Wound Biofilm Research Articles

Association of biofilm and microbial metrics with healing rate in older adults with chronic venous leg ulcers.

The presence of microbial biofilms in many human chronic wounds led to the hypothesis that biofilms delay healing of these wounds. We tested this hypothesis in a population of 117 older individuals with venous leg ulcers who were receiving standardised therapy, including frequent debridement. Debridement specimens were analysed for the amount of bacterial biomass by two independent methods: a microscopic approach that scored the relative size and number of bacterial aggregates, interpreted as a biofilm metric, and conventional enumeration by agar plating for viable bacteria. The plating protocol yielded three distinct values: the total viable bacterial count, bleach-tolerant bacteria, and the log reduction in viable bacteria upon bleach treatment. Wound healing rates over an 8-week observation period were calculated as the rate of decrease of the equivalent diameter of the wound. There was no statistically significant association between wound healing and the biofilm metric in any of the three analyses performed (p ≥0.15). In all three statistical tests, wound healing was associated with the log reduction caused by bleach treatment (p ≤0.004); wounds that harboured bacteria that were more bleach-susceptible healed more slowly. A refinement of the model of chronic wound infection pathogenesis is proposed in which dormant bacteria constitute a persistent nidus and outgrowth of metabolically active cells impairs healing. This model constitutes a new hypothesis as metabolic activity was not directly measured in this investigation.

Biofilms and Microbiome Profiles in Chronic Wounds: Links to Antibiotic Use and Wound Severity in a Sri Lankan Cohort.

We have characterized the microbiome of infected chronic diabetic wounds (CDWs), exploring associations with antibiotic use and wound severity in a Sri Lankan cohort. Fifty CDW patients were enrolled, 38 of whom received antibiotics. Tissue biopsies were analyzed by microbiome profiling, and wounds were graded using the University of Texas Wound Grading System. Biofilm presence was assessed in 20 wounds. The microbiome was largely dominated by Enterobacteriaceae, Pseudomonadaceae, Streptococcaceae, and Corynebacteriaceae. Proteobacteria levels were significantly higher in antibiotic-treated wounds (p=0.019), with increased Pseudomonas abundance. Wounds were categorized as grade 1 (10), grade 2 (29), and grade 3 (11). Alpha diversity varied by wound grade (p=0.015), with grade 2 wounds showing the highest diversity and grade 3 the lowest. All 20 tested wounds were biofilm-positive, and community composition varied more in antibiotic-treated wounds (p=0.004). CDW microbiomes were dominated by Enterobacteriaceae and Pseudomonadaceae, with elevated Proteobacteria in antibiotic-treated wounds. Alpha diversity correlated with wound severity, peaking in grade 2 wounds. The high prevalence of biofilms in wounds underscores the need for management of CDWs that address microbial complexity.

In-vitro anti-acne activity of Teucrium oliverianum methanolic extract against Cutibacterium acnes.

Acne vulgaris is a skin infection widely seen in adolescents between 10-19years with males affected more than females. It mainly affects the face but may also affect the back and chest. The symptoms vary with mild acne manifesting as comedones and moderate acne as inflammatory lesions (papulopustular), nodules, and mild scarring while severe acne has the same symptoms that have not subsided within 6months of treatment. Various treatments including topical medications containing different antibiotics are used to treat acne. Recently, herbal treatments have been shown as better alternatives to conventional treatment. Teucrium oliverianum Ging. ex Benth (Lamiaceae) is traditionally used for skin infections such as wound healing and biofilm formation. Methanolic extract of T. oliverianum was subjected to liquid chromatography-mass spectrometry (LC-MS) analysis, and its antibacterial effect against Cutibacterium acnes. The anti-acne, anti-inflammatory, and antioxidant effects were also assessed using HaCaT cells infected with C. acnes. The cytotoxicity of the extract was evaluated using a neutral red uptake assay, and anti-inflammatory effects were determined by measuring TNF-α, IL-1β, INF-γ, and COX2 inhibition. The antioxidant action was assessed by ROS generation in HaCaT cells infected with C. acnes. LC-MS analysis of the extract showed the presence of 16 different metabolites with L-carnitine, esculin sesquihydrate, and gamma-linoleic acid as major metabolites. The methanolic extract of T. oliverianum showed an antibacterial effect against C. acnes with an IC50 value of 263.2μg/mL. The extract attenuated the cytotoxicity of C. acnes on the HaCaT cell and the IC50 was found to be 676.2μg/mL. It also decreased dose-dependently the expression of TNF-α, IL-1β, INF-γ, and inhibited COX2 in the HaCaT cells infected with C. acnes. It also decreased the generation of reactive oxygen species. The results support the use of T. oliverianum as an anti-acne agent but it possesses mild antibacterial action. It showed anti-inflammatory effects in HaCaT cells infected with C. acnes. It is also an effective antioxidant and decreased the generation of reactive oxygen species. Comparison of the anti-acne effects and adverse reactions of extract with other treatments will provide more insight into its clinical efficacy and toxicity.

