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Objective: Wound dressings that inactivate or sequestrate microorganisms, such as those with a hydrophobic, bacteria-binding dialkylcarbamoyl chloride (DACC) surface, can reduce the risk of clinical infections. This 'passive' bioburden control, avoiding bacterial cell wall disruption with associated release of bacterial endotoxins aggravating inflammation, is advantageous in hard-to-heal wounds. Hence, the full scope of DACC dressings, including the potential impact of higher inoculum densities, increased protein load and different pH on antibacterial activity, needs to be evaluated., Method: The Japanese Industrial Standard (JIS) L 1902 challenge test was used to evaluate the antimicrobial activity of the DACC-coated dressing against several World Health Organization (WHO)-prioritised wound pathogens (e.g., meticillin-resistant Staphylococcus aureus , vancomycin-resistant Enterococcus , microorganisms with extended-spectrum beta-lactamases and Acinetobacter baumannii ), the effect of repeated bacterial challenge in an adverse wound environment, and antimicrobial performance at wound-related pH., Results: High antibacterial activity of the DACC-coated dressing against the WHO-prioritised bacteria strains by its irreversible binding and inhibition of growth of bound bacteria was confirmed using JIS L 1902. At increased inoculation densities, compared to standard conditions, the DACC-coated dressing still achieved strong-to-significant antibacterial effects. Augmenting the media protein content also affected antibacterial performance; a 0.5-1 log reduction in antibacterial activity was observed upon addition of 10% fetal calf serum. The pH did not influence antibacterial performance. The DACC-coated dressing also sustained antibacterial activity over subsequent reinfection steps., Conclusion: It can be assumed that the DACC-coated dressing exerts beneficial effects in controlling the wound bioburden, reducing the overall demand placed on antibiotics, without using antimicrobial substances.

Objective: Endotoxin causes inflammation and can impair wound healing. Conventional methods that reduce bioburden in wounds by killing microorganisms using antibiotics, topical antimicrobials or antimicrobial dressings may induce endotoxin release from Gram-negative bacteria. Another approach is to reduce bioburden by adsorbing microorganisms, without killing them, using dialkylcarbamoyl chloride (DACC)-coated wound dressings. This study evaluated the endotoxin-binding ability of a DACC-coated wound dressing (Sorbact Compress, Abigo Medical AB, Sweden) in vitro, including its effect on the level of natural endotoxin released from Gram-negative bacteria., Method: Different concentrations of purified Pseudomonas aeruginosa endotoxin and a DACC-coated dressing were incubated at 37°C for various durations. After incubation, the dressing was removed and endotoxin concentration in the solution was quantified using a Limulus amebocyte lysate (LAL) assay. The DACC-coated dressing was also incubated with Pseudomonas aeruginosa cells for one hour at 37°C. After incubation, the dressing and bacterial cells were removed and shed endotoxin remaining in the solution was quantified., Results: Overnight incubation of the DACC-coated wound dressing with various concentrations of purified Pseudomonas aeruginosa endotoxin (96-11000 EU/ml) consistently and significantly reduced levels of free endotoxin by 93-99% (p<0.0001). A significant endotoxin reduction of 39% (p<0.001) was observed after five minutes. The DACC-coated dressing incubated with clinically relevant Pseudomonas aeruginosa cells also reduced shed endotoxin by >99.95% (p<0.0001)., Conclusion: In this study, we showed that a DACC-coated wound dressing efficiently and rapidly binds both purified and shed endotoxin from Pseudomonas aeruginosa in vitro. This ability to remove both endotoxin and bacterial cells could promote the wound healing process.

