscopy. We visualise and quantify the spatiotemporal dynamics of fibrin production during initiation of biofilms in plasma amended with fluorescently labelled fibrinogen.We find that human serum stimulates coagulase production, and that Coa and vWbp loosely associate to the bacterial cell surface. Coa localises to cell surfaces to produce a surface-attached fibrin pseudocapsule but can diffuse from cells to produce matrix-associated fibrin. vWbp produces matrix-associated fibrin in the absence of Coa, and furthermore accelerates pseudocapsule production when Coa is present. Finally, we observe that fibrin production varies across the biofilm. A sub-population of non-dividing cells does not produce any pseudocapsule but remains within the protective extended fibrin network, which could be important for the persistence of S. aureus biofilm infections as antibiotics are more effective against actively growing cells.Our findings indicate a more cooperative role between Coa and vWbp in building fibrin networks than previously thought, and a bet-hedging cell strategy where some cells produce biofilm matrix while others do not, but instead assume a dormant phenotype that could be associated with antibiotic tolerance.

Nanoparticles in the battle against Candida auris biofilms: current advances and future prospects.

Candida auris has emerged as a significant global health threat due to its multidrug resistance and ability to form robust biofilms, particularly on medical devices and hospital surfaces. Biofilms protect C. auris from antifungal treatments and the host immune response, making infections persistent and difficult to control. This review explores the potential of nanoparticles to overcome the limitations of traditional antifungal therapies in combating C. auris biofilms. Nanoparticles, with their unique physicochemical properties, offer promising strategies to penetrate biofilm matrices, deliver antifungal agents, and disrupt biofilm structure. Various types of nanoparticles, including metallic, polymeric, lipid-based, and cyclodextrin-based, demonstrate enhanced biofilm penetration and antifungal activity. Their ability to generate reactive oxygen species, disrupt cell adhesion, and release antifungals in a controlled manner makes them ideal candidates for biofilm-targeted therapies. This review presents the current advancements in nanoparticle-based solutions, emphasizing the need for further research into their mechanisms of action, safety, and clinical application. By addressing the challenge of C. auris biofilms specifically, this review provides a critical synthesis of existing knowledge and identifies future directions for developing effective antifungal therapies using nanotechnology.

Repurposing TAK-285 as An Antibacterial Agent against Multidrug-Resistant Staphylococcus aureus by Targeting Cell Membrane.

Infections and antimicrobial resistance are becoming serious global public health crises. Multidrug-resistant Staphylococcus aureus (S. aureus) infections necessitate novel antimicrobial development. In this study, we demonstrated TAK-285, a novel dual HER2/EGFR inhibitor, exerted antibacterial activity against 17 clinical methicillin-resistant S. aureus (MRSA) and 15 methicillin sensitive S. aureus (MSSA) isolates in vitro, with a minimum inhibitory concentration (MIC) of 13.7μg/mL. At 1 × MIC, TAK-285 completely inhibited the growth of S. aureus bacterial planktonic cells, and at 2 × MIC, it exhibited a superior inhibitory effect on intracellular S. aureus SA113-GFP compared to linezolid. Moreover, TAK-285 effectively inhibited biofilm formation at sub-MIC, eradicated mature biofilm and eliminated bacteria within biofilms, as confirmed by CLSM. Furthermore, the disruption of cell membrane permeability and potential was found by TAK-285 on S. aureus, suggesting its targeting of cell membrane integrity. Global proteomic analysis demonstrated that TAK-285 disturbed the metabolic processes of S. aureus, interfered with biofilm-related gene expression, and disrupted membrane-associated proteins. Conclusively, we repurposed TAK-285 as an antimicrobial with anti-biofilm properties against S. aureus by targeting cell membrane. This study provided strong evidence for the potential of TAK-285 as a promising antimicrobial agent against S. aureus.

Quinic acid enhances kanamycin efficacy against methicillin-resistant Staphylococcus aureus biofilms.

