Background: The study aim was to examine the frequency, predictors, treatment, and clinical outcomes of peritoneal dialysis-associated polymicrobial peritonitis. Study Design: Observational cohort study using ANZDATA (The Australia and New Zealand Dialysis and Transplant Registry) data. Setting & Participants: All Australian peritoneal dialysis patients between October 2003 and December 2006. Predictors: Age, sex, race, body mass index, baseline renal function, late referral, kidney disease, smoking status, comorbidity, peritoneal permeability, center, state, organisms, and antibiotic regimen. Outcomes & Measurements: Polymicrobial peritonitis occurrence, relapse, hospitalization, catheter removal, hemodialysis transfer, and death. Results: 359 episodes of polymicrobial peritonitis occurred in 324 individuals, representing 10% of all peritonitis episodes during 6,002 patient-years. The organisms isolated included mixed Gram-positive and Gram-negative organisms (41%), pure Gram-negative organisms (22%), pure Gram-positive organisms (25%), and mixed bacteria and fungi (13%). There were no significant independent predictors of polymicrobial peritonitis except for the presence of chronic lung disease. Compared with single-organism infections, polymicrobial peritonitis was associated with higher rates of hospitalization (83% vs 68%; P < 0.001), catheter removal (43% vs 19%; P < 0.001), permanent hemodialysis transfer (38% vs 15%; P < 0.001), and death (4% vs 2%; P = 0.03). Isolation of fungus or Gram-negative bacteria was the primary predictor of adverse clinical outcomes. Pure Gram-positive peritonitis had the best clinical outcomes. Patients who had their catheters removed >1 week after polymicrobial peritonitis onset were significantly more likely to be permanently transferred to hemodialysis therapy than those who had earlier catheter removal (92% vs 81%; P = 0.05). Limitations: Limited covariate adjustment. Residual confounding and coding bias could not be excluded. Conclusions: Polymicrobial peritonitis can be treated successfully using antibiotics alone without catheter removal in most cases, particularly when only Gram-positive organisms are isolated. Isolation of Gram-negative bacteria (with or without Gram-positive bacteria) or fungi carries a worse prognosis and generally should be treated with early catheter removal and appropriate antimicrobial therapy.
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