Surgical Wound Infection: Symptoms, Types, Causes and Treatment

Surgical wound infections—now more commonly referred to as surgical site infections (SSIs)—are among the most frequent and challenging complications following surgical procedures. Despite advances in surgical techniques, infection control, and antibiotic prophylaxis, SSIs continue to impact patient recovery, healthcare costs, and overall outcomes. This article explores the key aspects of surgical wound infection: symptoms, types, causes, and treatment, providing an evidence-based overview for patients, healthcare professionals, and anyone interested in understanding this important postoperative issue.

Symptoms of Surgical Wound Infection

When recovering from surgery, recognizing the early signs of a wound infection is crucial for timely intervention and better outcomes. Surgical wound infections can present in various ways, from mild redness to severe systemic symptoms. Understanding these symptoms empowers patients and caregivers to seek help promptly, reducing the risk of complications.

Symptom	Description	Severity Range	Source(s)
Redness	Localized erythema around the wound	Mild to Moderate	4, 8
Swelling	Edema or puffiness at incision site	Mild to Severe	4, 8
Pain/Tenderness	Increased or persistent wound pain	Mild to Severe	4, 8
Heat	Warmth over wound area	Mild to Moderate	4, 8
Discharge	Pus or foul-smelling fluid	Moderate to Severe	1, 4, 8
Fever	Systemic temperature >38°C	Moderate to Severe	4, 8
Delayed Healing	Wound fails to close as expected	Mild to Severe	4, 8
Systemic Signs	Malaise, chills, high fever	Severe	8, 3

Table 1: Key Symptoms of Surgical Wound Infection

Early Localized Symptoms

The initial indicators of a surgical wound infection often appear at the incision site. These may include:

• Redness and Swelling: Most infected wounds develop noticeable redness and swelling around the cut. This is often accompanied by warmth, as the body’s immune system mounts a response to the invading pathogens 4.
• Pain or Tenderness: While some discomfort is normal after surgery, escalating or persistent pain should raise concern 4.

Discharge and Odor

• Pus or Foul-Smelling Fluid: The appearance of yellow, green, or cloudy discharge from the wound, especially if it has an unpleasant odor, is a hallmark of infection 1, 4.
• Delayed Wound Healing: If the surgical site fails to heal or starts to separate, infection may be impeding recovery 4.

Systemic Symptoms

• Fever and Chills: When the infection spreads beyond the local site, patients may develop fever (temperature >38°C), chills, and a general feeling of being unwell 4, 8.
• Other Systemic Effects: In severe cases, especially with deep or organ/space infections, symptoms like confusion, rapid heartbeat, or low blood pressure may develop, indicating a serious complication that requires urgent attention 3, 8.

Severity Spectrum

Symptoms can range from mild (localized redness) to severe (systemic illness). Deep or extensive infections, such as mediastinitis after cardiac surgery, often present with more pronounced systemic symptoms and require intensive management 3.

Types of Surgical Wound Infection

Not all surgical wound infections are created equal. SSIs are classified based on the depth, tissue involvement, and anatomical site affected. This classification is critical as it guides diagnosis, treatment, and prognosis.

Type	Tissue Involved	Typical Timing After Surgery	Source(s)
Superficial Incisional	Skin and subcutaneous tissues	Within 30 days	4, 8
Deep Incisional	Deep soft tissues (muscle, fascia)	Within 90 days	3, 4, 8
Organ/Space	Organs or spaces manipulated	Within 90 days	3, 4, 8
Special Cases	Cardiac (sternal/mediastinitis)	Within 1 year (with implant)	3, 4

Table 2: Types of Surgical Wound Infection

Superficial Incisional SSI

• Definition: Involves only the skin and subcutaneous tissue at the incision 4.
• Timing: Typically occurs within 30 days post-surgery unless a foreign body (like an implant) is present, in which case the risk window extends up to 1 year 4.
• Symptoms: Redness, mild swelling, pain, and sometimes minor discharge 4.

