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Enterococcal Peritonitis in Peritoneal Dialysis: The Danger from Within?

Peritonitis is a major source of morbidity and mortality in peritoneal dialysis (PD) patients (1–3) and continues to hamper more widespread use of this treatment modality for end-stage renal failure (4). In recent times, the incidence of gram-positive peritonitis caused by skin flora (mainly Staphylococcus) has significantly declined, probably because of improvements in connectology (5–7) and exit-site and nasal chemoprophylaxis (8–10). However, the incidence of gram-positive infections attributable to intestinal organisms such as Enterococcus has not improved (11,12) and has consequently increased in relative terms. At the same time, a worrying upward trend in antimicrobial-resistant enterococcal infections— particularly with regard to cephalosporins, ampicillin, and vancomycin—has been noted. Limited data are available regarding enterococcal peritonitis in patients receiving chronic PD, but recent studies have begun to shed some light on this often problematic clinical situation (Table 1). Several investigations in the 1990s (13,14) and early 2000s (12) reported that enterococcal peritonitis was an infrequent cause of PD peritonitis (up to 8% of all cases) and that it was associated with older patient age, poorer response to empiric antibiotics (including ampicillin), higher rates of hospitalization, higher rates of relapse and repeat peritonitis, and higher rates of death than were seen with gram-positive infections. Absolute rates of enterococcal peritonitis were not reported, except by Kim et al. (12), who observed an enterococcal peritonitis rate of 0.007 episodes per patient–year (Table 1). In 2010, Edey et al. (15) reported an analysis of peritonitis as recorded in the Australian and New Zealand Dialysis and Transplant (ANZDATA) Registry database between October 2003 and December 2006 (Table 1). In their study, enterococcal infection accounted for 3.2% of all cases of peritonitis, with an absolute rate of 0.02 episodes per patient–year and a single-organism rate of 0.01 episodes per patient–year. The key findings were that, although enterococcal peritonitis tended to be associated with older age, there were no demographic or clinical characteristics that reliably predicted the isolation of enterococci from dialysate. Moreover, nearly half of all cases of enterococcal peritonitis (45%) were associated with the isolation of other organisms. Only 8% of cases were treated with intraperitoneal ampicillin in line with the 2005 and 2010 recommendations from the International Society for Peritoneal Dialysis (1,16), but 78% were treated with vancomycin monotherapy despite concerns regarding the possible emergence of vancomycin-resistant enterococci (VRE). Pure enterococcal peritonitis had outcomes similar to those in non-enterococcal or Staphylococcus aureus infections, but the isolation of additional organisms was associated with a fall in the antibiotic cure rate to 40% from 59%. Importantly, timely removal of the PD catheter (within 1 week of the onset of refractory enterococcal peritonitis) was associated with a significant reduction (to 74% from 100%) in the risk of permanent transfer to hemodialysis. A major limitation of this group’s investigation was the lack of available data pertaining to the antimicrobial susceptibilities of the enterococci isolated. That limitation was recently addressed in children by Sutherland et al. (17), who reported on the clinical characteristics, treatment, antimicrobial susceptibilities, and outcomes of 20 cases of enterococcal peritonitis recorded in the International Pediatric Peritonitis Registry (Table 1). In that series, enterococcal peritonitis accounted for 5.9% of peritonitis episodes. All 20 patients developed peritonitis despite the use of prophylactic antibiotic therapy at the exit site, and Enterococcus was isolated from skin in 1 patient. Resistance to ampicillin, first-generation cephalosporins, third-generation cephalosporins, gentamicin, and vancomycin was observed in 31%, 95%, 85%, 43%, and 21% of episodes respectively. However, despite the high level of resistance to cephalosporins and not-insignificant resistance to vancomycin in vitro, patients who had received empiric treatment with those antibiotics did very well, and overall, outcomes were excellent. Only 1 catheter had to be removed, all patients remained on PD, and all experienced a fully functional recovery. Those results stood in stark contrast to gram-negative peritonitis episodes, in which the in vitro susceptibility to antibiotics closely matched the clinical picture. In this issue of Peritoneal Dialysis International, Yip et al. (18) present a retrospective, single-center study focusing on the clinical course and outcomes of 29 cases of enterococcal peritonitis in 23 PD patients (Table 1). In