Original Investigation Repeated Peritoneal Dialysis–Associated Peritonitis: A Multicenter Registry Study Thulasi Thirugnanasambathan, MD, 1,2 Carmel M. Hawley, MMed Sci, 1,2 Sunil V. Badve, 1,2 Stephen P. McDonald, PhD, 1,3 Fiona G. Brown, PhD, 1,4 Neil Boudville, MMed Sci, 1,5 Kathryn J. Wiggins, MD, 1,6 Kym M. Bannister, MD, 1,3 Philip Clayton, MD, 1,7 and David W. Johnson, PhD 1,2 Background: Determinants and outcomes of peritoneal dialysis (PD)-associated peritonitis occurring within 4 weeks of completion of therapy of a prior episode caused by the same (relapse) or different organism (recurrence) recently have been characterized. However, determinants and outcomes of peritonitis occurring more than 4 weeks after treatment of a prior episode caused by the same (repeated) or different organism (nonrepeated) are poorly understood. Study Design: Observational cohort study using Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) data. Setting & Participants: All Australian PD patients between October 1, 2003, and December 31, 2007, with first episodes of repeated or nonrepeated peritonitis. Predictors: Repeated versus nonrepeated peritonitis, according to International Society of PD (ISPD) criteria. Outcomes & Measurements: Relapse, hospitalization, catheter removal, hemodialysis transfer, and death. Results: After a peritonitis episode, the probability that a subsequent episode represented repeated rather than nonrepeated peritonitis was highest in the second month (41%), then progressively decreased to a stable level of 14% from 6 months onward. When first episodes of repeated (n = 245) or nonrepeated peritonitis (n = 824) were analyzed, repeated peritonitis was predicted independently by a shorter elapsed time from the prior episode (adjusted OR per day elapsed, 0.91; 95% CI, 0.88-0.94). Staphylococcus aureus and coagulase- negative staphylococcus were isolated more frequently in repeated peritonitis, whereas Gram-negative, streptococcal, and fungal organisms were recovered more frequently in nonrepeated peritonitis. Using multivariate logistic regression, repeated peritonitis was associated independently with higher relapse (OR, 5.41; 95% CI, 3.72-7.89) and lower hospitalization rates (OR, 0.63; 95% CI, 0.46-0.85), but catheter removal, hemodialysis transfer, and death rates similar to nonrepeated peritonitis. Limitations: Limited covariate adjustment. Residual confounding and coding bias could not be excluded. Conclusions: Repeated and nonrepeated peritonitis episodes are caused by different spectra of micro- organisms and have different outcomes. Study findings suggest that the ISPD definition for repeated peritonitis should be limited to 6 months. Am J Kidney Dis. 59(1):84-91. Crown Copyright © 2011 Published by Elsevier Inc. on behalf of the National Kidney Foundation, Inc. All rights reserved. INDEX WORDS: Antibiotics; bacteria; fungus; microbiology; peritoneal dialysis; peritonitis; outcomes; recur- rence; relapse. P eritonitis is a serious complication of peritoneal dialysis (PD) that causes substantial morbidity and is to blame for 30% of technique failures and 21% of infectious deaths in PD patients in Australia and New Zealand. 1 Studies of organism-specific peritoni- tis 2-12 found that multiple peritonitis episodes are com- mon, with repeated peritonitis occurring in a significant proportion of patients with peritonitis caused by Staphy- lococcus aureus and peritonitis caused by coagulase- negative staphylococcus, whereas history of a previous episode of peritonitis was less common with peritonitis caused by Streptococcus and Pseudomonas species. In From the 1 Australia and New Zealand Dialysis and Transplant Registry, Adelaide; 2 Department of Renal Medicine, University of Queensland at Princess Alexandra Hospital, Brisbane; 3 Central Northern Adelaide Renal and Transplantation Service, Adelaide; 4 Department of Nephrology, Monash Medical Center, Clayton, Victoria; 5 Department of Medicine, University of Western Austra- lia, Perth; 6 Department of Renal Medicine, Royal Melbourne Hospital, Parkville and Eastern Health Integrated Renal Service, Box Hill; and 7 Department of Renal Medicine, Royal Prince Alfred Hospital, Sydney, Australia. Received February 1, 2011. Accepted in revised form June 3, 2011. Originally published online August 17, 2011. Address correspondence to David W. Johnson, PhD, Depart- ment of Nephrology, Level 2, ARTS Bldg, Princess Alexandra Hospital, Ipswich Rd, Woolloongabba, Brisbane Qld 4102, Austra- lia. E-mail: david_johnson@health.qld.gov.au Crown Copyright © 2011 Published by Elsevier Inc. on behalf of the National Kidney Foundation, Inc. All rights reserved. 0272-6386/$36.00 doi:10.1053/j.ajkd.2011.06.018 Am J Kidney Dis. 2012;59(1):84-91 84