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Contaminated Wound SSI Risk — SCE Infectious Diseases MCQ

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EasyInfection Prevention & ControlContaminated Wound SSI RiskSCE Infectious Diseases

A 50-year-old man develops a surgical site infection after emergency laparotomy for perforated diverticulitis. He was given appropriate surgical antibiotic prophylaxis at induction. Post-operatively, he develops a wound infection on day 5. What is the most important risk factor for SSI in this scenario?

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Correct answer: B — Contaminated surgical field (perforated viscus with faecal peritonitis) — contaminated/dirty wounds have SSI rates of 15–40% despite appropriate prophylaxis

The CDC wound classification system stratifies SSI risk: Clean (1–3%), Clean-Contaminated (3–10%), Contaminated (10–20%), Dirty (15–40%). Perforated diverticulitis with faecal peritonitis is a dirty/contaminated procedure — SSI rates of 15–40% are expected even with optimal prophylaxis, skin preparation, and surgical technique. Antibiotic prophylaxis reduces but cannot eliminate SSI risk in contaminated cases. Post-operative wound management (VAC therapy, delayed primary closure) may reduce SSI in contaminated wounds.

Reference: NICE NG125 2020 – SSI prevention; CDC 2017 – SSI guidelines