Surgical Infection
Definition
A surgical infection is an infection that occurs in the surgical wound or operative field, most commonly within 30 days post-surgery, or up to 90 days if a prosthetic implant is used.
It results from the invasion and multiplication of pathogenic microorganisms, which breach normal protective barriers and evade the immune system, leading to inflammation and potentially life-threatening complications.
Why It Matters
- Can cause:
- Life- threatening complications
- Prolonged hospitalization
- Delayed wound healing
- Cosmetic and functional problems
- Surgical site infections (SSIs) are among the most common hospital-acquired infections.
Most Common Pathogens
From your notes and the PPT:
- Gram-positive bacteria:
- Staphylococcus aureus (most common overall)
- Streptococcus pyogenes
- Neisseria meningitidis, N. gonorrhoeae
- Gram-negative bacteria:
- Escherichia coli
- Proteus spp.
- Pseudomonas aeruginosa
- Anaerobes:
- Clostridium species (esp. gas gangrene, tetanus)
Classification of Surgical Infections
- By microbial cause:
- Monomicrobial – one microorganism (e.g., S. aureus)
- Polymicrobial – multiple organisms from the same group
- Mixed infection – organisms from different groups (e.g., Gram-positive + anaerobes)
- Superinfection – infection superimposed on pre- existing infection
- By anatomical location (CDC classification):
- Superficial incisional – skin and subcutaneous tissue
- Deep incisional – fascia and muscle layers
- Organ/space infections – any part of the anatomy that was opened during surgery (e.g., peritoneal cavity)
Pathogenesis and Contributing Factors
- Microbial factors:
- Pathogenicity and virulence
- Microbial load > 10⁵ organisms per gram of tissue → critical threshold
- Incubation period – varies by organism and host status
- Host- related factors:
- Tissue necrosis
- Foreign bodies or implants
- Hypotension (poor perfusion)
- Nutritional status, anemia, diabetes, immunosuppression
- External (surgical) factors:
- Duration of surgery > 2 hrs
- Emergency procedures
- Poor surgical technique
- Inadequate aseptic precautions
Types of Surgical Wounds and Infection Risk
Risk Factors
- Advanced age, obesity
- Diabetes, cancer, immunosuppression
- Malnutrition, anemia, hypoxia
- Smoking
- Duration of surgery > 2 hours
- Emergency operations
- Foreign materials (e.g., sutures, implants)
- Inadequate aseptic technique
Clinical Features / Symptoms
- Redness (erythema)
- Pain and tenderness at the wound site
- Swelling, induration
- Fever
- Delayed wound healing
- Purulent discharge
Prevention (Prophylaxis)
- Strict adherence to aseptic and antiseptic techniques
- Proper surgical technique
- Pre- op skin cleansing
- Antibiotic prophylaxis (based on surgical category)
- Hand hygiene
- Sterilization of instruments
Treatment
- Antibiotics: Empirical → targeted based on culture
- Surgical drainage: For abscesses or deep infections
- Wound debridement: If necrotic tissue is present
- Supportive care:
- Fluid- electrolyte balance
- Nutrition optimization
- Additional surgery: If infection threatens underlying structures