Antimicrobial Hypochlorous Wound Irrigation Solutions Demonstrate Lower Anti-biofilm Efficacy Against Bacterial Biofilm in a Complex in-vitro Human Plasma Biofilm Model (hpBIOM) Than Common Wound Antimicrobials.

Julian-Dario Rembe,Lioba Huelsboemer,Ewa K Stuermer,Isabell Plattfaut,Manuela Besser

doi:10.3389/fmicb.2020.564513

Abstract

Biofilms pose a relevant factor for wound healing impairment in chronic wounds. With 78% of all chronic wounds being affected by biofilms, research in this area is of high priority, especially since data for evidence-based selection of appropriate antimicrobials and antiseptics is scarce. Therefore, the objective of this study was to evaluate the anti-biofilm efficacy of commercially available hypochlorous wound irrigation solutions compared to established antimicrobials. Using an innovative complex in-vitro human plasma biofilm model (hpBIOM), quantitative reduction of Pseudomonas aeruginosa, Staphylococcus aureus, and Methicillin-resistant S. aureus (MRSA) biofilms by three hypochlorous irrigation solutions [two <0.08% and one 0.2% sodium hypochlorite (NaClO)] was compared to a 0.04% polyhexanide (PHMB) irrigation solution and 0.1% octenidine-dihydrochloride/phenoxyethanol (OCT/PE). Efficacy was compared to a non-challenged planktonic approach, as well as with increased substance volume over a prolonged exposure (up to 72 h). Qualitative visualization of biofilms was performed by scanning electron microscopy (SEM). Both reference agents (OCT/PE and PHMB) induced significant biofilm reductions within 72 h, whereby high volume OCT/PE even managed complete eradication of P. aeruginosa and MRSA biofilms after 72 h. The tested hypochlorous wound irrigation solutions achieved no relevant penetration and eradication of biofilms despite increased volume and exposure. Only 0.2% NaClO managed a low reduction under prolonged exposure. The results demonstrate that low-dosed hypochlorous wound irrigation solutions are significantly less effective than PHMB-based irrigation solution and OCT/PE, thus unsuitable for biofilm eradication on their own. The used complex hpBIOM thereby mimics the highly challenging clinical wound micro-environment, providing a more profound base for future clinical translation.

Highlights

In wound management, controlling microbial bioburden is a key factor of prophylactic and therapeutic regimes
Due to the recent renaissance of hypochlorous acid based antimicrobial wound irrigation solutions (Severing et al, 2019) with contrasting evidence regarding anti-biofilm efficacy, this study focused on the evaluation of these agents compared to established antimicrobial and antiseptic agents
Prolonged exposure times of up to 72 h for 0.3 ml OCT/PE and PHMB increased bacterial reduction of all three pathogens with a continuous decrease in bacterial counts yielding highest reductions after 72 h of exposure compared to the untreated control (Figures 2A–C)

Summary

Introduction

In wound management, controlling microbial bioburden is a key factor of prophylactic and therapeutic regimes. While wound contamination and colonization can mostly be handled with vigilance and mechanical cleansing, local infection with the potential threat of systemic spread requires antimicrobial intervention (IWII, 2016). Possible interventions range from preserved antimicrobialscontaining wound irrigation solutions to antiseptics, debridement and systemic antibiotics in case of systemic spread. Biofilm formation thereby represents a difficult to diagnose and manage complication in wound therapy. Biofilms are structured communities of microorganisms attached to a surface (e.g., wound bed) encased within an extracellular matrix (ECM) referred to as the extracellular polymeric substance (EPS; Percival et al, 2015). Wound antimicrobials and antiseptics need to be thoroughly investigated regarding their anti-biofilm efficacy (Schultz et al, 2017)

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Conclusion