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Surgical site infection and its prevention
Most surgical site infections are prevented by simple measures — a single prophylactic antibiotic dose within 60 minutes before incision, chlorhexidine-alcohol skin preparation, clipping rather than razor shaving, and keeping temperature and glucose normal — and a superficial infection is treated by opening the wound, not by antibiotics alone.
Why it matters in the exam
The exam asks about prevention in detail: which antibiotic (cefazolin for most operations, with anaerobic cover added for colorectal surgery), when to give it (within 60 minutes before incision; vancomycin within 120 minutes), when to re-dose (a long operation or major blood loss) and how long to continue (no longer than 24 hours — and usually not after wound closure). Candidates are also asked about wound classification — clean, clean-contaminated, contaminated and dirty — and how it relates to the risk of infection.
The second part is diagnosis and treatment: a wound infection usually appears on days 5–7 after surgery, with redness, fever and discharge; a superficial infection is treated by opening and draining, and antibiotics are added only for surrounding cellulitis or systemic signs. A deep or intra-abdominal infection is diagnosed by CT and drained. It is especially important to recognise necrotising soft-tissue infection — pain out of proportion to the appearance, oedema beyond the redness, bullae, crepitus and rapid deterioration — which needs urgent surgical debridement and broad antibiotics. Another classic question is salmon-pink discharge from the wound on days 5–8, which heralds fascial dehiscence.
Key points
- Cefazolin within 60 minutes before incision; for the colon add anaerobic cover.
- Repeat dose after 4 hours or 1500 mL of blood loss; stop within 24 hours.
- Chlorhexidine-alcohol, no razor shaving, normal temperature and glucose below 200 mg/dL.
- Wound infection (days 5–7) — open and drain; deep abscess — CT and percutaneous drainage.
- Necrotising infection — urgent surgical debridement and broad antibiotics.
Summary table
| Wound class | Example | Antibiotic prophylaxis |
|---|---|---|
| Clean (I) | Hernia without mesh, thyroid surgery | Usually not needed; needed when an implant is placed (mesh, joint) |
| Clean-contaminated (II) | Cholecystectomy, elective bowel surgery | Cefazolin; for the colon add metronidazole (and nowadays oral antibiotics with bowel preparation) |
| Contaminated (III) | Spillage from the bowel, fresh traumatic wound, inflamed appendix | Prophylaxis, and sometimes treatment according to the finding |
| Dirty (IV) | Faecal perforation, abscess, dead tissue | Antibiotic treatment (not prophylaxis) and source control; sometimes the skin is left open |
| Timing and dose | Cefazolin 2 g (3 g above 120 kg) within 60 minutes before incision; repeat every 4 hours or after blood loss over 1500 mL | Stop within 24 hours |
Free exam questions
בן 80 ?, מועמד לניתוח אלקטיבי של כריתת כיס מרה. מה מומלץ (the question as examined, in Hebrew)
- א. מתן מנה בודדת של Cefazolin כחצי שעה לפני התחלת הניתוח
- ב. מתן ceftriaxone מיום הניתוח למשך 48 שעות
- ג. מתן cephalexin כשעתיים לפני הניתוח למשך 24 שעות
- ד. מתן מנה בודדת של cefoxitin כשעתיים לפני הניתוח
איזה מהגורמים הבאים מהווה גורם סיכון ל- fascial dehiscence ?לאחר לפרוטומיה (the question as examined, in Hebrew)
- א. מיימת
- ב. אי ספיקת כליות
- ג. אי ספיקת לב
- ד. המופיליה
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Sources
- CDC Guideline for the Prevention of Surgical Site Infection, 2017 — Antimicrobial prophylaxis, glycaemic control, normothermia and skin preparation
- ASHP/IDSA/SIS/SHEA Clinical practice guidelines for antimicrobial prophylaxis in surgery, 2013 — Agent choice, timing, re-dosing and duration
- WSES/SIS-E guidelines for the management of skin and soft-tissue infections (necrotising soft-tissue infections), 2018 — Diagnosis and debridement
- Sabiston Textbook of Surgery, 21st edition (2022) — Surgical Infections and Antibiotic Use
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.