Objective: This study was designed to evaluate the antibacterial activity of a wound dressing which combines polyacrylate fibres and a silver lipido-colloid matrix (UrgoClean Ag, silver polyabsorbent dressing), against biofilm of methicillin-resistant Staphylococcus aureus (MRSA)., Method: Samples of silver polyabsorbent dressing and the neutral form of this dressing (UrgoClean) were applied to biofilms of MRSA formed on a collagen I-coated surface, cultured for 24 hours. Different exposure times were tested (1, 2, 4 and 7 days) without dressing change. The biofilm reduction was quantified by using culture methods and by confocal laser scanning microscopy experiments., Results: The application of the silver polyabsorbent dressing resulted in a significant decrease of the biofilm population by a log reduction of 4.6, after 24 hours of exposure. Moreover, the antibiofilm activity was maintained for 7 days with reduction values up to 4 log (reduction of biofilm superior to 99.99%). The application of the neutral dressing also induced a significant reduction of the concentration of sessile cells after 1 day (about 0.90 log). The results obtained with this neutral form of the dressing showed that the polyacrylate fibres were able to exert a mechanical disruption of the biofilm architecture., Conclusion: These in vitro experiments demonstrated that silver polyabsorbent dressing was able to strongly reduce the biofilm of MRSA. The antibiofilm mechanism of this dressing can be explained by a dual action of the polyabsorbent fibres (based on ammonium polyacrylate polymer around an acrylic core) which induced a mechanical disruption of the biofilm matrix and/or a sequestration of sessile cells, and the diffusion of silver ions which produced bactericidal activity., Declaration of Interest: This study was supported by Laboratoires Urgo (Dijon). P. Janod is an employee of Laboratoires Urgo. The company had no influence on the experimental design and the interpretation of the results.

Objective: To date only planktonic bacteria have been shown to bind irreversibly to dialkyl carbamoyl chloride (DACC)-coated Cutimed Sorbact dressings. Therefore, this study was designed to determine whether bacterial biofilm bound to the DACC-coated dressing in vitro., Method: Samples of DACC-coated dressings and uncoated control dressings (supplied by BSN medical Ltd, Hull) were placed in contact with plastic coverslips on which biofilms of either Pseudomonas aeruginosa or methicillin-resistant Staphylococcus aureus (MRSA) had been cultivated for 24 hours. Dressing samples were examined by scanning electron microscopy to detect the presence of biofilm., Results: Pseudomonas aeruginosa biofilm bound avidly to both DACC-coated and uncoated dressing samples. MRSA bound more extensively to DACC-coated dressings than to uncoated samples., Conclusion: Biofilms of two different test bacteria bound to dressings in vitro with the DACC-coating on the dressings enhancing the binding of MRSA biofilm., Declaration of Interest: This study was supported by BSN medical Ltd (Hull). The company had no influence on the experimental design or the interpretation of the results.

Objective: To compare a superabsorbent polymer dressing (DryMax Extra; DME), an antibacterial absorbent polymer dressing (Sorbact absorption dressing; SB) and an antibacterial superabsorbent polymer dressing (Sorbion Sachet S; SSS) activity against Pseudomonas aeruginosa biofilms., Method: A 3D acellular synthetic soft tissue (ASST) allowing biofilm formation, was prepared and inoculated with Pseudomonas aeruginosa, before the application of dressings. The dressings DME, with and without a silver net, and two benchmark dressings SB and SSS were tested. After 24 hours' incubation, qualitative assessment by visual screening of the soft tissue and bacterial burden assessment in the dressings and acellular soft tissue model were performed., Results: DME combined with a silver net gave a distinct and wide colourless zone of inhibition while partial zones of inhibition were seen for DME, SSS and SB. Compared with the tissues exposed to the other dressings, those exposed to SB and the bacterial control appeared green and opaque. In descending order, the most visual growth was seen in bacterial control, followed by SB, SSS, and DME. The bacterial load was equivalent for all dressings without an antimicrobial substance in both ASST (around log 10) and dressing (around log 11). The bacterial load for DME combined with a silver net, in comparison to DME alone was significantly reduced, with log 3.6 in dressings and log 4.2 in ASST., Conclusion: The removal of bacteria by DME was equivalent to SB and SSS. Furthermore, DME limited the production of the green colour, indicative of Pyocyanin. If extrapolated to a wound, the ability of DME to absorb Pseudomonas aeruginosa and limit Pyocyanin levels in the wound might lead to reduced virulence.