Methicillin-resistant Staphylococcus aureus (MRSA) form biofilms that contribute to increased antimicrobial resistance, leading to treatment failure and/or relapse. It is, therefore, necessary to develop new antibiofilm strategies to eradicate MRSA biofilms. This study was aimed to evaluate the effect of the combination of quinic acid and kanamycin against the preformed biofilms of methicillin-resistant Staphylococcus aureus. Broth microdilution method was deployed to evaluate antibacterial activity. Antibiofilm activity was evaluated by crystal violet staining, 3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium-bromide (MTT) assay, and scanning electron microscopy (SEM). The checkerboard method was adopted to assess the combination effects. Quantification of exopolysaccharides was determined by the phenol-sulfuric acid method. The eDNA was quantified by spectrophotometry. Cytotoxic activity was evaluated by the MTT assay on the human embryonic kidney (HEK 293) cell line. Quinic acid, combined with kanamycin, effectively eradicated the methicillin-resistant S. aureus biofilms by affecting biofilm biomass and cell viability. Scanning electron microscopy demonstrated a less adherence of S. aureus cells was observed after treatment with quinic acid combined with kanamycin, as compared to each drug alone. The combination of quinic acid and kanamycin thus demonstrated the ability to destroy the exopolysaccharides and eDNA of biofilm matrix without any toxic effect on HEK 293 cells. Our results clearly demonstrate the possibility of using quinic acid in combination therapy, with an antibiotic, for combating infections caused by MRSA strains.

Staphylococcus epidermidis alters macrophage polarization and phagocytic uptake by extracellular DNA release in vitro

Biofilm formation shields Staphylococcus epidermidis from host defense mechanisms, contributing to chronic implant infections. Using wild-type S. epidermidis 1457, a PIA-negative mutant (1457-M10), and an eDNA-negative mutant (1457ΔatlE), this study examined the influence of biofilm matrix components on human monocyte-derived macrophage (hMDM) interactions. The wild-type strain was resistant to phagocytosis and induced an anti-inflammatory response in hMDMs, while both mutants were more susceptible to phagocytosis and triggered a pro-inflammatory response. Removing eDNA from the 1457 biofilm matrix increased hMDM uptake and a pro-inflammatory reaction, whereas adding eDNA to the 1457ΔatlE mutant reduced phagocytosis and promoted an anti-inflammatory response. Inhibiting TLR9 enhanced bacterial uptake and induced a pro-inflammatory response in hMDMs exposed to wild-type S. epidermidis. This study highlights the critical role of eDNA in immune evasion and the central role of TLR9 in modulating macrophage responses, advancing the understanding of implant infections.

Roles of Response Regulators in the Two-Component System in the Formation of Stress Tolerance, Motility and Biofilm in Salmonella Enteritidis.

Two-component systems (TCS) of Salmonella enterica serovar Enteritidis are composed of a histidine kinase and a response regulator (RR) and represent a critical mechanism by which bacteria develop resistance to environmental stress. Here, we characterized the functions of RRs in TCS in the formation of stress tolerance, motility and biofilm using twenty-six S. Enteritidis RR-encoding gene deletion mutants. The viability results unraveled their essential roles in resistance to elevated temperature (GlrR), pH alterations (GlrR, TctD, YedW, ArcA and YehT), high salt (PhoB, BaeR, CpxR, PhoP, UvrY and TctD), oxidative stress (PhoB, YedW, BaeR, ArcA, PhoP, UvrY, PgtA and QseB) and motility (ArcA, GlnG, PgtA, PhoB, UhpA, OmpR, UvrY and QseB) of S. Enteritidis. The results of the crystal violet staining, microscopy observation and Congo red binding assays demonstrated that the absence of ArcA, GlnG, PhoP, OmpR, ZraR or SsrB in S. Enteritidis led to a reduction in biofilms and an impairment in red/dry/rough macrocolony formation, whereas the absence of UvrY exhibited an increase in biofilms and formed a brown/smooth/sticky macrocolony. The results indicated the regulatory effects of these RRs on the production of biofilm matrix, curli fimbriae and cellulose. Our findings yielded insights into the role of TCSs, making them a promising target for combating S. Enteritidis.

Repurposing Benzbromarone as an Antibacterial Agent against Gram-Positive Bacteria.

