Empiric Antibiotic for Suspected SBP with Ascitic Neutrophil Count 455 cells/µL
Start intravenous cefotaxime 2 grams every 8 hours or ceftriaxone 1-2 grams every 12-24 hours immediately, without waiting for cytology results, because the ascitic neutrophil count of 455 cells/µL exceeds the diagnostic threshold of 250 cells/µL for spontaneous bacterial peritonitis. 1, 2, 3
Rationale for Immediate Third-Generation Cephalosporin Therapy
The presence of peritoneal carcinomatosis does not change the empiric antibiotic approach when the ascitic neutrophil count is elevated above 250 cells/µL. 1, 2
Third-generation cephalosporins remain first-line therapy for community-acquired SBP, achieving infection resolution rates of 77-98% for cefotaxime and 73-100% for ceftriaxone. 1, 2, 3
Cefotaxime dosing: 2 grams IV every 8 hours provides optimal coverage; a total daily dose of 4 grams (every 12 hours) is clinically equivalent to 8 grams/day, but the every-8-hour schedule ensures more consistent drug levels. 1, 4
Ceftriaxone dosing: 1-2 grams IV every 12-24 hours is equally effective as cefotaxime and may be more convenient. 2, 3, 5
Treatment duration: 5 days is sufficient for uncomplicated cases and is as effective as 10 days. 1, 2, 3
Critical Adjunctive Therapy: IV Albumin
Administer IV albumin 1.5 g/kg body weight within 6 hours of diagnosis, followed by 1.0 g/kg on day 3 to reduce hepatorenal syndrome from 30% to 10% and mortality from 29% to 10%. 1, 2, 3
- This albumin regimen is mandatory for patients with high-risk features (serum creatinine ≥1 mg/dL, BUN ≥30 mg/dL, or total bilirubin ≥4 mg/dL). 1, 2
Monitoring Treatment Response
Perform repeat paracentesis at 48 hours to assess treatment efficacy by measuring the ascitic neutrophil count. 1, 2, 3
Treatment success is defined as a ≥75% reduction in ascitic neutrophil count (i.e., PMN count <25% of baseline value). 1, 2
Treatment failure is suspected if the neutrophil count fails to decrease by at least 25% at 48 hours, which should prompt broadening of antibiotic coverage and investigation for secondary peritonitis or resistant organisms. 1, 2
Distinguishing SBP from Secondary Peritonitis
While awaiting cytology results, monitor for features suggesting secondary peritonitis rather than SBP:
- Ascitic total protein >1 g/dL 1, 2
- Ascitic LDH above the upper limit of normal for serum 1, 2
- Ascitic glucose <50 mg/dL 1, 2
- Polymicrobial culture growth 1, 2
When ≥2 of these criteria are present, obtain CT imaging to rule out gastrointestinal perforation, add anaerobic coverage, and obtain surgical consultation. 1, 2
Important Clinical Caveats
Never delay antibiotics waiting for cytology or culture results—empirical therapy must start immediately upon diagnosis (PMN >250/mm³). 1, 2, 3
Avoid aminoglycosides (e.g., tobramycin, gentamicin) due to nephrotoxicity and inferior efficacy compared to cefotaxime. 1, 2
Do not use quinolones as first-line therapy if the patient has received quinolone prophylaxis, presents with severe disease (shock, renal failure, encephalopathy), or has nosocomial acquisition, due to high resistance rates. 1, 2
The concern for peritoneal carcinomatosis does not alter the initial antibiotic choice; malignant ascites can coexist with SBP, and the elevated neutrophil count mandates treatment for infection. 1
Nosocomial vs. Community-Acquired Considerations
If this is nosocomial or healthcare-associated SBP (ICU setting, recent hospitalization, or septic shock), consider broader-spectrum coverage with meropenem 1 gram IV every 8 hours plus daptomycin 6 mg/kg/day due to higher rates of multidrug-resistant organisms (35% MDRO rate in nosocomial SBP). 1, 6
For community-acquired SBP, third-generation cephalosporins remain the gold standard. 1, 2, 3, 7