A 48-year-old woman with cirrhosis presents with spontaneous bacterial peritonitis (SBP) confirmed by ascitic fluid analysis (PMN count 250/μL, positive culture for E. coli). What is the drug of choice for empirical antibiotic therapy?

Explanation

## Drug of Choice for Spontaneous Bacterial Peritonitis **Key Point:** Ceftriaxone (or cefotaxime) is the first-line empirical antibiotic for SBP due to broad gram-negative and gram-positive coverage with excellent ascitic fluid penetration. ### Pathophysiology of SBP SBP occurs in cirrhotic patients due to: - Impaired opsonization and complement function - Bacterial translocation from gut - Reduced ascitic fluid opsonic activity - Most common organisms: E. coli, Klebsiella, Streptococcus pneumoniae ### Antibiotic Selection Criteria | Criterion | Ceftriaxone | Ciprofloxacin | Amoxicillin-clavulanate | Cefotaxime | | --- | --- | --- | --- | --- | | **Gram-negative coverage** | Excellent | Good | Moderate | Excellent | | **Gram-positive coverage** | Good | Poor | Good | Good | | **Ascitic penetration** | Excellent | Good | Moderate | Excellent | | **Resistance patterns** | Low | Increasing | Moderate | Low | | **First-line status** | Yes | No | No | Yes (alternative) | **High-Yield:** Ceftriaxone 1 g IV/IM twice daily is the standard empirical choice. Cefotaxime is an equally effective alternative. ### Clinical Management Protocol **Diagnostic Criteria for SBP:** - Ascitic fluid PMN count ≥250 cells/μL - Positive culture (in ~50% of cases) - No evidence of secondary peritonitis (no perforation) **Treatment Duration:** 5–7 days of IV antibiotics, then transition to oral fluoroquinolone prophylaxis if recurrent. **Adjunctive Therapy:** - Albumin infusion (1.5 g/kg at diagnosis, 1 g/kg on day 3) reduces renal failure and mortality - Variceal prophylaxis if not already on β-blockers **Clinical Pearl:** SBP in a cirrhotic patient with ascites is a medical emergency with high mortality (~20% in-hospital). Early recognition and empirical antibiotics before culture results are critical. **Mnemonic:** **CEFTRI** — **C**eftriaxone for **E**mpyema, **F**luoroquinolone for **T**reatment-**R**esponse prophylaxis, **I**nclude albumin. **Warning:** Do NOT delay antibiotics awaiting culture results. Empirical therapy should start immediately upon clinical suspicion and diagnostic paracentesis. [cite:Harrison 21e Ch 297]