The rise of antibiotic-resistant Gram-positive pathogens, particularly methicillin-resistant Staphylococcus aureus (MRSA), presents a significant challenge in clinical settings. There is a critical need for new antibacterial agents to combat these resistant strains. Our study reveals that the uricosuric drug Benzbromarone (Benz) exhibits potent antibacterial activity against Gram-positive pathogens, with minimum inhibitory concentrations (MICs) ranging from 8 to 32 μg/mL and minimum bactericidal concentrations (MBCs) ranging from 32 to 128 μg/mL against clinical isolates of S. aureus, S. epidermidis, Enterococcus faecalis, and Streptococcus agalactiae. Furthermore, Benz significantly inhibits biofilm formation at subinhibitory concentrations and eradicates mature biofilms at higher concentrations. Benz also suppresses the hemolytic activity of S. aureus, indicating its potential to reduce virulence. Proteomic and in vitro induced resistance analyses indicate that Benz inhibits protein synthesis and turnover. Additionally, Benz induces membrane depolarization and increases membrane permeability, likely by targeting the membrane phospholipid phosphatidylethanolamine (PE). In the mouse wound infection model, Benz promotes wound healing and significantly reduces bacterial load. These findings suggest that Benz is a promising candidate for developing new antibacterial therapies against Gram-positive bacterial infections.

Optimizing Red Light-Based Photodynamic Therapy for Effective Bactericidal Action Against Fusobacterium nucleatum Subspecies.

Fusobacterium nucleatum (F. nucleatum), a key pathogen implicated in periodontal disease, contributes to oral biofilm maturation and is linked to development of systemic diseases like colorectal cancer and liver cirrhosis. Photodynamic therapy (PDT) combined with 5-aminolevulinic acid (5-ALA) treatment (ALA-PDT) selectively targets F. nucleatum by inducing porphyrin accumulation. The bactericidal effect of red light-based PDT on F. nucleatum has not been evaluated previously. This study investigates the effect of ALA-PDT using red light-emitting diode (LED) light on F. nucleatum subspecies and their porphyrin accumulation. F. nucleatum subspecies were cultured with varying concentrations of 5-ALA under anaerobic conditions. Porphyrin accumulation was measured via fluorescence spectroscopy, and colony-forming units were measured to determine bacterial viability post-treatment. Additionally, other subspecies responded well to 0.01% 5-ALA, and uroporphyrin I accumulation correlated with bacterial death, revealing optimal bactericidal conditions. These results suggest that optimizing light intensity and 5-ALA concentration can significantly enhance the therapeutic potential of ALA-PDT in oral healthcare.

Estimation of Biofilm Components and Prevalence of SDR Genes among Staphylococcus Aureus Isolated from Anbar Hospitals

Background Nosocomial infections, a major health problem, are due at 80% to biofilm‐associated infection. Staphylococcus aureus, a prominent biofilm producer, has both MRSA and MSSA biofilm-forming capabilities that highlight its persistence in hospital environments. In previous studies, less focus was given to the components of the biofilms. Therefore, understanding biofilm composition has become crucial. Objective In this study, the components in the biofilm matrix in MRSA and MSSA isolates were estimated, and the prevalence of sdr genes (sdrC,sdrD,sdrE) among S. aureus strains was investigated. Methods Between September, 2023 and January, 2024, a total of 200 specimens were collected from patients with suspected Staphylococcus aureus infections. Eighty-two isolates were identified as S. aureus from various sources, including wounds, nasal swabs, ear swabs, and blood, based on macroscopic, microscopic, and molecular properties. Biofilms were subjected to DNase and proteinase K treatment in order to identify their biochemical composition. Multiplex PCR was used to determine the distribution of sdr genes among isolates. Results The average reduction after treatment with proteinase K in MSSA biofilms (29.67±16.62) was significantly lower than in MRSA biofilms (46.21±26.33, p=0.032). Also, when treated with DNase, MRSA biofilms showed a greater average reduction (49.65±25.30) compared to MSSA biofilms (28.71±20.98, p=0.006). MRSA and MSSA biofilms also had different polysaccharide concentrations, with MSSA biofilms having significantly higher levels (206.86±82.92 μM/OD595) than MRSA biofilms (85.80±32.52 μM/OD595, p=0.005). The sdrC gene was most common in the gene profiles of MRSA (100%) and MSSA (50%). There was a strong association between the presence of the sdrD gene and methicillin-resistant S. aureus isolates (p < 0.001). Conclusion These findings indicate that the biofilms of MRSA isolates are largely composed of proteins and eDNA, while MSSA isolates rely on polysaccharides in their biofilms. The results indicate the importance of proteins encoded by SDR genes in the development of biofilm structure.

