Which perioperative antibiotic regimen provides gram-negative and anaerobic coverage for GI surgeries?

• A. Cefazolin
• B. Gentamicin
• C. Ciprofloxacin and Metronidazole
• D. Amoxicillin-Clavulanate

Answer: (C)

The key idea is that preventing infection in GI surgery requires covering both the gram-negative enteric bacteria and the anaerobic organisms that dominate the gut. Metronidazole is highly effective against anaerobes, including Bacteroides species, while ciprofloxacin provides broad coverage against many gram-negative intestinal rods such as E. coli and Klebsiella. Together, they address the two main bacterial groups likely to cause postoperative intra-abdominal infections. The other regimens either lack anaerobic activity, or rely on a single agent that doesn’t adequately cover both classes, making them less reliable for GI surgical prophylaxis.