A 52-year-old man undergoes elective open cholecystectomy for cholelithiasis. On postoperative day 5, he develops erythema, warmth, and purulent discharge from the surgical wound. Wound culture grows Staphylococcus aureus. The wound edges are indurated and there is no fluctuance. What is the primary pathophysiological defect responsible for this complication?

Explanation

## Surgical Site Infection (SSI) — Pathophysiology **Key Point:** Postoperative day 5 wound infection with purulent discharge indicates failure of the **inflammatory phase** of wound healing (Days 0–5), specifically impaired bacterial clearance. ### Timeline of Wound Healing Phases: | Phase | Duration | Key Events | Failure → Complication | |-------|----------|-----------|------------------------| | **Inflammatory** | 0–5 days | Hemostasis, neutrophil infiltration, bacterial clearance | SSI (impaired PMN function/recruitment) | | **Proliferative** | 5–21 days | Angiogenesis, collagen deposition, granulation tissue | Delayed healing, poor tensile strength | | **Remodeling** | 21 days–2 years | Collagen cross-linking, scar maturation | Hypertrophic scars, contractures | **Clinical Pearl:** S. aureus is a common skin flora; SSI on POD 5 reflects **inadequate neutrophil-mediated bacterial control** during the acute inflammatory response. Neutrophils are the primary defense against bacterial colonization in the first 5 days. **High-Yield:** Risk factors for impaired inflammatory phase include: - Diabetes (impaired PMN chemotaxis and phagocytosis) - Immunosuppression - Malnutrition (zinc, vitamin C deficiency) - Hypoxia at wound site **Mnemonic:** **SHINE** for SSI prevention: **S**terility, **H**emostasis, **I**mmunity (optimize), **N**utritional status, **E**xperience (surgical technique).