Deep Incisional SSI

• Definition: Extends into the deeper soft tissues, such as muscle and fascia 4.
• Timing: Occurs within 90 days of surgery (or up to 1 year with a foreign body) 4.
• Symptoms: Increased pain, deeper wound breakdown, abscess formation, and systemic symptoms 4, 3.

Organ/Space SSI

• Definition: Infection involving any organ or anatomical space, other than the incision, that was opened or manipulated during the procedure 4.
• Timing: Must occur within 90 days after surgery unless an implant is present 4.
• Symptoms: Often presents with systemic signs such as fever, malaise, and organ-specific symptoms (e.g., peritonitis after abdominal surgery) 4, 8.

Special Cases: Sternal Wound Infections and Mediastinitis

• Deep Sternal Wound Infection: A particularly severe form seen after cardiac surgery, subdivided into deep incisional SSI and mediastinitis (infection of the mediastinum, the central chest compartment) 3.
• Prognosis: Mediastinitis is associated with the poorest outcomes, including significantly increased mortality 3.

Clinical Relevance

Understanding the type of SSI helps tailor management strategies. For instance, superficial infections may be managed with local care and antibiotics, while deep or organ/space infections often require surgical intervention and targeted therapy 3, 4.

Causes of Surgical Wound Infection

Surgical wound infections arise from a complex interplay between patient factors, environmental exposures, surgical technique, and microbial pathogens. Identifying the underlying causes is the cornerstone of effective prevention and management.

Factor	Description	Example(s)	Source(s)
Pathogens	Bacteria (e.g., S. aureus, E. coli, MRSA)	Gram-positive/negative	1, 5, 6
Patient Risk	Age, comorbidities, immune status	Diabetes, obesity, elderly	6, 8
Surgery Risk	Operation type, wound class, duration, implant	GI, orthopedic, trauma	8, 6, 3
Environmental	Staff carriers, aseptic breaches	S. pyogenes outbreaks	7, 9
Microbial Origin	Endogenous or exogenous contamination	Patient flora, hospital	6, 9

Table 3: Causes of Surgical Wound Infection

Microbial Pathogens

• Common Bacteria: The most frequently isolated organisms in SSIs are Staphylococcus aureus (including MRSA), Escherichia coli, Pseudomonas aeruginosa, Klebsiella spp., and Enterococcus spp. 1, 5, 6.
• Antibiotic Resistance: The rise of multidrug-resistant organisms, especially MRSA, poses a major challenge to effective treatment 1, 5.
• Polymicrobial Infections: Many SSIs, particularly in abdominal or trauma surgeries, involve multiple bacterial species 6.

Patient-Related Risk Factors

Certain patient characteristics increase susceptibility to wound infection:

• Advanced Age: Older patients, especially those over 65 or 75, are at higher risk 6, 8.
• Comorbidities: Diabetes, chronic diseases, obesity, and immune compromise all elevate infection risk 6, 8.
• Pre-existing Infections: The presence of other infections or colonization with pathogens (e.g., nasal carriage of S. aureus) heightens SSI risk 6.

Surgery-Related Risk Factors

• Type of Surgery and Wound Classification: Orthopedic and abdominal surgeries, as well as contaminated or dirty wounds, carry a higher infection risk 8, 6.
• Operation Duration: Longer surgeries are associated with increased risk 8, 6.
• Hospitalization: Prolonged preoperative and postoperative hospital stays increase SSI rates, likely due to increased exposure to hospital microbes 8.

Environmental and Procedural Factors

• Aseptic Technique: Inadequate sterile technique or breaches in asepsis (e.g., staff acting as carriers of S. pyogenes) can cause outbreaks 7, 9.
• Healthcare Staff: Surgical team members have occasionally been traced as the source of outbreaks, especially with highly transmissible organisms 7.

Routes of Infection

• Exogenous: Infection introduced from the environment, surgical instruments, or staff 7, 9.
• Endogenous: Infection arising from the patient’s own flora, either at the skin or from distant sites (e.g., gums or intestines—so-called "Trojan Horse" mechanism) 6, 9.

