Clinical investigation of biofilm in non-healing wounds by high resolution microscopy techniques

Abstract

Objective The aim of this study was to analyse wound biofilm from a clinical perspective. Research has shown that biofilm is the preferred microbial phenotype in health and disease and is present in a majority of chronic wounds. Biofilm has been linked to chronic wound inflammation, impairment in granulation tissue and epithelial migration, yet there lacks the ability to confirm the clinical presence of biofilm. This study links the clinical setting with microscopic laboratory confirmation of the presence of biofilm in carefully selected wound debridement samples. Method Human wound debridement samples were collected from adult patients with chronic non-healing wounds who presented at the wound care centre. Sample choice was guided by an algorithm that was developed based on what is known about the characteristics of wound biofilm. The samples were then evaluated by light microscopy and scanning electron microscopy for the presence of biofilm. Details about subject history and treatment were recorded. Adherence to biofilm-based wound care (BBWC) strategies was inconsistent. Other standard antimicrobial dressings were used and no modern antiseptic wound dressings with the addition of proven antibiofilm agents were available for use. Results Of the patients recruited, 75% of the macroscopic samples contained biofilm despite the prior use of modern antiseptic wound dressings and in some cases, systemic antibiotics. Wounds found to contain biofilm were not all acutely infected but biofilm was present when infection was noted. The clinical histories associated with positive samples were consistent with ideas presented in the algorithm used to guide sample selection. Conclusion Visual cues can be used by the clinician to guide suspicion of the presence of wound biofilm. This suspicion can be further enhanced with the use of a clinical algorithm. Standard antiseptic wound dressings used in this study demonstrated limited antibiofilm efficacy. This study also highlighted a need for the clinical team to focus on expiration of dressing action and consistent practice of BBWC strategies which includes the use of proven antibiofilm agents. Declaration of interest This work was supported by the Department of Veterans Affairs Career Development Award CDA-2 1IK2BX001701 to J.A.G. Microscopical experiments were performed in part through the use of the VUMC Cell Imaging Shared Resource (supported by NIH grants CA68485, DK20593, DK58404, DK59637 and EY08126).

Consensus guidelines for the identification and treatment of biofilms in chronic nonhealing wounds

“…Although some indirect (surrogate) features on the surface of wound beds (e.g., extensive fibrinous slough) that are indicative of biofilm may be visible to the naked eye, in many cases, the actual biofilms are located in the deeper tissue layers in the wound bed (e.g., an average depth of 50–70 microns), creating issues with diagnosis. The inability to discriminate between slough and biofilm, and to reliably determine the presence of biofilm using clinical cues, may result in suboptimal care .…”

“…There is increasing evidence that biofilms are present in most, if not all, chronic nonhealing wounds . A recent meta‐analysis of in vivo studies highlights that at least 78% of chronic wounds contain a biofilm .…”

Diabetic foot infection: A critical complication

“…Wound biofilm has been linked to wound infection . This link was demonstrated in a clinical investigation involving 16 individuals with chronic wounds, predominantly of venous stasis aetiology . A recurring macroscopic material removed from the surface of the wounds was landmarked using histological techniques, and selected portions of samples were investigated using scanning electron microscopy (SEM).…”

“…. Hurlow et al used scanning electron microscopy techniques to look for the presence of biofilm within a specifically described, reoccurring, macroscopic wound bed substance. This substance, which contained biofilm, was found to reform despite the use of standard antiseptic wound dressings.…”

“…More recently, CI has been shown to have some ability to decrease microbial load in the clinical wound setting over a 7‐day period; however, this data is based on the use of a quantitative polymerase chain reaction (PCR) method directed towards bacteria regardless of phenotype. Recently, some concern has been expressed about the therapeutic longevity of any potential CI anti‐biofilm activity . In essence, it is reasonable that the inclusion of anti‐biofilm action will be necessary to achieve most cost‐effective wound care protocols of care, but reliable use of anti‐biofilm substances in the delicate environment of an exudating wound will require an improved understanding of the practical balance between anti‐biofilm substance concentration efficacy and substance toxicity, as well as attention to length of clinical efficacy.…”