Multifunctional NIR-II nanoplatform for disrupting biofilm and promoting infected wound healing

Healing wounds presents a significant challenge due to bacterial biofilm infections and the inherent drug resistance of these biofilms. This report introduces a multifunctional nanoplatform (NPs) designed to combat wound biofilm infections using NIR-II photothermal therapy. The NPs are self-assembled from amphiphilic polymers (AP) to encapsulate photothermal polymers (PT) through classic electrostatic interactions. Importantly, these NPs are electrically neutral, which enhances their ability to penetrate biofilms effectively. Once inside the biofilm, the NPs achieve complete thermal ablation of the biofilm under NIR-II laser irradiation. Additionally, when exposed to laser and the GSH microenvironment, the NPs exhibit strong photothermal effects and self-degradation capabilities. In vitro tests confirm that the NPs have excellent antibacterial and anti-biofilm properties against methicillin-resistant Staphylococcus aureus (MRSA). In vivo studies demonstrate that the NPs can efficiently clear wound biofilm infections and promote wound healing. Notably, the NPs show superior photothermal effects under NIR-II laser irradiation compared to NIR-I lasers. In summary, the developed NPs serve as an integrated diagnostic and therapeutic nano-antimicrobial agent, offering promising applications for biofilm wound infections and wound healing.

Assessment of the Antibiofilm Performance of Silver-Containing Wound Dressings: A Dual-Species Biofilm Model.

Background It is commonly accepted that microorganisms found within hard-to-heal wounds are present in biofilm form. Biofilms are often polymicrobial in nature, which increases their virulence and tolerance to antimicrobial agents. The aim of this study was to compare the antibiofilm activity of silver-containing antimicrobial wound dressings in a dual-species simulated wound biofilm model. Materials and methods Four silver-containing wound dressings were evaluated in vitro: Aquacel® Ag+ Extra™ dressing, KerraContact® Ag dressing, Durafiber* Ag dressing, and UrgoClean Ag dressing. Each dressing was applied to a simulated wound assembly containing biofilm-gauze inoculated with Klebsiella pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA). Each biofilm-inoculated gauze was incubated at 35±3ºC for 6, 24, 48 and 72 hours. Enumeration of surviving biofilm bacteria at each time point was performed in triplicate for each test dressing and its equivalent control. Results Aquacel® Ag+ Extra™ dressing was observed to reduce the biofilm population within 24 hours with a >4 log10 kill observed for K. pneumoniae and >6 log10 for MRSA from an initial biofilm challenge of 4.16×109 CFU/mL. This kill rate was sustained for the duration of the challenge period, with Aquacel®Ag+ Extra™ dressing reducing the biofilm population to non-detectable levels (<30 Colony Forming Units (CFU) per test) by 72 hours for K. pneumoniae and by 48 hours for MRSA. KerraContact® Ag dressing demonstrated an initial reduction at 6 hours of ~2 log10 in both K. pneumoniae and MRSA. Durafiber* Ag dressing exhibited a slight, gradual reduction in biofilm population over the course of the test period, reducing each challenge organism by ~2.5 log10 by 72 hours. UrgoClean Ag was shown to have little to no impact on the dual-species biofilm with levels remaining similar or greater than that recovered prior to dressing application. The no-dressing biofilm-colonised gauze control demonstrated that the biofilm bacteria remained viable throughout the test period and species population proportionality was maintained. Conclusion Using a dual-species simulated wound biofilm model comprising the pathogens K. pneumoniae and MRSA, Aquacel® Ag+ Extra™ dressing demonstrated significantly greater antibiofilm activity than the other silver-containing dressings. The enhanced antibiofilm activity of Aquacel® Ag+ Extra™ dressing in this study may be attributed to the additional antibiofilm agents, ethylenediaminetetraacetic acid and benzethonium chloride, contained within the dressing.