Biofilm targeting with chitosan-based nanohydrogel containing Quercus infectoria G. Olivier extract against Streptococcus mutans: new formulations of a traditional natural product

BackgroundBiofilm formation has a crucial role in the cariogenic virulence of Streptococcus mutans, which leads to resistance to common antibacterials. The antimicrobial resistance crisis has led to increased research about traditional natural products.PurposeQuercus infectoria extract (QI extract) and nano hydrogels containing QI extract (QI-NH) and tannic acid (TA-NH) were evaluated against this pathogen.MethodsQI extract was analyzed by HPLC and the physiological characteristics of nanohydrogels were assessed by SEM, FTIR, zeta potential, DLS and determination of release kinetics and encapsulation efficiency. Determination of MIC and MBC of the material and their anti-biofilm effect was done by the microtiter method and on the extracted tooth surface. The properties of extracts and nano hydrogels in the expression of genes codifying glucosyltransferases (gtfB, gtfC and gtfD) and glucan binding protein B (gbpB) were quantified. Their toxicity was tested by the MTT method against the KB cell line.ResultsAccording to HPLC, 55.18% of QI extract contained TA. The encapsulation efficiency of QI-NH and TA-NH was equal to 60% and 80%, respectively. SEM and FTIR exhibited that QI extract and TA were successfully entrapped in the networks resulting from the chemical bonding of chitosan and TPP. The average size of QI-NH and TA-NH was 70.45 and 58.43 nm, and their zeta potential was 6.17 ± 2.58 and 0.25 ± 0.03 mv, respectively. PDI < 0.3 of nano hydrogels indicated the favorable polydispersity of nanohydrogels. MIC of QI extract, QI-NH and TA-NH were 937.5, 30 and 10 µg/ml, respectively. Also their MBIC50 was 35.1, 2.1 and 0.95 µg/ml, respectively, and the extracts and nano hydrogels restrained the biofilm maturation on enamel. The pivotal genes of S. mutans in biofilm formation were significantly less expressed by treatment with QI-NH and TA-NH than others. Based on the MTT test, QI-NH had less acute toxicity than QI extract and TA-NH. IC50 of QI-NH was calculated as 775.4 µg/ml, while it was equal to 3.12 µg/ml for chlorhexidine as a common antibacterial agent.ConclusionQI-NH, a new formulation derived from traditional anti-caries, can be a safe and efficient option to combat dental biofilm.

Enhancing Antibacterial Efficacy: Combining Novel Bacterial Topoisomerase Inhibitors with Efflux Pump Inhibitors and Other Agents Against Gram-Negative Bacteria.

The novel bacterial topoisomerase inhibitors (NBTIs) developed in our laboratory show potent on-target enzyme inhibition but suffer from low activity against Gram-negative bacteria. With the aim of improving the antibacterial activity of our compounds against Gram-negative bacteria, we tested them in combination with different efflux pump inhibitors (EPIs), a strategy that showed promise in several other classes of antimicrobials. We also investigated the combined effect of NBTIs with ATP-competitive inhibitors of bacterial type II topoisomerases (ACIs), as well as the antibiofilm properties of our compounds and the combination with EPIs against early and mature Acietobacter baumannii biofilm. Our results demonstrate that combinations of NBTIs with EPI Phenylalanine-arginyl-β-naphthylamide significantly reduce the corresponding NBTIs' minimal inhibitory concentration values and show potentiation of A. baumannii biofilm inhibition as compared to NBTIs alone. Although combinations of NBITs and ACIs did not show synergistic effects, the FIC index value calculations revealed additive effects for all the combinations of a selected NBTI in combination with three ACIs in all the assayed Gram-negative bacteria from the ESKAPE group. These results show for the first time that combinations of NBTIs with either EPIs or a different class of the topoisomerase inhibitors may be a beneficial strategy to combat difficult-to-treat bacterial infections.

Temporin-Derived Peptides Disrupt the Exopolysaccharide Matrix of Streptococcus mutans to Prevent Related Dental Caries.