Emerging Insights

Recent research suggests that not all SSIs are due to intraoperative contamination. Some may result from bacteria migrating from remote body sites after surgery, emphasizing the need for broader preventive strategies 9.

Treatment of Surgical Wound Infection

Timely and effective treatment of SSIs is essential to prevent complications and promote healing. Management strategies vary depending on the type and severity of infection, the causative organism, and patient factors.

Treatment	Purpose	Notes/Effectiveness	Source(s)
Antibiotics	Eradicate infection	Guided by culture/sensitivity	1, 5, 6
Topical Agents	Reduce local bacterial load	Useful for superficial wounds	13
NPWT	Promotes healing, reduces SSI	Reduces infection, aids closure	10, 11, 12, 14
Surgery	Drain abscess, remove tissue	Needed for deep/organ-space infection	3, 4
Infection Control	Prevent recurrence	Includes surveillance, hygiene	2, 5, 8

Table 4: Treatment Approaches for Surgical Wound Infection

Antibiotic Therapy

• Empirical Therapy: Initial antibiotics are chosen based on the most likely pathogens and local resistance patterns 1, 5, 6.
  • Staphylococcus aureus is the most common organism; MRSA should be considered, especially in high-risk settings 1, 5.
  • Amikacin, linezolid, and tigecycline are effective against many resistant strains, while vancomycin is reserved for MRSA (no vancomycin-resistant strains detected in some studies) 1, 5.
• Culture-Guided Therapy: Treatment is refined once microbiology results are available, ensuring targeted and effective eradication 1, 5, 6.
• Multidrug Resistance: The rise in resistant organisms underscores the need for judicious use of antibiotics and ongoing surveillance 1, 5.

Topical Antibiotics

• Effectiveness: Topical antibiotics, when applied to wounds healing by primary intention, probably reduce the risk of SSI compared to no antibiotic or antiseptic 13.
• Risks: Potential for allergic contact dermatitis exists, but is rare; impact on broader antibiotic resistance remains unclear 13.

Negative Pressure Wound Therapy (NPWT)

• Mechanism: NPWT (vacuum-assisted closure) involves applying controlled suction to the wound, removing exudate and promoting tissue perfusion 10, 11, 12, 14.
• Efficacy: Multiple randomized trials and meta-analyses show that NPWT can reduce the risk of SSI by 40–50% compared to conventional dressings, across various surgical specialties 10, 11, 12, 14.
• Other Benefits: NPWT also reduces wound dehiscence and seroma incidence and may speed up healing 12, 14.
• Limitations: Not recommended for all wounds; possible increased risk of device-related adverse events in some studies 14.

Surgical Intervention

• Indications: Deep incisional and organ/space infections, especially those with abscess formation or necrotic tissue, often require surgical drainage, debridement, or even removal of implants 3, 4.
• Complex Cases: Mediastinitis after cardiac surgery requires aggressive multidisciplinary management 3.

Infection Control and Prevention

• Hospital Protocols: Implementation of infection control measures (e.g., hand hygiene, surveillance, antibiotic stewardship) significantly reduces SSI rates 2, 5, 8.
• Accreditation and Continuous Improvement: Hospitals benefit from ongoing self-assessment and adherence to best practices to lower infection rates 2.

Conclusion

Surgical wound infections remain a significant challenge in postoperative care, but increased awareness, early recognition, and evidence-based management can greatly improve outcomes. Here’s a summary of the key points:

• Symptoms: Watch for redness, swelling, pain, discharge, fever, and delayed healing after surgery.
• Types: SSI classification (superficial, deep, organ/space) determines severity and treatment approach.
• Causes: Infections arise from patient risk factors, surgery-related risks, environmental exposures, and a range of bacterial pathogens—including resistant strains.
• Treatment: Combines antibiotics (systemic and topical), advanced wound therapies like NPWT, surgical intervention for severe cases, and stringent infection control measures.

By understanding the symptoms, types, causes, and modern treatment strategies for surgical wound infections, both patients and healthcare teams can take proactive steps to ensure optimal recovery and minimize complications.