Assessing Biofilm at the Bedside: Exploring Reliable Accessible Biofilm Detection Methods.

Biofilm is linked through a variety of mechanisms to the pathogenesis of chronic wounds. However, accurate biofilm detection is challenging, demanding highly specialized and technically complex methods rendering it unapplicable for most clinical settings. This study evaluated promising methods of bedside biofilm localization, fluorescence imaging of wound bacterial loads, and biofilm blotting by comparing their performance against validation scanning electron microscopy (SEM). In this clinical trial, 40 chronic hard-to-heal wounds underwent the following assessments: (1) clinical signs of biofilm (CSB), (2) biofilm blotting, (3) fluorescence imaging for localizing bacterial loads, wound scraping taken for (4) SEM to confirm matrix encased bacteria (biofilm), and (5) PCR (Polymerase Chain Reaction) and NGS (Next Generation Sequencing) to determine absolute bacterial load and species present. We used a combination of SEM and PCR microbiology to calculate the diagnostic accuracy measures of the CSB, biofilm blotting assay, and fluorescence imaging. Study data demonstrate that 62.5% of wounds were identified as biofilm-positive based on SEM and microbiological assessment. By employing this method to determine the gold truth, and thus calculate accuracy measures for all methods, fluorescence imaging demonstrated superior sensitivity (84%) and accuracy (63%) compared to CSB (sensitivity 44% and accuracy 43%) and biofilm blotting (sensitivity 24% and accuracy 40%). Biofilm blotting exhibited the highest specificity (64%), albeit with lower sensitivity and accuracy. Using SEM alone as the validation method slightly altered the results, but all trends held constant. This trial provides the first comparative assessment of bedside methods for wound biofilm detection. We report the diagnostic accuracy measures of these more feasibly implementable methods versus laboratory-based SEM. Fluorescence imaging showed the greatest number of true positives (highest sensitivity), which is clinically relevant and provides assurance that no pathogenic bacteria will be missed. It effectively alerted regions of biofilm at the point-of-care with greater accuracy than standard clinical assessment (CSB) or biofilm blotting paper, providing actionable information that will likely translate into enhanced therapeutic approaches and better patient outcomes.

Engineered Bacteriophage-Polymer Nanoassemblies for Treatment of Wound Biofilm Infections.

The antibacterial efficacy and specificity of lytic bacteriophages (phages) make them promising therapeutics for treatment of multidrug-resistant bacterial infections. Restricted penetration of phages through the protective matrix of biofilms, however, may limit their efficacy against biofilm infections. Here, engineered polymers were used to generate noncovalent phage-polymer nanoassemblies (PPNs) that penetrate bacterial biofilms and kill resident bacteria. Phage K, active against multiple strains of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), was assembled with cationic poly(oxanorbornene) polymers into PPNs. The PPNs retained phage infectivity, while demonstrating enhanced biofilm penetration and killing relative to free phages. PPNs achieved 3-log10 bacterial reduction (∼99.9%) against MRSA biofilms in vitro. PPNs were then incorporated into Poloxamer 407 (P407) hydrogels and applied onto in vivo wound biofilms, demonstrating controlled and sustained release. Hydrogel-incorporated PPNs were effective in a murine MRSA wound biofilm model, showing a 1.5-log10 reduction in bacterial load compared to a 0.5 log reduction with phage K in P407 hydrogel. Overall, this work showcases the therapeutic potential of phage K engineered with cationic polymers for treating wound biofilm infections.

PCL-gelatin honey scaffolds promote Staphylococcus aureus agrA expression in biofilms with Pseudomonas aeruginosa.

Bacterial infection and biofilm formation contribute to impaired healing in chronic diabetic wounds. Staphylococcus aureus and Pseudomonas aeruginosa are found in human diabetic wound biofilms. They may develop antibiotic resistance, increasing the urgency for alternative or complementary therapies. Diabetic wound healing may be improved with the use of biomedically engineered scaffolds, which can also serve as delivery systems for antibacterial compounds. Manuka honey is a potent antibacterial and wound care agent due to its high osmolarity, low pH, and constituents (such as methylglyoxal). Honey exhibits bacteriostatic and bactericidal effects, modulates the expression of biofilm forming genes, and restores antibiotic susceptibility in previously drug resistant pathogens. In this study, we created a dermal regeneration template (DRT) composed of polycaprolactone-gelatin (PCL-gelatin) and Manuka honey to retain honey in the wound and also provide a scaffold for tissue regeneration. Soluble Manuka honey inhibited the planktonic and biofilm growth of both S. aureus (UWH3) and P. aeruginosa (PA14) co-cultures. Manuka honey embedded PCL-gelatin scaffolds did not exhibit bacteriostatic or bactericidal effects on cocultures of UHW3 and PA14; however, they promoted the expression of AgrA, a gene associated with dispersal of S. aureus biofilms.

