Healthy vs. Infected Wounds: A Clinician’s Guide

As a clinician, distinguishing between healthy and infected wounds is critical for ensuring the best patient outcomes and minimizing complications.

For example, using antibiotics for  a healthy wound is unnecessary and can contribute to antibiotic resistance. Alternatively, not treating infected wounds with antibiotics can lead to complications such as a chronic wound that extends the treatment timeline, or even cellulitis or sepsis.

To broaden your repository of wound knowledge, we’ll address the differences in healthy vs. infected wounds, treatment distinctions, and other key factors to consider.

Healthy Vs. Infected Wounds: What Every Clinician Should Know

Put simply, a healthy wound is one that heals as clinically expected, without any signs of infection. You’ll typically see the wound getting smaller, healthy red tissue forming, and new skin growing over it. There should be little to no pus.

Conversely, an infected wound is one that shows signs that harmful bacteria or other pathogens are replicating.  These signs can include increased pain, redness, swelling, pus-like drainage, delayed  healing, fragile and discolored tissue, a foul odor, or generalized signs of illness.

Differing Characteristics

What are the different characteristics of healthy vs. infected wounds? Here’s a breakdown of the general characteristics of these types of wounds.

Healthy Wounds

• Appearance: Progressive reduction in wound size. Granulation tissue is robust, with a “beefy red” or pink appearance, and moist. New skin growth is visible as a thin, pink, or white margin advancing inward. Minimal to no drainage; however, if present, it’s typically clear or yellowish.
• Sensation: Pain decreases over time with minimal tenderness.
• Temperature/inflammation: Redness and swelling decrease as the wound heals. Warmth is generally consistent with surrounding tissue or slightly elevated during the initial inflammatory phase.
• Healing progression: Demonstrates consistent, measurable progress towards closure. Wound edges are well-approximated or contracting.

Infected Wounds

• Appearance: Delayed healing or wound breakdown. Granulation tissue may be friable (easily crumbled), discolored (dark red, grey, or black), or absent. Purulent drainage is present, which can be yellow or green and/or have a foul odor. May have increased induration (hardening of tissue).
• Sensation: Increased pain and tenderness, often disproportionate to the wound size.
• Temperature/inflammation: Increased redness, swelling, and warmth extending beyond the immediate wound margins. May present with localized or spreading cellulitis.
• Healing progression: Lack of progress towards closure or increased wound size. May have wound dehiscence (separation of wound edges). May be accompanied by fever, chills, malaise, or other signs of systemic infection.

In Consideration of Inflammation A critical clinical skill to maintain when working in wound treatment is distinguishing between the expected inflammatory response of wound healing and signs of true infection. While both present redness, swelling, and warmth—as noted above—the context and progression differ significantly and needs further discussion. Normal inflammation, a necessary part of healing, peaks within the first few days and gradually subsides. Redness is localized, warmth is mild, and swelling decreases progressively. Pain is proportional to the wound severity and diminishes with time. Meanwhile, infection intensifies these symptoms. Redness and swelling (edema) spread beyond the wound margins, warmth is excessive, and pain worsens or remains unrelenting. The hallmarks of infection present themselves: purulent drainage, an unpleasant odor, and friable, discolored granulation tissue. Systemic signs like fever, chills, and swollen lymph nodes further distinguish infection from the normal inflammatory response. It’s essential to meticulously evaluate the temporal pattern and characteristics of these signs to differentiate normal healing from infection.

Treatment Distinctions

Treating healthy vs. infected wounds requires distinct approaches. The primary goal when treating a healthy wound is to create an optimal environment for natural healing; but infected wounds require a more aggressive approach to eliminate the infection and promote healing.

Here are some guidelines for treating each wound type based on these goals.

Healthy Wounds

• Gentle cleaning: Rinse the wound with clean, running water or a sterile saline solution to remove debris. Though it’s long been a practice to use harsh antiseptics like hydrogen peroxide or rubbing alcohol, many health experts have been recently advising against their use as these products can damage healthy tissue and delay healing.
• Appropriate dressings: Select dressings that maintain a moist wound environment, which promote cell migration and epithelialization. This might include hydrocolloids, foams, or alginates, depending on the amount of drainage.
• Protection: Cover the wound with a sterile bandage to prevent contamination. In some cases, especially with minor abrasions, allowing the wound to air-dry may be best.
• Supportive care: Ensure adequate nutrition to support the healing process. Managing any underlying conditions that could impede healing, such as diabetes or vascular disease. Offloading pressure from the wound when applicable.

Infected Wounds

• Antimicrobial therapy: Use topical antibiotics for localized infections or systemic antibiotics (oral or intravenous) for more severe or spreading infections. Wound cultures are crucial in identifying the causative organisms and guiding antibiotic selection. Consider a swab culture, which “has sufficient correlation with tissue biopsy to identify causative organisms in an infected wound,” studies have found.
• Debridement: Remove necrotic tissue, debris, and biofilm, which can harbor bacteria and impede healing. This may be done surgically, enzymatically, or mechanically.
• Wound bed preparation: Create a clean, viable wound bed to promote granulation tissue formation. This may involve using specialized dressings or negative pressure wound therapy.
• Management of systemic infection: Address any systemic signs of infection, such as fever or sepsis, with appropriate medical interventions. In some cases, surgical intervention may be necessary to remove infected tissue, drain abscesses, or repair damaged structures.
• Close monitoring: Perform frequent monitoring of the wound and the patient’s overall condition to ensure that the infection is resolving and healing is progressing.