Dental caries, the most prevalent oral infectious disease, is closely associated with Streptococcus mutans. This study investigates the antimicrobial properties of the temporin-GHb peptide and its derivatives (GHbR, GHbK, and GHb3K) against S. mutans. These peptides exhibited potent anti-S. mutans activity through a membrane-disruptive mechanism, confirmed by flow cytometry and fluorescence staining assays while showing lower bactericidal effects on beneficial probiotic bacteria. Additionally, they inhibited the biofilm matrix formation by disrupting extracellular polysaccharide (EPS) synthesis, as demonstrated by zymography, qRT-PCR, and sucrose metabolism experiments. In a rat model of S. mutans-induced dental caries, treatment with these peptides significantly reduced the incidence of dental lesions. H&E staining analysis of rat oral tissues confirmed the biosafety of GHb and GHb3K. These findings suggest that temporin-derived peptides effectively target EPS, inhibiting biofilm formation and virulence, offering a promising strategy for preventing dental caries and promoting oral health. The findings suggest potential applications for peptide-based interventions to mitigate biofilm-related issues across various fields, including agriculture, food processing, and healthcare.

Mechanistic Insight into the Anti-Bacterial/Anti-Biofilm Effects of Low Chlorhexidine Concentrations on Enterococcus faecalis-In Vitro Study.

Endodontic treatment failures are often linked to the persistence of Enterococcus faecalis in the root canal system. This study aimed to investigate the antibacterial/antibiofilm mechanism of chlorhexidine (CHX), particularly at low concentrations, against E. faecalis, to improve endodontic treatment protocols. The antibacterial activity of CHX (0.125-20 μg/mL) was evaluated against E. faecalis ATCC 29212 using various assays, including planktonic growth inhibition, colony-forming units (CFUs), membrane permeability and potential assays, high-resolution scanning electron microscopy (HR-SEM), confocal laser scanning microscopy of biofilms, biomass and metabolic activity assays on matured biofilm, and quantitative real-time PCR for gene expression. Statistical analysis was performed using Student's t-test and ANOVA. CHX demonstrated concentration-dependent inhibition of E. faecalis, significantly reducing planktonic growth and CFUs. Membrane assays showed increased permeability and depolarization, indicating damage. HR-SEM revealed morphological changes, such as pore formation, while confocal microscopy showed a reduction in biofilm mass and extracellular substances. Gene expression analysis indicated the downregulation of virulence genes and upregulation of stress response genes. CHX at low concentrations disrupts E. faecalis at multiple levels, from membrane disruption to gene expression modulation, affecting mature biofilm. These findings support the refinement of endodontic disinfection protocols to reduce microbial persistence.

Quorum sensing regulation of Psl polysaccharide production by Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a common opportunistic pathogen and a model organism for studying bacterial sociality. A social behavior of P. aeruginosa that is critical for its success as a pathogen is its ability to form protective biofilms. Many of P. aeruginosa's social phenotypes are regulated by quorum sensing-a type of cell-cell communication that allows bacteria to respond to population density. Although biofilm formation is known to be affected by quorum sensing, evidence for direct regulation of biofilm production by quorum regulators has remained elusive. In this work, we show that production of the major biofilm matrix polysaccharide Psl in P. aeruginosa PAO1 is regulated by the quorum regulators LasR and RhlR in stationary-phase cultures. Secretion of Psl into the culture medium requires LasR, RhlR, and the quorum signal molecules N-3-oxo-dodecanoyl-homoserine lactone and N-butanoyl homoserine lactone. Psl production in strains unable to synthesize the homoserine lactone signals can be restored by exogenous introduction of the signal molecules. We found that LasR and RhlR perform different roles in the regulation of Psl production: LasR acts at the promoter of the psl operon and activates transcription of the Psl biosynthetic genes, while RhlR activates translation of the psl transcripts. This work contributes to our understanding of the overlapping but distinct functions of the Las and Rhl quorum-sensing systems and implicates both in the direct regulation of biofilm matrix production.IMPORTANCEPseudomonas aeruginosa biofilms are responsible for many treatment-resistant infections in humans. Many cooperative behaviors in P. aeruginosa are controlled by quorum sensing, but evidence for a direct role of quorum sensing in the regulation of biofilm matrix production has been scant. In this work, we show that the Las and Rhl quorum-sensing systems have distinct roles in regulating production of the matrix polysaccharide Psl and that this regulation happens at the level of transcription (Las) and translation (Rhl) of the psl operon. These findings deepen our understanding of overlapping functions of Las and Rhl quorum sensing and the complex regulation of biofilm development in P. aeruginosa.