Antibacterial properties of photo-crosslinked chitosan/methacrylated hyaluronic acid nanoparticles loaded with bacitracin

The current treatments for wounds often fail to induce adequate healing, leaving wounds vulnerable to persistent infections and development of drug-resistant microbial biofilms. New natural-derived nanoparticles were studied to impair bacteria colonization and hinder the formation of biofilms in wounds. The nanoparticles were fabricated through polyelectrolyte complexation of chitosan (CS, polycation) and hyaluronic acid (HA, polyanion). UV-induced photo-crosslinking was used to enhance the stability of the nanoparticles. To achieve this, HA was methacrylated (HAMA, degree of modification of 20 %). Photo-crosslinked nanoparticles obtained from HAMA and CS had a diameter of 478 nm and a more homogeneous size distribution than nanoparticles assembled solely through complexation (742 nm). The nanoparticles were loaded with the antimicrobial agent bacitracin (BC), resulting in nanoparticles with a diameter of 332 nm. The encapsulation of BC was highly efficient (97 %). The BC-loaded nanoparticles showed significant antibacterial activity against gram-positive bacteria Staphylococcus aureus, Methicillin-resistant S. aureus and S. epidermidis. Photo-crosslinked HAMA/CS nanoparticles loaded with BC demonstrated inhibition of biofilm formation and a positive effect on the proliferation of mammalian cells (L929). These crosslinked nanoparticles have potential for the long-term treatment of wounds and controlled antibiotic delivery at the location of a lesion.

Antibiotic Alternatives: Multifunctional Ultra-Small Metal Nanoclusters for Bacterial Infectious Therapy Application.

The prevalence of major bacterial infections has emerged as a significant menace to human health and life. Conventional treatment methods primarily rely on antibiotic therapy, but the overuse of these drugs has led to a decline in their efficacy. Moreover, bacteria have developed resistance towards antibiotics, giving rise to the emergence of superbugs. Consequently, there is an urgent need for novel antibacterial agents or alternative strategies to combat bacterial infections. Nanoantibiotics encompass a class of nano-antibacterial materials that possess inherent antimicrobial activity or can serve as carriers to enhance drug delivery efficiency and safety. In recent years, metal nanoclusters (M NCs) have gained prominence in the field of nanoantibiotics due to their ultra-small size (less than 3 nm) and distinctive electronic and optical properties, as well as their biosafety features. In this review, we discuss the recent progress of M NCs as a new generation of antibacterial agents. First, the main synthesis methods and characteristics of M NCs are presented. Then, we focus on reviewing various strategies for detecting and treating pathogenic bacterial infections using M NCs, summarizing the antibacterial effects of these nanoantibiotics on wound infections, biofilms, and oral infections. Finally, we propose a perspective on the remaining challenges and future developments of M NCs for bacterial infectious therapy.

Staphylococcus pseudintermedius and Pseudomonas aeruginosa Lubbock Chronic Wound Biofilm (LCWB): a suitable dual-species model for in vitro studies

Antimicrobial treatment of methicillin-resistant Staphylococcus pseudintermedius associated with canine wounds represents an important challenge. The aim of this study was to create a canine wound infection model, Lubbock Chronic Wound Biofilm (LCWB), with a focus on S. pseudintermedius, drawing inspiration from the established human model involving Staphylococcus aureus. Methicillin-resistant S. pseudintermedius 115 (MRSP) and Pseudomonas aeruginosa 700 strains, isolated from dog wounds, were used to set up the LCWB at 24, 48 and 72 h. The LCWBs were evaluated in terms of volume, weight, and microbial CFU/mg. The microbial spatial distribution in the LCWBs was assessed by SEM and CLSM imaging. The best incubation time for the LCWB production in terms of volume (3.38 cm3 ± 0.13), weight (0.86 gr ± 0.02) and CFU/mg (up to 7.05 × 106 CFU/mg ± 2.89 × 105) was 48 h. The SEM and CLSM images showed a major viable microbial colonization at 48 h with non-mixed bacteria with a prevalence of MRSP on the surface and P. aeruginosa 700 in the depth of the wound. The obtained findings demonstrate the capability of S. pseudintermedius to grow together P. aeruginosa in the LCWB model, representing the suitable model to reproduce the animal chronic wound in vitro.

