Coagulase-negative staphylococcal peritonitis: outcomes of cephalosporin-resistant strains.

Peritoneal dialysis (PD) peritonitis and subsequent relapses are undesirable complications for patients requiring home peritoneal dialysis. Coagulase-negative staphylococci (CoNS) remain a common cause of peritonitis. Strains of CoNS are emerging that are resistant to cephalosporins. It has been suggested that, if sensitivity testing shows resistance to cephalosporin but the patient is improving on intraperitoneal cephalosporin, then there is no need to change the antibiotic. The rationale for this approach is that the intraperitoneal concentration of cephalosporin is higher than concentrations used in the microbiology laboratory to determine sensitivity or resistance. Previously, we reviewed a smaller number of cases of CoNS and noted that the relapse rate seemed greater for strains with cephalosporin "resistance" initially treated with cephalosporins. The present retrospective review looks at the incidence and treatment of CoNS peritonitis reported as resistant to cephalosporins in a large urban PD program between January 1, 2006, and August 31, 2009. During the study period, 200 new cases of peritonitis occurred, 65 of which (32.5%) were identified as CoNS. All were treated empirically with cefazolin (or vancomycin if allergic) for gram-positive coverage and either tobramycin or ceftazidime for gram-negative coverage. Of the 65 CoNS cases, 27 (41.5%) were sensitive to cefazolin; 38 (58.5%) were reported to be cephalosporin-resistant. Of the 38 episodes of CoNS reported as resistant, 10 were treated throughout with cephalosporin, and 28 either started with or were changed to vancomycin. Of the 28 treated with vancomycin only, 2 relapsed, which compares with 4 of 10 who were treated with cephalosporin throughout (Fisher exact test p = 0.03) Our study suggests that, although cephalosporin-resistant cases of CoNS initially resolve with cephalosporin treatment, they are indeed associated with a greater risk of relapse. Patients with CoNS peritonitis reported resistant to cefazolin may benefit from a change to vancomycin to reduce the risk of relapse.