Ginger Essential Oil Exerts Antibacterial Activity Against Shewanella putrefaciens by Disrupting Cell Structure and Resisting Biofilm

ABSTRACTThis study aimed to elucidate the antibacterial mechanism and antibiofilm activity of ginger essential oil (GEO) against Shewanella putrefaciens. On the basis of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), alkaline phosphatase (AKPase), succinate dehydrogenase (SDH), and glucose‐6‐phosphate dehydrogenase (G6PDH) activities were analyzed to evaluate the damage degree of S. putrefaciens on cell wall and membrane, and the microstructure was observed by scanning electron microscope (SEM) to evaluate the action effect against S. putrefaciens. The results showed that the MIC and MBC of GEO against S. putrefaciens were 27.8125 mg/mL and 55.625 mg/mL, respectively. The surface structures and cell membrane of S. putrefaciens were rigorously damaged by 1 MIC and 2 MIC GEO, leading to the leakage of cellular nucleic acids, protein, and β‐galactosidases from the bacterial cells. GEO could not only decrease the biomass of biofilm but also remove mature biofilm. In addition, GEO could reduce the production of exopolysaccharides and extracellular proteins, and could lessen the metabolic activity of biofilm cells. These results demonstrated that GEO exhibited efficient antibacterial characteristics against S. putrefaciens, which could act as a natural antibacterial and antibiofilm agent on the preservation of aquatic products.

Comparative analysis of biofilm structures in Salmonella Typhimurium DMC4 strain and its dam and seqA gene mutants using Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy methods.

It is well-established that the dam and seqA genes act in the biofilm production in Salmonella. However, the molecular basis underlying this activity remains unexplored. This study aims to address this gap in the literature. In this study, comparative Fourier Transform Infrared (FT-IR) Spectroscopy and Raman spectral analyses were conducted to investigate the molecular basis of decreases in swimming, swarming motility, and biofilm characteristics observed in the dam and seqA gene mutants of S. Typhimurium DMC4 wild-type strain. The comparative analysis revealed a pronounced reduction in proteins, lipids, carbohydrates, and nucleic acids within the biofilm structures of mutant strains. These findings confirm that these macromolecules are crucial for the integrity and functionality of biofilm structures. FT-IR analysis showed that while amide-I bands decreased in the biofilm structures of mutant strains, amide-II bands increased compared to the wild-type strain. Similarly, Raman analyses indicated an increase in amide-IV bonds and a decrease in amide-V bonds. The parallelism between FT-IR and Raman spectral analysis results, particularly regarding amide I, amide V, amide II, and amide IV bands, is noteworthy. Additionally, these findings may lead to the development of markers for rapidly diagnosing transitions from planktonic to biofilm form in Salmonella. The substantial decrease in β-glucans and lipids, including cellulose, within the biofilm matrix of mutant strains highlights the critical role these polymers play in swimming and swarming motility. Given the clinical and industrial importance of Salmonella biofilms, it is crucial to develop strategies to prevent biofilm formation and identify target molecules that can inhibit biofilm formation. The results of our study suggest that β-glucans and amides are essential targets in the effort to combat Salmonella biofilms.