Nano‐Fat Actuated Lipometabolic Reprogramming of Macrophages for Intracellular Infections in Biofilm Microenvironment

AbstractMetabolic competition is a zero‐sum game between bacterial biofilms and host immune responses on the surface of medical implants. In an in vitro biofilm‐macrophages co‐culture system, it is found that suppressed lipid metabolic processes in host macrophages in the biofilm microenvironment correlates with immune tolerance and intracellular persistence. Reactivation of immune cells against bacterial infection by reprogramming lipid metabolism through the supply of lipids such as oleic acid (OA) is a promising strategy, but this cannot completely destroy the bacterial biofilms. Nanomaterial‐based zinc ion interference therapy in antibacterial field emerges relying on the outstanding benefits of nanomaterials. Therefore, a targeted nano‐fat HSA‐IR820@OA@ZIF‐8 (HIROZ) with near infrared‐II (NIR‐II) photothermal capacities is developed for the destrcution of the biofilms via zinc ion combined photothermal therapy. The improved cellular compatibility and enhanced intracellular uptake make HIROZ induce intracellular lipid droplets (LDs) formation in macrophages. Photothermal combined zinc ion‐induced metabolic interference augments the antimicrobial effect of LDs and activates lipometabolic reprogramming‐mediated antibacterial immune responses via mitochondrial stress. In the mouse wound biofilm infections model and subcutaneous implant‐associated biofilm infections (IABIs) model, HIROZ demonstrates sustained and thorough biofilm scavenging based on reprogramming of lipid metabolism, providing a new idea for metabolic interference‐centered therapeutic strategies for full‐scale IABIs eliminations.

Bacterial lipase-responsive polydopamine nanoparticles for detection and synergistic therapy of wound biofilms infection

Wound biofilms represent an elusive conundrum in contemporary treatment and diagnostic options, accredited to their escalating antibiotic resistance and interference in chronic wound healing processes. Here, we developed mesoporous polydopamine (mPDA) nanoparticles, and grafted with rhodamine B (Rb) as biofilm lipase responsive detection probe, followed by π − π stacking mediated ciprofloxacin (CIP) loading to create mP-Rb@CIP nanoparticles. mPDA NPs with a melanin structure could quench fluorescence emissions of Rb. Once encountering biofilm in vivo, the ester bond in Rb and mPDA is hydrolyzed by elevated lipase concentrations, triggering the liberation of Rb and restore fluorescence emissions to achieve real-time imaging of biofilm-infected wounds. Afterwards, the 808 nm near-infrared (NIR) illumination initiates a spatiotemporal controlled antibacterial photothermal therapy (PTT), boosting its effectiveness through photothermal-triggered CIP release for synergistic biofilm eradication. The mP-Rb@CIP platform exhibits dual diagnostic and therapeutic functions, efficaciously treating biofilm-infected wounds in vivo and in vitro. Particularly, the mP-Rb@CIP/NIR procedure expedites wound-healing by alleviating oxidative stress, modulating inflammatory mediators, boosting collagen synthesis, and promoting angiogenesis. Taken together, the theranostic nanosystem strategy holds significant potential for addressing wound biofilm-associated infections.

Accelerated infected wound healing by probiotic-based living microneedles with long-acting antibacterial effect

Delays in infected wound healing are usually a result of bacterial infection and local inflammation, which imposes a significant and often underappreciated burden on patients and society. Current therapies for chronic wound infection generally suffer from limited drug permeability and frequent drug administration, owing to the existence of a wound biofilm that acts as a barrier restricting the entry of various antibacterial drugs. Here, we report the design of a biocompatible probiotic-based microneedle (MN) patch that can rapidly deliver beneficial bacteria to wound tissues with improved delivery efficiency. The probiotic is capable of continuously producing antimicrobial substances by metabolizing introduced glycerol, thereby facilitating infected wound healing through long-acting antibacterial and anti-inflammatory effects. Additionally, the beneficial bacteria can remain highly viable (>80 %) inside MNs for as long as 60 days at 4 °C. In a mouse model of Staphylococcus aureus-infected wounds, a single administration of the MN patch exhibited superior antimicrobial efficiency and wound healing performance in comparison with the control groups, indicating great potential for accelerating infected wound closure. Further development of live probiotic-based MN patches may enable patients to better manage chronically infected wounds.

