What is wound biofilm? And how to recognise it
Wound biofilm is a complex structure formed by communities of bacteria and other microorganisms. Its presence in a wound is problematic as, unlike free-floating bacteria, biofilm-encased bacteria can be more resistant to the body's immune response and traditional antibiotic treatments. Biofilms are present in most chronic wounds and are likely to be located both on the surface and in deeper wound layers¹.
The presence of biofilm in hard-to-heal wounds and its significant contribution to delayed healing is well documented². Knowing how to recognise wound biofilm means understanding the characteristics and clinical signs that can suggest its presence through a combination of clinical assessment, patient history and laboratory testing.
Change in Wound Appearance
Biofilm-associated wounds may have a characteristic appearance, such as a slimy or discoloured film on the wound bed. The wound may appear to have stalled in the inflammatory phase of healing.
Clinical signs of wound biofilm in a hard-to-heal wound
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Delayed healing
If a wound shows prolonged healing despite appropriate wound care, it may raise suspicion of biofilm presence. In this situation, the wound may remain open and fail to progress through the typical stages of healing. All wounds, particularly hard-to-heal ones, will benefit from wound hygiene³. -
Recurrent infections
Persistent or recurrent infections in the same wound site despite appropriate wound care could indicate the presence of biofilm, as biofilms can protect bacteria from the immune system and antibiotics. You may observe a cycle of healing and deterioration, with increased redness, warmth, and swelling around the wound, as well as pus drainage. Non-healing wounds are devastating for patients, potentially causing long-term morbidity and an impaired quality of life. They also incur a huge health economic burden for health-care services⁴.
Biofilm-Associated Symptoms
Patients with biofilm-associated wounds may report symptoms such as increased pain, foul odour or changes in wound appearance.
Exudate Characteristics
Wound biofilm can contribute to an increased level of wound exudate. Wound exudate is produced as a natural and essential part of the healing process. Although too much or insufficient exudate delays wound healing⁵.
Clinical Assessment
You can assess a chronic wound for the presence of wound biofilm by examining the wound bed and surrounding tissue and checking for signs of infection. Taking a sample with a sterile cotton swab will allow further analysis.
Laboratory Testing
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Wound Cultures
Collecting wound cultures can help identify the specific bacteria present in the wound and guide antibiotic therapy. However, traditional culture methods may not always detect biofilm-forming bacteria effectively. -
Biopsy and Histopathology
A biopsy of the wound tissue, followed by histopathological examination, may reveal the presence of biofilm. As this is a more invasive method it is not commonly used unless other diagnostic methods are inconclusive. -
Advanced Imaging Techniques
Advanced imaging techniques, such as confocal laser scanning microscopy or scanning electron microscopy, can be used to visualise biofilm structures. However, these more specialised methods may not be readily available in all clinical settings.
Diagnostic Tools
Some diagnostic tools are being developed to detect biofilm-related components, such as specific biomarkers or genetic material. These tools are still in the research phase and may not be widely available for routine clinical use.
Recognising wound biofilm is challenging, and a combination of clinical judgment and diagnostic tools are needed to make informed decisions about treatment. If there is suspicion of biofilm involvement in a hard-to-heal wound, consulting with a wound care specialist is an obvious course of action for a more thorough assessment and appropriate management.
References
1. Schultz 2017 Consensus guidelines for the identification and treatment of biofilms in chronic nonhealing wounds
2 & 3. Murphy 2020 Journal of Wound Care International Consensus- Defying hard-to-heal wounds with an early antibiofilm intervention strategy: wound hygiene
4. Murphy 2022 Implementation of Wound Hygiene in clinical practice: early use of antibiofilm strategy promotes positive patient outcomes
5. WUWHS 2019 Consensus Document - Wound Exudate: effective assessment and management
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