What is the antibiotic of choice for Spontaneous Bacterial Peritonitis (SBP)?

Antibiotic of Choice for Spontaneous Bacterial Peritonitis (SBP)

Third-generation cephalosporins—specifically cefotaxime 2g IV every 8-12 hours or ceftriaxone 1-2g IV every 12-24 hours—are the first-line antibiotics for community-acquired SBP and should be started immediately upon diagnosis. 1, 2

Community-Acquired SBP: First-Line Treatment

• Cefotaxime 2g IV every 8-12 hours for 5-7 days is the most extensively studied regimen with infection resolution rates of 77-98% 3, 1, 4
• A dose of 4g/day (2g every 12 hours) is as effective as 8g/day (2g every 6 hours), and 5 days of therapy is as effective as 10 days 3, 4
• Ceftriaxone 1-2g IV every 12-24 hours is an equally acceptable alternative third-generation cephalosporin 1
• These agents target the most common causative organisms: Gram-negative aerobic bacteria, particularly E. coli 3, 5

Alternative Antibiotics for Specific Scenarios

For Uncomplicated Community-Acquired SBP in Stable Patients:

• Oral ofloxacin 400mg every 12 hours achieves 84% infection resolution, comparable to IV cefotaxime, but only for patients who are hemodynamically stable, not septic, and have no recent antibiotic exposure 3, 1
• Oral ciprofloxacin 500mg every 12 hours can be used as step-down therapy after 2 days of IV treatment or as initial therapy in highly selected stable patients 1

Critical Caveat on Quinolones:

• Never use quinolones in patients already on quinolone prophylaxis, in areas with high quinolone resistance, or for nosocomial SBP 3, 1, 2

For Patients with Penicillin Allergy:

• Amoxicillin/clavulanic acid 1g/0.2g IV every 8 hours (then switch to 0.5g/0.125g PO every 8 hours) achieves 87% resolution rates, similar to cefotaxime 3, 1

Nosocomial or Healthcare-Associated SBP: Broader Coverage Required

For nosocomial SBP, use meropenem 1g IV every 8 hours plus daptomycin 6mg/kg/day in settings with high multidrug-resistant organism (MDRO) prevalence, particularly for ICU patients, recent hospitalization, or septic shock 1, 6

• This combination is significantly more effective than ceftazidime (86.7% vs. 25% resolution rate) for nosocomial SBP 6
• Nosocomial SBP now has a 35% MDRO rate, requiring broader initial coverage 1
• Consider piperacillin-tazobactam as an alternative for nosocomial cases 7

Mandatory Adjunctive Therapy: IV Albumin

IV albumin is not optional—it must be given alongside antibiotics to reduce mortality and prevent hepatorenal syndrome 1, 8, 2

• Dosing regimen: 1.5 g/kg at diagnosis (within 6 hours), then 1.0 g/kg on day 3 3, 1, 8
• This reduces hepatorenal syndrome from 30% to 10% and mortality from 29% to 10% 3, 1, 8
• Albumin is particularly critical in patients with baseline bilirubin ≥4 mg/dL or creatinine ≥1 mg/dL 3

Monitoring Treatment Response

• Perform repeat paracentesis at 48 hours to assess treatment efficacy 3, 1, 2
• Treatment success is defined as ascitic neutrophil count decreasing to <25% of pre-treatment value 3, 1, 2
• If neutrophil count fails to decrease adequately, suspect treatment failure due to resistant bacteria or secondary peritonitis 3, 2

Critical Pitfalls to Avoid

• Never delay antibiotics waiting for culture results—empirical therapy must start immediately upon diagnosis based on neutrophil count >250/mm³ alone 1, 2
• Avoid aminoglycosides (e.g., tobramycin) due to nephrotoxicity risk in cirrhotic patients 1, 8
• Do not use quinolones in patients on quinolone prophylaxis—switch to cefotaxime or amoxicillin/clavulanic acid 2
• Each hour of delay in antibiotic administration increases mortality by 3.3-10% in cirrhotic patients with septic shock 8, 2

Treatment Duration

• 5-7 days of antibiotic therapy is sufficient for most cases of SBP 3, 1, 2
• Five days is as effective as 10 days for uncomplicated SBP 2, 4
• For septic shock, treat for 7-10 days and narrow coverage once culture sensitivities are available 8