A 32-year-old man undergoes elective abdominal surgery for peptic ulcer perforation repair. On postoperative day 5, the surgical wound shows signs of infection with purulent discharge and erythema. Culture reports are pending. What is the drug of choice for empiric coverage of surgical site infection in this patient?

Explanation

## Empiric Coverage of Surgical Site Infection (SSI) ### Clinical Context Postoperative SSI in abdominal surgery typically involves polymicrobial flora including gram-positive cocci (Staphylococcus aureus), gram-negative bacilli (E. coli, Klebsiella), and anaerobes (Bacteroides, Clostridium). ### Drug of Choice Rationale **Key Point:** Ceftriaxone + Metronidazole is the preferred empiric regimen for established abdominal SSI because it provides: - Broad gram-negative coverage (ceftriaxone) - Anaerobic coverage (metronidazole) - Excellent tissue penetration into wound and peritoneal cavity ### Comparison of Options | Agent | Coverage | Use Case | Limitation | |-------|----------|----------|-------------| | Cefazolin | Gram-positive, some gram-negative | Prophylaxis only | Inadequate anaerobic coverage for established SSI | | Ceftriaxone + Metronidazole | Gram-positive, gram-negative, anaerobes | Empiric treatment of established SSI | Gold standard | | Penicillin G | Gram-positive, anaerobes | Outdated | Poor gram-negative coverage | | Fluoroquinolone monotherapy | Gram-negative, limited gram-positive | Oral step-down only | Inadequate anaerobic and gram-positive coverage | ### High-Yield Facts **High-Yield:** Cefazolin is appropriate for *surgical prophylaxis* (given preoperatively), but once SSI is established and culture results are pending, broader empiric coverage is mandatory. **Clinical Pearl:** The addition of metronidazole is critical because anaerobic organisms are common in abdominal SSI and cephalosporins alone do not reliably cover them. **Mnemonic:** **ABCD of SSI coverage** — **A**naerobes (metronidazole), **B**road gram-negative (cephalosporin), **C**ephalosporin choice (3rd generation), **D**epth of tissue penetration.