Human skin biofilm model: translational impact on swabbing and debridement

Abstract

Objective: Wound biofilms are one of the greatest challenges in the therapy of hard-to-heal (chronic) wounds, as potent antimicrobial substances fail to eradicate bacteria within short incubation periods. Preclinical investigations using novel model systems that closely mimic the human wound environment and wound biofilm are required to identify new and effective therapeutic options. This study aims to identify bacterial colonisation patterns that are relevant for diagnosis and therapy. Method: In this study, a recently established human plasma biofilm model (hpBIOM) was incorporated into a wound within human dermal resectates after abdominoplasty. The interaction of the biofilm-forming bacteria meticillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa with the skin cells was investigated. Possible effects on wound healing processes in correlation with the persistence of the biofilm in the wound environment were analysed in patients with leg ulcers of different aetiologies and biofilm burden. Results: Using haematoxylin and eosin staining, species-dependent infiltration modes of the bacteria into the wound tissue were determined for the pathogens MRSA and Pseudomonas aeruginosa. The spreading behaviour correlated with clinical observations of the spatial distributions of the bacteria. In particular, the clinically prominent Pseudomonas aeruginosa-specific distension of the wound margin was identified as epidermolysis due to persistent infiltration. Conclusion: The hpBIOM applied in this study represents a potential tool for preclinical analyses dealing with approval processes for new antimicrobial applications. In terms of clinical practice, a microbiological swabbing technique including the wound margin should be routinely applied to prevent wound exacerbation.

Quantitative Insights and Visualization of Antimicrobial Tolerance in Mixed-Species Biofilms

“…Using UV-near light (405 nm, MolecuLight ® , MolecuLight Corp.; Toronto, ON, Canada) to detect wound areas with a high bacterial burden (10 4 cfu/g) also reflects this phenomenon: when P. aeruginosa-specific metabolic products (e.g., pyoverdins) are detected by means of cyan blue fluorescence, a wide distribution and a bright glow are very often observed due to a high level of colonization and infiltration of the wound. The rather unspecific red fluorescence of the metabolic products (e.g., porphyrins) of, e.g., Gram-positive S. aureus or Enterobacteria, is considerably inferior here [14]. However, if P. aeruginosa is not detectable among the wound pathogens, the red fluorescence is much more pronounced and widespread.…”

“…For example, interleukin-1β and matrix metalloproteases (MMP) 2 [25,26] or lactate [27] increase with inflammation and infections. The wound environment, represented in lh-BIOM by human blood plasma, immune cells, bacteria themselves and their products, also influences the composition of the EPS of the biofilm [14]. This plays an essential role in the biofilm's typical tolerance to antimicrobials [22].…”

“…It is a mechanical, chemical and physical barrier. The EPS with its embedded and surrounding bacteria also interacts with the human cells of the wound bed [14], which in turn causes changes in the environment. Biofilm models free of human components do not allow such deep insights into host-bacteria interactions [28,29].…”

Characterization of the Human Plasma Biofilm Model (hpBIOM) to Identify Potential Therapeutic Targets for Wound Management of Chronic Infections

“…A major challenge in the current guideline development is the transfer of data based on in vitro biofilm models developed on solid surfaces (glass slides or cell culture wells) to the clinical wound situation. In contrast, the hpBIOM and comparable models present the adhesion possibilities and the milieu of acute and chronic wounds, which make it more suitable for translational wound research [ 44 ].…”