Staphylococcus Aureus Peritonitis in Australian Peritoneal Dialysis Patients: Predictors, Treatment, and Outcomes in 503 Cases

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Abstract
Staphylococcus aureus peritonitis is a serious complication of peritoneal dialysis (PD). Since reports of the course and treatment of S. aureus peritonitis have generally been limited to small, single-center studies, the aim of the current investigation was to examine the frequency, predictors, treatment, and clinical outcomes of this condition in all 4675 patients receiving PD in Australia between 1 October 2003 and 31 December 2006. 3594 episodes of peritonitis occurred in 1984 patients and 503 (14%) episodes of S. aureus peritonitis occurred in 355 (8%) individuals. 273 (77%) patients experienced 1 episode of S. aureus peritonitis, 52 (15%) experienced 2 episodes, 19 (5%) experienced 3 episodes, and 11 (3%) experienced 4 or more episodes. The predominant antibiotics used as initial empiric therapy were vancomycin (61%) and cephazolin (31%). Once S. aureus was isolated and identified, the prescription of vancomycin did not appreciably change for methicillin-sensitive S. aureus (MSSA) peritonitis (59%) and increased for methicillin-resistant S. aureus (MRSA) peritonitis (84%). S. aureus peritonitis was associated with a higher rate of relapse than non-S. aureus peritonitis (20% vs 13%, p < 0.001) but comparable rates of hospitalization (67% vs 70%, p = 0.2), catheter removal (23% vs 21%, p = 0.4), hemodialysis transfer (18% vs 18%, p = 0.6), and death (2.2% vs 2.3%, p = 0.9). MRSA peritonitis was independently predictive of an increased risk of permanent hemodialysis transfer [odds ratio (OR) 2.11, 95% confidence interval (CI) 1.17 – 3.82] and tended to be associated with an increased risk of hospitalization (OR 2.00, 95% CI 0.96 – 4.19). The initial empiric antibiotic choice between vancomycin and cephazolin was not significantly associated with clinical outcomes, but serious adverse outcomes were more likely if vancomycin was not used for subsequent treatment of MRSA peritonitis. In conclusion, S. aureus peritonitis is a serious complication of PD, involves a small proportion of patients, and is associated with a high rate of relapse and repeat episodes. Other adverse clinical outcomes are similar to those for peritonitis overall but are significantly worse for MRSA peritonitis. Empiric initial therapy with either vancomycin or cephazolin results in comparable outcomes, provided vancomycin is prescribed when MRSA is isolated and identified.