Objective: To assess the effectiveness of a new, next-generation antimicrobial dressing (AQUACEL Ag+ dressing) in facilitating healing in a variety of hard-to-heal wounds that may have been compromised by infection and/or biofilm., Method: This was an international, multi-centred, real-life, non-randomised evaluation involving patients with a wide variety of slow-, non-healing or deteriorating chronic and acute wounds. There were no strict inclusion or exclusion criteria and the clinicians were asked to use their discretion in the selection of patients. The clinicians continued to use their standard protocol of care but replaced their existing primary wound-contact dressing with the next-generation antimicrobial dressing (NGAD) for up to 4 weeks. Clinicians could extend the treatment period if this was deemed clinically appropriate. Baseline assessments included wound bed characteristics, exudate level, indicators of wound biofilm, and signs and symptoms of infection. At the final assessment, the investigators reported the wound size, wound bed characteristics, and exudate level., Results: A total of 121 patients were recruited into the original evaluation, of which eight were excluded for incomplete data sets. Most wounds (73; 64%) were either venous leg ulcers (59; 52%) or diabetic foot ulcers (14; 12%). At baseline, the wounds of (26; 23%) patients were slowly improving, 65 were stagnant (58%) and 22 (19%) were deteriorating. Just under three-quarters (74%) of the wounds had suspected biofilm (criteria including failure of a wound to heal, lack of response to topical and systemic antimicrobial agents, or the presence of slimy substances on the wound surface). Following the evaluations, the average wound closure achieved for all wounds was 72.6%, 19 (17%) wounds healed, 47 (42%) achieved at least 90% wound closure, and 71 (63%) achieved at least 75% closure. The average treatment period was 4.1 weeks; 35 wounds were treated with the dressing for more than 4 weeks. Cost analysis indicated that potential antimicrobial dressing cost reductions of approximately 30% were realised using the NGAD., Conclusion: This real-life, non-randomised evaluation provides encouraging evidence that the NGAD may have a role to play in facilitating wound progression towards healing by helping to eliminate the biofilm barrier., Declaration of Interest: M. Walker, D. Metcalf, D. Parsons and P. Bowler are all employees of ConvaTec Ltd. Aysha Mendes da Mata is an independent writer and Annemarie Brown is an independent clinician, both received a fee and support from MA Healthcare to write up the evaluation using data supplied by ConvaTec.

Objective: The aim of this in vitro study was to demonstrate the binding capacity of multiple meticillin-resistant Staphylococcus aureus (MRSA) strains and compare the binding capacity to meticillin-sensitive Staphylococcus aureus., Method: The binding of Staphylococcus aureus to a surface was assessed by bioluminescent monitoring of the bacterial ATP levels. This assay can be used as an in vitro diagnostic model for bacteria binding in a critically colonised wound., Results: Eleven strains of Staphylococcus aureus were examined including MRSA, all of which efficiently and equally adhered to the dialkyl carbamoyl chloride (DACC)-coated dressing (Sorbact; Abigo Medical AB). The binding capacity was all in the same range 0.7-2.9 × 10⁶ CFU/cm². regardless of the antibiotic resistance properties of the specific strain., Conclusion: The decrease of wound bioburden of Staphylococcus aureus including MRSA is the result of the high binding capacity shown in this study and by earlier data. The findings in this study strengthen the held view that development of antibiotic resistance has minimal impact on the surface structures of the microorganisms in wounds.

Objective: Mycobacterium ulcerans is the causative agent of Buruli ulcer disease, the third most common mycobacteriosis after tuberculosis and leprosy and an emerging public health threat in sub-Saharan Africa. The bacteria produce a diffusible cytotoxin called mycolactone, which triggers the formation of necrotic lesions in cutaneous and subcutaneous tissues. The principal aim of this study was to characterise the cell surface hydrophobicity of Mycobacterium ulcerans and determine if bacteria bind to dialkyl carbamoyl chloride (DACC)-coated dressings through hydrophobic interactions in vitro. Since mycolactone displays hydrophobic groups, a secondary aim was to compare mycolactone binding to hydrophobic and standard dressings., Methods: We used hydrophobic interaction chromatography to evaluate the cell surface hydrophobicity of Mycobacterium ulcerans, compared to that of other microorganisms colonising wounds. The binding of Mycobacterium ulcerans bacteria to DACC-coated and control dressings was then assessed quantitatively by measurement of microbial adenosine triphosphate (ATP), while that of mycolactone was evaluated by fluorescence spectroscopy., Results: Compared to Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, Mycobacterium ulcerans displayed the highest cell surface hydrophobicity, irrespective of the bacterial production of mycolactone. Mycobacterium ulcerans bacteria bound to DACC-coated dressings [corrected] better than untreated controls. Mycolactone did not bind stably to hydrophobic, nor standard dressings, in the conditions tested., Conclusion: Retention of Mycobacterium ulcerans and other wound pathogens to DACC-coated dressings may help reduce the bacterial load in Buruli ulcers and thereby improve healing. Dressings efficiently capturing mycolactone may bring an additional clinical benefit, by accelerating the elimination of the toxin during the course of antibiotic treatment.