A patient with bowel perforation is prepped for surgery. Which antibiotic regimen provides appropriate prophylaxis?

• A. Cefoxitin and gentamicin
• B. Vancomycin and penicillin G
• C. Nafcillin, gentamicin, and metronidazole
• D. Metronidazole, clindamycin, and cefoxitin

Answer: (C)

When preparing for surgery after bowel perforation, you want antibiotic coverage that spans skin flora, enteric gram-negative bacteria, and anaerobes from the gut. The best regimen brings together agents that cover each of these groups: a penicillinase-stable penicillin to guard against Staphylococcus aureus (skin flora), an aminoglycoside for aerobic gram-negative rods, and an anaerobic agent for gut bacteria.

Nafcillin targets MSSA effectively, providing solid skin flora coverage. Gentamicin adds robust aerobic gram-negative coverage, including Enterobacterales that you’d encounter with intra-abdominal contamination. Metronidazole specifically tackles anaerobes such as Bacteroides species, which are abundant in bowel contents. Together, they form a broad, balanced prophylaxis against the bacteria most likely to cause postoperative infection in bowel perforation.

Other regimens either lack reliable gram-negative or anaerobic coverage, rely on agents with limited activity against key organisms, or introduce redundancy or risks (for example, unnecessary overlap in anaerobic coverage or poor coverage of skin flora).