The Biology of Wound Healing

The biology of wound healing is a complex and finely orchestrated process that aims to restore tissue integrity after injury. It involves a cascade of cellular and molecular events that can be broadly categorized into four overlapping phases:

• Hemostasis
• Inflammation
• Proliferation
• Remodeling

Hemostasis (immediate) is the body’s initial response to injury, where the goal is to stop bleeding. Platelets aggregate at the injury site, forming a clot that acts as a temporary barrier to prevent further blood loss. Eventually, growth factors and fibroblasts are released, and collagen is produced, initiating the subsequent phases of wound healing.

Inflammation (1-6 days) is characterized by the influx of immune cells to the wound site. Neutrophils are the first to arrive, clearing debris and bacteria. Macrophages then take over, further removing debris and releasing growth factors that stimulate fibroblast and endothelial cell activity. As its name suggests, this phase is marked by expected redness, swelling, warmth, and pain.

Proliferation (6-21 days) focuses on rebuilding the damaged tissue. Fibroblasts migrate to the wound site and synthesize collagen, creating a new connective tissue matrix. New blood vessels form to supply the healing tissue with oxygen and nutrients. Epithelial cells migrate from the wound edges to cover the wound surface, creating a new layer of skin. Myofibroblasts (specialized fibroblasts) contract the wound edges, reducing the wound size.

Remodeling (21+ days), or maturation, is the final phase of wound healing. It’s characterized by the remodeling of the collagen matrix to increase  tensile strength of the healed tissue. Collagen is reorganized and cross-linked, increasing the strength and flexibility of the scar. This phase can last for months or even years, and the scar can continue to change in appearance and strength.

Did you know that repaired tissue will only achieve roughly 80% of the original skin’s tensile strength?

How Infection Impairs Wound Healing

Wound healing isn’t always a straightforward process. Oftentimes, it can become prolonged due to issues such as necrosis, poor nutrition, insufficient blood supply, and other underlying conditions. But one common reason for delayed healing is infection.

Infection has multiple impacts on wound healing, including:

• Increased risk of chronic wounds.
• Delayed wound closure.  
• Increased pain and discomfort.  
• Increased risk of systemic infection.
• Increased healthcare costs.
• Increased scarring.  
• Reduced patient quality of life.

“Infection at the site of the wound [results] in excessive recruitment of inflammatory cells,” says a study on granulation tissue’s role in wound healing and repair. These infections “result in increased release of reactive oxygen species that are damaging to the tissue and can also result in the formation of biofilms, which contribute to poor wound healing and are caused by bacterial toxins.”

Here’s a walkthrough of how this disruption occurs in the latter three phases of wound healing.

Prolonged and Dysregulated Inflammation

Normally, inflammation is a controlled, transient phase. However, in infected wounds, the presence of bacteria and their byproducts triggers a persistent and excessive inflammatory response that impairs healing.

This response leads to:

• Increased release of pro-inflammatory cytokines that can damage healthy tissue.  
• Excessive redness and swelling, hindering nutrient and oxygen delivery.
• Impaired migration of fibroblasts and other cells essential for tissue repair.

The longer the inflammatory period, the longer the transition delay to the proliferation phase.

Disrupted Proliferation

Infection impairs the formation of granulation tissue since and inflammatory mediators can damage fibroblasts, reducing collagen synthesis and the formation of healthy granulation tissue. The granulation tissue that does form may be friable, discolored, or insufficient.

Bacterial toxins and inflammatory cytokines can inhibit the formation of new blood vessels, compromising oxygen and nutrient supply and delivery to the healing tissue. Coupled with excessive drainage, bacterial presence can hinder the migration of epithelial cells across the wound surface.

In addition, infection increases matrix metalloproteinases (MMPs), enzymes that break down the extracellular matrix. While some MMP activity is necessary for remodeling, bacterial infection increases MMP production, and these MMPs can degrade newly formed collagen—along with other necessary extracellular matrix components—thus impairing healing.

In some cases, an infection may lead to the formation of biofilms, which are structured bacteria communities that adhere to the wound surface. Biofilms are highly resistant to antibiotics and host immune defenses, creating a chronic source of infection and hindering healing.

Impaired Remodeling

Even if the wound eventually closes, infection can disrupt the remodeling phase, leading to:

• Weakened scar tissue due to inadequate collagen organization.
• Increased risk of scar contracture or dehiscence (wound reopening).
• Excessive scar tissue due to chronic inflammation.

Understanding Healthy Vs. Infected Wounds Is Key

Healthy wounds progress through predictable healing phases and are characterized by smaller wound size, healthy red tissue, and minimal drainage. In contrast, infected wounds exhibit delayed healing, purulent drainage, and a systemic inflammatory response.

Infection disrupts the intricate biological processes of wound healing by prolonging inflammation, impairing proliferation, and hindering remodeling. Understanding these disruptions is crucial for accurate diagnosis and a specific, tailored treatment. As a clinician, it’s key to prioritize prompt intervention, including appropriate antimicrobial therapy and debridement, to prevent complications and optimize patient outcomes.

Recognizing the impact of infection on wound healing promotes effective wound care and antibiotic selection, ultimately improving patient recovery and quality of life.