What is the initial antibiotic treatment for peritonitis in a patient undergoing peritoneal (PD) dialysis?

Initial Antibiotic Treatment for Peritoneal Dialysis-Associated Peritonitis

For peritoneal dialysis-associated peritonitis, empirical therapy should consist of intraperitoneal vancomycin (or a first-generation cephalosporin) combined with ceftazidime or an aminoglycoside, initiated immediately upon diagnosis without waiting for culture results. 1, 2

Diagnostic Confirmation Before Treatment

• Peritonitis is confirmed by a peritoneal dialysate PMN count >100 cells/mm³ (with >50% neutrophils) or cloudy dialysate effluent with abdominal pain 1, 3
• Collect peritoneal fluid for culture before initiating antibiotics, with bedside inoculation into blood culture bottles to maximize sensitivity 1
• Obtain simultaneous blood cultures to increase organism isolation rates 1

First-Line Empirical Antibiotic Regimens

The optimal empirical regimen is vancomycin plus ceftazidime administered intraperitoneally, which achieves an 86% resolution rate—significantly superior to first-generation cephalosporin plus aminoglycoside (66%) or vancomycin plus aminoglycoside (75%) 2, 4

Specific Dosing Recommendations:

• Vancomycin: 15-30 mg/kg intraperitoneally in one exchange per week (loading dose: 1000 mg/L in one exchange) 3, 4
• Ceftazidime: 1000-1500 mg/L loading dose, then 125-250 mg/L maintenance dose in each exchange 3, 4

Alternative Regimen:

• First-generation cephalosporin (cefazolin) plus aminoglycoside (gentamicin) can be used but has lower efficacy 2
  • Cefazolin: 500 mg/L loading dose, then 125 mg/L maintenance
  • Gentamicin: 0.6 mg/kg intraperitoneally 3

Route of Administration

• Intraperitoneal administration is strongly preferred over intravenous or oral routes for PD peritonitis, as it achieves superior local drug concentrations 1, 3
• Continuous ambulatory peritoneal dialysis (CAPD) patients: add antibiotics to each exchange
• Automated peritoneal dialysis (APD) patients: use one long-dwell exchange daily with antibiotics 3

Treatment Duration and Monitoring

• Continue antibiotics for 14 days for gram-positive infections and 21 days for gram-negative infections 3
• Perform repeat cell count and culture at 48-72 hours to assess treatment response 1
• Treatment failure is defined as failure of dialysate to clear or PMN count not decreasing by ≥25% after 48 hours 1

Adjustments Based on Culture Results

For Gram-Positive Organisms:

• Continue vancomycin or switch to first-generation cephalosporin if methicillin-sensitive 3, 5
• For vancomycin-resistant enterococci, consider linezolid, quinupristin/dalfopristin, or daptomycin 5

For Gram-Negative Organisms:

• Continue ceftazidime or switch based on sensitivities 3
• For ESBL-producing organisms, carbapenems may be necessary 5
• For Pseudomonas: continue ceftazidime or use fluoroquinolones 3

For Fungal Peritonitis:

• Immediate catheter removal is mandatory plus antifungal therapy (fluconazole or amphotericin B) for minimum 3 weeks, followed by transfer to hemodialysis 3

Critical Pitfalls to Avoid

• Never delay antibiotic initiation waiting for culture results—this significantly worsens outcomes 1, 3
• Avoid aminoglycosides in patients with residual renal function due to nephrotoxicity risk 3, 5
• Do not use quinolones as empirical therapy if the patient has received them for prophylaxis due to resistance 5
• Failure to remove catheter in fungal peritonitis results in treatment failure and mortality 3
• Not adjusting therapy based on local resistance patterns can lead to inadequate coverage 5, 6

When to Suspect Treatment Failure or Secondary Peritonitis

Suspect secondary (surgical) peritonitis if: 1

• Multiple organisms on Gram stain or culture
• Persistent symptoms despite appropriate antibiotics for 5 days
• Peritoneal fluid glucose <50 mg/dL and protein >1 g/dL
• Recurrent peritonitis with same organism within 4 weeks

These patients require urgent surgical evaluation and broader antibiotic coverage including anaerobic agents 1

Local Resistance Monitoring

• Each dialysis center must track local microbiology patterns and resistance rates to guide empirical therapy selection 5, 6
• The vancomycin-gentamicin combination maintains high susceptibility rates (98% and 92% respectively) without driving resistance over time 6
• Staphylococcus species (both aureus and coagulase-negative) remain the most common pathogens (60-70% of cases) 3, 6