Transpiration-Inspired Fabric Dressing for Acceleration Healing of Wound Infected with Biofilm.

In chronic wound management, efficacious handling of exudate and bacterial infections stands as a paramount challenge. Here a novel biomimetic fabric, inspired by the natural transpiration mechanisms in plants, is introduced. Uniquely, the fabric combines a commercial polyethylene terephthalate (PET) fabric with asymmetrically grown 1Drutile titanium dioxide (TiO2) micro/nanostructures, emulating critical plant features: hierarchically porous networks and hydrophilic water conduction channels. This structure endows the fabric with exceptional antigravity wicking-evaporation performance, evidenced by a 780% one-way transport capability and a 0.75g h-1 water evaporation rate, which significantly surpasses that of conventional moisture-wicking textiles. Moreover, the incorporated 1D rutile TiO2 micro/nanostructures present solar-light induced antibacterial activity, crucial for disrupting and eradicating wound biofilms. The biomimetic transpiration fabric is employed to drain exudate and eradicate biofilms in Staphylococcus aureus (S. aureus)-infected wounds, demonstrating a much faster infection eradication capability compared to clinically common ciprofloxacin irrigation. These findings illuminate the path for developing high-performance, textile-based wound dressings, offering efficient clinical platforms to combat biofilms associated with chronic wounds.

Optimization of ultrasound contrast agent and treatment duration for drug delivery to methicillin-resistant Staphylococcus aureus diabetic wound biofilms in mice

Chronic wounds are frequently infected with bacterial biofilms which pose a barrier to drug diffusion, drug uptake, and facilitate drug tolerance, thereby prolonging the healing process in chronic wounds and increasing the likelihood of relapse. A major contributor to relapse is persister cells, a subset resilient to high antibiotic doses. Previous work by our group showcased significantly improved gentamicin efficacy in a diabetic murine wound model using ultrasound, nanodroplets, and an anti-persister drug. Here, we aim to optimize nanodroplet formulation for persister cell targeting and treatment duration for clinical translation. In a methicillin-resistant Staphylococcus aureus (MRSA) diabetic wound model in SKH-1 hairless mice (n = 5), wounds were treated twice daily with gentamicin, ultrasound, and nanodroplets containing oxygen or palmitoleic acid (PA). These components aim to increase oxygenation and enhance persister uptake, respectively. Additionally, treatments with gentamicin, PA nanodroplets, and ultrasound for 2, 5, and 10 minutes were investigated (n = 3). Preliminary findings indicate PA most effectively potentiates antibiotic activity, 10- minute treatments improve efficacy by 1-log compared to 5-minutes, and 2-minute treatments achieve comparable efficacy to 5-minutes. These initial findings suggest a promising strategy for enhancing antibiotic efficacy and targeting persister cells in biofilms, with consideration for resource-efficient treatment times for clinical application.

Development, characterization, and evaluation of a simple polymicrobial colony biofilm model for testing of antimicrobial wound dressings.

Simple biofilm models are the first step to testing of any antimicrobial and wound dressing; therefore, the aim of this study was to develop and validate a simple polymicrobial colony biofilm wound model comprised of Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans on RPMI-1640 agar. The model was then used to evaluate the topical disinfectant chlorohexidine and four commercially available wound dressings using the polymicrobial model. The model used was as a starting point to mimic debridement in clinical care of wounds and the effectiveness of wound dressings evaluated afterwards. Planktonic assessment using AATCC100-2004 demonstrated that all antimicrobial wound dressings reduced the planktonic microbial burden below the limit of detection; however, when challenged with polymicrobial colony biofilms, silver wound dressings showed limited effectiveness (1-2 log CFU reductions). In contrast, a single iodine releasing wound dressing showed potent antibiofilm activity reducing all species CFUs below the limit of detection (>6-10 log) depending on the species. A disrupted biofilm model challenge was performed to represent the debridement of a wound and wound silver-based wound dressings were found to be marginally more effective than in whole colony biofilm challenges while the iodine containing wound dressing reduced microbial recovery below the limit of detection. In this model, silver dressings were ineffective versus the whole colony biofilms but showed some recovery of activity versus the disrupted colony biofilm. The iodine wound dressing reduced the viability of all species below the level of detection. This suggests that mode of action of wound dressing should be considered for the type of biofilm challenge as should the clinical use, e.g. debridement.

