Understanding Wound Healing: How to Recognise and Treat Biofilm in Pressure Injury

Biofilms contribute to 65–80% of infections in humans and are detected in approximately 80% of chronic wounds, although the true prevalence may be closer to 100%. Cutaneous wound healing is the process by which the skin repairs itself after injury.

Biofilms obstruct the host’s immune response, weaken the skin barrier, and alter the extracellular matrix (ECM), a structure essential for rebuilding healthy tissue, supporting wound tissue, and maintaining the body’s natural mechanisms for tissue repair and integrity.

As a result, they delay wound healing and increase wound chronicity. Enhancing clinicians’ understanding of biofilms and best-practice treatment strategies is essential to improving wound healing outcomes.

Healing Phases

The process of wound healing unfolds in a series of well-orchestrated healing phases, each marked by specific cellular and molecular activities. The first stage, known as the inflammatory phase, begins immediately after injury.

During this phase, white blood cells such as neutrophils and macrophages rush to the wound site to clear away debris, dead tissue, and bacteria, helping to prevent infection and initiate the healing response.

Next, the proliferative phase takes over, characterised by the formation of granulation tissue, the growth of new blood vessels (angiogenesis), and the production of connective tissue. This phase is vital for rebuilding the wound bed and supporting new tissue growth.

Finally, the remodelling phase refines and strengthens the newly formed tissue, reorganising collagen fibers and restoring the wound’s tensile strength. Each of these healing phases is essential for effective wound repair, and any disruption can lead to delayed healing or chronic wounds.

Recognising the signs of each phase helps guide treatment and supports the overall healing process.

What is a Wound Biofilm and How Does it Affect Healing?

Why Biofilms are Resistant to Antibiotics

Bacteria within biofilms are 1,000 to 1,500 times more resistant to antibiotics than their free-floating counterparts. Their slower growth makes them less susceptible to antibiotics, which often target metabolically active bacteria. Additionally, bacteria within biofilms can transfer resistance genes to one another, increasing their adaptability and persistence.

Common Bacteria Found in Wound Biofilms

Biofilms commonly contain a mixture of bacterial species, including:

• Enterococcus faecium
• Staphylococcus aureus
• Klebsiella pneumoniae
• Klebsiella pneumoniae
• Acinetobacter baumannii
• Pseudomonas aeruginosa
• Enterobacter spp.

This microbial diversity, along with interspecies gene exchange, allows even non-virulent bacteria to become more aggressive pathogens, complicating wound healing.

Identifying Biofilm in Chronic Wounds

Why Biofilms Are Hard to Detect

Biofilm is not visible to the naked eye. The gold standard for detection is scanning electron microscopy. Some handheld fluorescence imaging devices can detect both planktonic and biofilm-associated bacteria, but these are not widely available in clinical settings.

Signs and Symptoms of Biofilm in Wounds

Clinicians are advised to assume biofilm is present in all chronic wounds, particularly when these signs are observed:

• Stalled wound healing
• Persistent local infection despite antimicrobial treatment
• Presence of slough or necrotic tissue
• Increased wound exudate
• Hypergranulation (overgrowth of tissue) or friable granulation tissue (easily damaged healing tissue)
• Malodour

Biofilm is a particular concern in pressure injuries and other chronic skin wounds, where persistent infection and delayed healing are common.

Bacterial cultures may help guide antimicrobial use, but as different areas of a wound may harbor different species, sampling may not reflect the full microbial load.

How Biofilms Disrupt the Wound Healing Process

Prolonged Inflammation and Tissue Damage

Biofilms are widely regarded as the most significant cause of delayed wound healing. Wounds affected by biofilm often heal slowly due to ongoing inflammation.

They prolong the inflammatory phase of healing by releasing toxins and enzymes that damage tissue, trigger persistent inflammation, and suppress the immune system’s ability to fight infection. Slow healing wounds are frequently associated with biofilm presence and require targeted intervention.

Effects on Skin Barrier and Extracellular Matrix (ECM)

Residual subdermal biofilm can impair trans-epidermal water loss (TEWL)—the skin’s natural moisture barrier—and alter the ECM. It reduces collagen production and increases the activity of collagen-degrading enzymes.

This results in weaker repaired tissue and a higher likelihood of wound recurrence. Even after a wound is healed, the tissue may not regain its original strength and can be more susceptible to hypertrophic scars, which are characterised by excessive connective tissue deposition and altered tissue structure.

Growth Factors and Wound Healing

Growth factors are key regulators in the wound healing process, orchestrating the activities of various cells involved in tissue repair. These naturally occurring proteins, such as platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and transforming growth factor-beta (TGF-β), stimulate cell proliferation, migration, and differentiation at the wound site.