5-Fluorouracil Inhibits Bacterial Growth and Reduces Biofilm in Addition to Having Synergetic Effects with Gentamicin Against Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a multidrug-resistant pathogen known for chronic infections, mainly due to biofilm formation. This study aimed to explore the potential repurposing of 5-fluorouracil (5-FU), an anticancer drug, to treat P. aeruginosa infections. Firstly, we investigated the inhibitory effects of 5-FU on bacterial growth using the microdilution method. Secondly, the impact of 5-FU on biofilm formation and disassembly was assessed via biofilm biomass measurements with the crystal violet staining method and confocal microscopy analyses. Lastly, the potential synergy between 5-FU and the antibiotics gentamicin and meropenem was evaluated using a checkerboard assay. Results revealed that 5-FU inhibited bacterial growth in a dose-dependent manner, with 100% inhibition observed at concentrations of 25 µg/mL and higher. Also, 70% and 100% reductions in biofilm biomass were demonstrated at concentrations of 12 and 100 µg/mL, respectively. Controversy, these higher concentrations unexpectedly increased biofilm biomass in pre-formed biofilms. Synergistic interactions were observed between 5-FU and gentamicin in both growth inhibition (FICI 0.31) and biofilm inhibition (ZIP 14.1), while no synergy was found with meropenem. These findings highlight the potential of 5-FU as an adjunctive therapy for P. aeruginosa infections, especially in combination with gentamicin. However, further research is required to address 5-FU limitations against mature biofilms.

Simvastatin Efficacy on Endodontic Biofilms: An In Vitro Study.

Mature biofilms were grown on dentin specimens and put in contact with the solutions to determine their antibiofilm activity. To assess residual antimicrobial activity, the dentin samples were immersed for 5 min in the solutions before microbial infection for 3 weeks. The study groups were: (1) 8% SIM, (2) 4% SIM, (3) 4% DC, (4) 2.5% sodium hypochlorite (NaOCl), and (5) 0.9% saline solution (SS). Cell viability was evaluated by means of the adenosine triphosphate (ATP) assay and flow cytometry (FC). The data collected were analyzed with the ANOVA test using Welch's correction followed by the Games-Howell test. The level of statistical significance was p < 0.05, and statistical analysis was performed using SPSS 23.0. All study groups reduced the biofilms significantly with respect to the control. The highest reduction percentage was obtained by 2.5% NaOCl, followed by SIM 8% and 4%, without statistically significant differences. In terms of residual activity, the 4% DC solution obtained a higher percentage of dead cells. Solutions of 4% and 8% SIM, and 4% Diclofenac, show antimicrobial and residual activity against multispecies endodontic biofilms.

Evaluating the Efficacy of Ɛ-poly-lysine, Hydrogen Peroxide, and Lauric Arginate to Inhibit Listeria monocytogenes Biofilm Formation and Inactivate Mature Biofilms

Preventing the introduction of Listeria monocytogenes, subsequent biofilm formation, and persistence in food processing environments is important for reducing the risk of cross-contamination of ready-to-eat foods. This study determined the effect of Ɛ-poly-lysine (EPL), hydrogen peroxide (HP), and lauric arginate (LAE) on L. monocytogenes biofilm formation and the inactivation of mature biofilms. For inhibition studies, biofilms of L. monocytogenes Scott A (serotype 4b) and 2014L-6025 (1/2b) were developed separately at 37 °C for 48 h in the presence of sub-inhibitory concentrations (SIC) of either EPL (10 ppm), HP (2 ppm), or LAE (1.5 ppm) on polystyrene plates and stainless-steel rounds. Inactivation was determined by exposing mature biofilms on each surface to each antimicrobial at their minimum bactericidal concentration (MBC), 10xMBC, or 100xMBC for 24 h at 37 °C. The presence of these antimicrobials at SIC did not inhibit biofilm formation on either surface and their effect on mature biofilms varied by strain and surface. Application of EPL at 1xMBC (100 ppm) for 24 h resulted in greater reductions in counts of both strains on polystyrene than HP (40 ppm) and LAE (5 ppm) under the same conditions at 1xMBC (P ≤ 0.0243). Exposure of mature biofilms to LAE at 10xMBC (50 ppm) for 1 h was more effective in reducing counts on polystyrene than HP at 10xMBC (400 ppm) for the same duration (P ≤ 0.0136), and both HP and LAE applied at 100xMBC (4,000 and 500 ppm, respectively) for 24 h more effectively inactivated mature biofilms of L. monocytogenes Scott A on polystyrene compared to EPL (10,000 ppm) (P ≤ 0.0307). Application of LAE at 10xMBC for 24 h was more effective at inactivating strain Scott A on stainless steel compared to 10xMBC of EPL (1,000) or HP (P ≤ 0.0430). Future studies are needed to determine the efficacy of these and other antimicrobials on additional strains and serotypes of L. monocytogenes at temperatures relevant to food production and storage.