## Antibiotic Choice in Acute Cholecystitis **Key Point:** Acute cholecystitis requires broad-spectrum coverage against gram-negative aerobes and anaerobes, particularly E. coli, Klebsiella, and Bacteroides species. ### Rationale for Ceftriaxone + Metronidazole Ceftriaxone is a third-generation cephalosporin with excellent biliary penetration and broad gram-negative coverage. Metronidazole provides anaerobic coverage essential in biliary infections. This combination is: - First-line empiric therapy in acute cholecystitis [cite:Harrison 21e Ch 308] - Covers the most common pathogens in biliary tract infections - Achieves high concentrations in bile and gallbladder tissue - Recommended by most surgical guidelines for community-acquired biliary infections ### Spectrum Comparison | Drug Combination | Gram-Negative | Gram-Positive | Anaerobes | Biliary Penetration | |---|---|---|---|---| | **Ceftriaxone + metronidazole** | ✓ Excellent | ✓ Good | ✓ Excellent | ✓ Excellent | | Amoxicillin-clavulanate | ✓ Moderate | ✓ Good | ✓ Moderate | ✓ Moderate | | Fluoroquinolone alone | ✓ Good | ✗ Poor | ✗ Poor | ✓ Good | | Clindamycin alone | ✗ Poor | ✓ Good | ✓ Good | ✓ Moderate | **Clinical Pearl:** In acute cholecystitis, anaerobic coverage is mandatory because bile is an anaerobic environment, and Bacteroides fragilis is commonly isolated. Monotherapy with agents lacking anaerobic coverage increases treatment failure risk. **High-Yield:** The classic empiric regimen for acute cholecystitis is **third-generation cephalosporin + metronidazole** or **piperacillin-tazobactam** (if Pseudomonas coverage needed). Fluoroquinolones alone are inadequate for anaerobes and should not be used as monotherapy.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.