By promoting the formation of new blood vessels, encouraging the growth of granulation tissue, and supporting the production of extracellular matrix, growth factors help wounds heal more efficiently. In clinical practice, growth factors may be applied topically or delivered systemically to enhance healing, especially in wounds that heal slowly or are at risk of becoming chronic.

While research into the therapeutic use of growth factors is ongoing, their role in the healing process highlights the importance of a well-coordinated cellular response for successful wound repair.

Wound Healing: Best Practices for Managing Biofilm

Understanding the four stages of wound healing – haemostasis, inflammation, proliferation, and remodelling, is essential for effective wound management and biofilm control.

Although many biofilm-targeting therapies show promise in laboratory studies, few have proven consistently effective in clinical settings. The current gold standard in managing biofilm and promoting wound healing involves regular debridement and targeted antibacterial treatment.

Research into emerging therapies continues, but the foundation of effective biofilm management remains rooted in mechanical intervention and topical support.

By effectively managing biofilm, clinicians can help ensure the wound heals efficiently and progresses through each stage of healing.

Wound Healing Strategies: How to Disrupt Biofilm

Wound Cleansing Protocols

Cleansing is a critical step in wound healing. Use a wound cleanser that contains both antiseptic and surfactant agents:

• Topical antiseptics can penetrate and disrupt biofilm while reducing the need for systemic antibiotics.
• Surfactants lower surface tension, prevent microbial adhesion, and help lift away debris and necrotic tissue. They also support autolytic debridement and reduce inflammation.
• Normal saline is a gentle, sterile solution commonly used for wound irrigation and for activating certain antimicrobial dressings, such as silver dressings, to maintain their effectiveness.

Cleanse the wound bed, periwound area, and surrounding skin thoroughly. Repeat cleansing after debridement to remove any remaining debris.

Debridement Techniques

Regular debridement eliminates dead tissue and biofilm, helping to reset the wound healing environment.

• Mechanical debridement: Using gauze or specially designed pads.
• Surgical or sharp debridement: Performed by a doctor in an aseptic setting for wounds with extensive necrosis. Wounds closed by primary intention, such as surgical incisions, typically heal faster with minimal scarring.
• Conservative sharp wound debridement (CSWD): Conducted by trained nurses in clinical settings; removes loose tissue without cutting into healthy skin, minimising pain and bleeding.
• Autolytic debridement: Recommended when mechanical or sharp debridement is contraindicated. It relies on the body’s own enzymes to break down necrotic tissue and requires a moist wound environment. Wounds healing by secondary intention require tissue regeneration from the base up and may result in more prominent scarring.

Biofilm can reform within 24 hours, so cleansing and debridement should occur at every dressing change.

Using Topical Antimicrobials Effectively

Topical antimicrobials work best when applied immediately after debridement and cleansing:

• Silver nanoparticle dressings: Inhibit both planktonic bacteria and biofilm at all stages.
• Cadexomer iodine: Penetrates biofilm and offers sustained antimicrobial activity.
• Manuka honey: Has antibacterial properties and may reduce resistance in strains like MRSA. It is most effective in biofilm prevention.

Advanced Therapies for Wound Healing

In addition to traditional wound care, several advanced therapies have been developed to promote optimal wound healing, particularly in complex or chronic wounds. Negative pressure wound therapy (NPWT) uses a vacuum dressing to increase blood flow, remove excess exudate, and stimulate the formation of granulation tissue, creating an environment that supports rapid tissue growth.

Bioengineered skin substitutes provide a scaffold for new skin cells to grow, helping to close wounds that might otherwise heal slowly or incompletely. Hyperbaric oxygen therapy delivers high concentrations of oxygen to the wound site, enhancing blood supply and supporting the healing of tissues that are deprived of oxygen.

These advanced therapies can be used alone or alongside standard wound care practices to improve healing outcomes, especially in wounds with compromised blood flow or those at risk of infection.

Improving Wound Healing by Targeting Biofilm

Biofilms present a major obstacle to effective wound healing, increasing the risk of chronicity, infection, and recurrence. Most wounds, when managed appropriately, heal within a few months, but factors such as blood supply and wound size can influence the healing timeline.

Clinicians should presume biofilm presence in all chronic wounds. Successful wound healing relies on biofilm disruption through cleansing, debridement, and targeted topical antimicrobials. Adequate vitamin C intake is crucial for collagen synthesis, as it supports the hydroxylation of proline and lysine residues, stabilising the collagen structure and promoting effective tissue repair.

Continued awareness and education on biofilm management are essential to improving healing outcomes and reducing wound complications.