Strong Activity and No Resistance Induction Exerted by Cell-Free Supernatants from Lacticaseibacillus rhamnosus against Mono-Species and Dual-Species Biofilms of Wound Pathogens in In Vivo-like Conditions.

It is widely agreed that microbial biofilms play a major role in promoting infection and delaying healing of chronic wounds. In the era of microbial resistance, probiotic strains or their metabolic products are emerging as an innovative approach for the treatment of hard-to-heal (chronic) wounds due to their antimicrobial, healing, and host immune-modulatory effects. In this study, we aimed to investigate the potential of cell-free supernatants (CFS) from Lacticaseibacillus rhamnosus GG against mono- and dual-species biofilms of wound pathogens in a 3D in vitro infection model. Mature biofilms of Pseudomonas aeruginosa and Staphylococcus aureus were obtained on collagen scaffolds in the presence of a simulant wound fluid (SWF) and treated with CFS at different doses and time intervals. At 1:4 dilution in SWF, CFS caused a marked reduction in the colony forming-unit (CFU) numbers of bacteria embedded in mono-species biofilms as well as bacteria released by the biofilms in the supernatant. CFU count and electron microscopy imaging also demonstrated a marked antibiofilm effect against dual-species biofilms starting from 8 h of incubation. Furthermore, CFS exhibited acceptable levels of cytotoxicity at 24 h of incubation against HaCaT cells and, differently from ciprofloxacin, failed to induce resistance after 15 passages at sub-inhibitory concentrations. Overall, the results obtained point to L. rhamnosus GG postbiotics as a promising strategy for the treatment of wound biofilms.

An objective comparative study of non-surgical cleansing techniques and cleanser types in bacterial burden management.

Cleansing is a vital component of effective wound hygiene and biofilm management, often accomplished through vigorous mechanical action or through soaking with moistened gauze. In the present study, a quantitative comparison of the effectiveness of different cleansing techniques and solutions in removing bacteria was conducted on 71 chronic wounds using bacterial fluorescence imaging as a real-time diagnostic for moderate to high bacterial loads. Vigorous gauze cleansing for 30 s proved most effective by reducing bacterial fluorescence by 33.99%, surpassing 10-min soaking in bacterial reduction (13.24%). Among different cleansers, no statistically significant differences in effectiveness were observed, but povidone-iodine showed the strongest trend towards bacterial reduction. Sub-analysis highlighted the superiority of antiseptic cleansers over saline and gentle soap (-33.30% vs. -1.80% bacterial reduction respectively). Five percent acetic acid was also shown to be more effective in removing specific bacterial strains (Pseudomonas aeruginosa). Findings from studies like this contribute to refining wound hygiene guidelines and clinical algorithms for bacterial and biofilm management.

Multi-targeting oligopyridiniums: Rational design for biofilm dispersion and bacterial persister eradication

The development of effective antibacterial drugs to combat bacterial infections, particularly the biofilm-related infections, remains a challenge. There are two important features of bacterial biofilms, which are well-known critical factors causing biofilms hard-to-treat in clinical, including the dense and impermeable extracellular polymeric substances (EPS) and the metabolically repressed dormant and persistent bacterial population embedded. These characteristics largely increase the difficulty for regular antibiotic treatment due to insufficient penetration into EPS. In addition, the dormant bacteria are insensitive to the growth-inhibiting mechanism of traditional antibiotics. Herein, we explore the potential of a series of new oligopyridinium-based oligomers bearing a multi-biomacromolecule targeting function as the potent bacterial biofilm eradication agent. These oligomers were rationally designed to be “charge-on-backbone” that can offer a special alternating amphiphilicity. This novel and unique feature endows high affinity to bacterial membrane lipids, DNAs as well as proteins. Such a broad multi-targeting nature of molecules not only enables its penetration into EPS, but also plays vital roles in the bactericidal mechanism of action that is highly effective against dormant and persistent bacteria. Our in vitro, ex vivo, and in vivo studies demonstrated that OPc3, one of the most effective derivatives, was able to offer excellent antibacterial potency against a variety of bacteria and effectively eliminate biofilms in zebrafish models and mouse wound biofilm infection models.