What is the initial management for bacterial peritonitis?

Initial Management of Bacterial Peritonitis

The initial management of bacterial peritonitis requires immediate empirical broad-spectrum antibiotics started as soon as possible (ideally within the first hour), with the specific regimen determined by whether the infection is spontaneous bacterial peritonitis (SBP) in cirrhosis, secondary peritonitis from intra-abdominal pathology, or nosocomial/healthcare-associated infection. 1

Immediate Diagnostic Steps

Before initiating antibiotics, obtain peritoneal fluid for analysis and culture:

• Perform diagnostic paracentesis immediately with bedside inoculation of ascitic fluid into blood culture bottles to maximize culture sensitivity (>90%) 2
• Confirm diagnosis with peritoneal fluid PMN count >250 cells/mm³ 1, 2
• Send fluid for Gram stain, aerobic and anaerobic cultures, and antibiotic susceptibility testing 1
• Collect at least 1-2 mL of fluid or tissue in sterile, airless containers 1

First-Line Empirical Antibiotic Therapy

For Spontaneous Bacterial Peritonitis (SBP) in Cirrhosis

Third-generation cephalosporins are the first-line treatment for community-acquired SBP:

• Cefotaxime 2g IV every 6-8 hours is the gold standard regimen 1, 3
• Alternative: Ceftriaxone 1-2g IV daily 1
• Treatment duration: 5 days (as effective as 10 days) 1, 2

Critical adjunctive therapy - Intravenous albumin:

• Administer albumin 1.5 g/kg at diagnosis, followed by 1 g/kg on day 3 1, 2
• This significantly reduces hepatorenal syndrome incidence (from 30% to 10%) and mortality (from 29% to 10%) 1, 2
• Particularly essential in patients with baseline bilirubin ≥4 mg/dL or creatinine ≥1 mg/dL 1

Alternative oral regimen for uncomplicated cases:

• Ofloxacin 400 mg PO every 12 hours can be used if patient has no vomiting, shock, hepatic encephalopathy grade ≥II, or creatinine >3 mg/dL 1, 2

For Nosocomial or Healthcare-Associated SBP

Broader spectrum coverage is mandatory due to multidrug-resistant organisms (MDROs):

• Meropenem 1g IV every 8 hours PLUS daptomycin 6 mg/kg/day is significantly more effective than ceftazidime (86.7% vs 25% resolution rate) 4
• This combination addresses the high prevalence of cephalosporin-resistant gram-negative bacteria and gram-positive cocci (including Enterococcus) in nosocomial infections 3, 4
• Do NOT use quinolones in patients already on quinolone prophylaxis or in areas with high quinolone resistance 1, 3

For Secondary Peritonitis (Intra-Abdominal Source)

Empirical regimen must cover gram-negative, gram-positive, and anaerobic bacteria:

• Piperacillin-tazobactam 3.375g IV every 6 hours (or 4.5g every 6 hours for severe infections) 1, 5
• Alternative: Cefotaxime 2g IV every 6 hours PLUS metronidazole 1
• For high-risk patients or severe sepsis/septic shock: Consider carbapenems (imipenem, meropenem, or ertapenem) 1, 6
• Duration: 3-5 days or until inflammatory markers normalize for perforated peptic ulcer 1; 7-10 days for other sources 5

Risk Stratification for Antibiotic Selection

Community-acquired infections (low MDRO risk):

• Third-generation cephalosporins or beta-lactam/beta-lactamase inhibitors are appropriate 1
• Expected pathogens: E. coli (most common), Klebsiella, Streptococcus species 1, 3

Healthcare-associated or high MDRO risk (any of the following):

• ICU admission or hospitalization >1 week 1
• Previous antimicrobial therapy within 90 days 1
• Corticosteroid use, organ transplantation, or immunosuppression 1
• Known colonization with ESBL-producing Enterobacteriaceae 1
• For these patients, use carbapenems ± anti-MRSA coverage 1, 4

Monitoring Treatment Response

Perform repeat paracentesis at 48 hours:

• Treatment success: Ascitic neutrophil count decreases to <25% of pre-treatment value 1, 2
• Treatment failure: Worsening clinical signs, no marked reduction, or increase in PMN count 1

If treatment fails, consider:

• Resistant bacteria requiring antibiotic change based on culture results 1
• Secondary bacterial peritonitis requiring surgical evaluation 1, 2

Distinguishing Secondary from Spontaneous Peritonitis

Suspect secondary peritonitis if:

• Multiple organisms on Gram stain or culture 1, 2
• Ascitic total protein ≥1 g/dL 2
• Ascitic glucose ≤50 mg/dL 2
• PMN count >1,000/mm³ or increases despite treatment 2
• If suspected, obtain abdominal CT and surgical consultation immediately 2

Source Control

For secondary peritonitis, surgical intervention is mandatory:

• Control contamination source through resection, exclusion, or repair of diseased viscus 7
• Peritoneal toilet and drainage 7
• Timing: Emergency surgery as soon as patient is stabilized 1

Special Considerations

Antifungal therapy:

• Not routinely recommended for community-acquired perforated peptic ulcer 1
• Reserve for critically ill, severely immunocompromised patients, or healthcare-associated infections 1
• If indicated: Fluconazole until culture results available 6

Enterococcus coverage:

• Not routinely necessary for community-acquired infections 1
• Consider in patients with organ dysfunction, septic shock, or nosocomial infections 1, 6

Common Pitfalls to Avoid

• Delaying antibiotics while awaiting culture results - start empirically immediately 1
• Failing to administer albumin in SBP - this doubles mortality risk 1, 2
• Using quinolones in patients on quinolone prophylaxis - resistance is nearly universal 1, 3
• Inadequate coverage for nosocomial infections - third-generation cephalosporins fail in 75% of cases 4
• Not performing diagnostic paracentesis - clinical diagnosis alone is inadequate 2
• Missing secondary peritonitis - requires surgical intervention, not just antibiotics 1, 2