Surgical site infections

SSI Classification - Skin Deep or More

• Superficial Incisional SSI:
  • Involves only skin and subcutaneous tissue.
  • Occurs within 30 days post-procedure.
  • Presents with purulent drainage, positive cultures, or localized inflammation.
• Deep Incisional SSI:
  • Affects deep soft tissues (fascia, muscle).
  • Occurs within 90 days (no implant) or up to 1 year (with implant).
• Organ/Space SSI:
  • Involves any organ or anatomical space opened or manipulated during surgery.
  • Timeline is identical to Deep Incisional SSI.

⭐ Staphylococcus aureus is the most frequent pathogen isolated from SSIs.

Risk Factors & Bugs - Who's at Risk?

• Patient Factors:
  • Obesity (BMI > 30), smoking, malnutrition
  • Poorly controlled diabetes (HbA1c > 7%)
  • Immunosuppression (steroids, chemotherapy)
  • Nasal colonization with S. aureus
• Procedural Factors:
  • Wound classification (Dirty > Contaminated)
  • Prolonged duration, emergency surgery
  • Hypothermia, poor surgical technique
• Common Pathogens:
  • Staphylococcus aureus: Most common cause.
  • Coagulase-negative staphylococci: With prosthetic implants.
  • Gram-negatives/anaerobes (E. coli, Bacteroides): GI/GU surgery.

⭐ Rapidly progressing infections (<48 hrs) with severe pain and systemic signs suggest aggressive pathogens like S. pyogenes or Clostridium perfringens.

Prevention - Guarding the Gateway

• Pre-operative Prep:
  • Optimize patient: Control glucose (<180 mg/dL), cease smoking (4-6 wks prior), improve nutrition.
  • Pre-op shower with chlorhexidine gluconate (CHG).
  • Nasal mupirocin for known MRSA/MSSA carriers.
• Intra-operative Shield:
  • Antimicrobial Prophylaxis:
    • Administer within 60 mins before incision (120 mins for vancomycin/fluoroquinolones).
    • Common agent: Cefazolin.
    • Redose for long procedures or significant blood loss.
  • Aseptic Technique:
    • Skin prep: Chlorhexidine-alcohol preferred.
    • Maintain normothermia and glycemic control.
• Post-operative Care:
  • Sterile dressing for 24-48 hours.
  • Discontinue prophylactic antibiotics within 24 hours of surgery completion.

⭐ The most common organism causing SSIs is Staphylococcus aureus. Prophylactic antibiotics are not for treating infection but for reducing the bacterial burden at the time of incision.

Diagnosis & Treatment - Spot and Stop

• Diagnosis:
  • Clinical signs: New/worsening pain, erythema, induration, warmth, purulent drainage.
  • Systemic signs: Fever >38°C, leukocytosis.
  • Definitive: Wound culture & sensitivity.
  • Imaging (CT/US) for suspected deep/organ space abscesses.

• Treatment Algorithm:

• Antibiotics: Tailor to culture. Empiric therapy targets Staph aureus (Vancomycin for MRSA risk). For GI/GU source, add gram-negative & anaerobic coverage.

⭐ Most SSIs manifest 5-7 days post-op. Infection in the first 48 hours suggests highly virulent organisms like Streptococcus pyogenes (Group A Strep) or Clostridium perfringens.

High‑Yield Points - ⚡ Biggest Takeaways

• Staphylococcus aureus is the most common cause of surgical site infections (SSIs).
• Administer prophylactic antibiotics, usually Cefazolin, within 60 minutes before the initial incision.
• Use Vancomycin for prophylaxis in patients with a history of MRSA colonization.
• A new-onset fever occurring post-operative day 5 to 7 is highly suspicious for an SSI.
• The cornerstone of management is source control, including incision and drainage of any abscess.
• For colorectal surgeries, prophylaxis must cover gram-negative and anaerobic organisms.