Intraperitoneal urokinase and oral rifampicin for persisting asymptomatic dialysate infection following acute coagulase-negative Staphylococcus peritonitis

BACKGROUND: Coagulase-negative staphylococcus (CoNS) is responsible for cases of refractory and relapsing peritonitis in peritoneal dialysis (PD) patients, probably by biofilm formation on the catheter. The ISPD recommends catheter removal in such cases. Urokinase has been used to dissolve the biofilm lining the PD catheter, thus favoring antibiotic efficacy. Rifampicin has shown its efficacy in penetrating CoNS biofilm. METHODS: We defined persisting asymptomatic CoNS dialysate infection as a peritonitis episode with clinical improvement within 48 hours and dialysate clearing, but with persisting positive dialysate cultures. We retrospectively analyzed the outcome of such cases observed between 1/1998 and 12/2007. In all cases, intraperitoneal (IP) urokinase (100 000 units) and oral rifampicin (600 mg every day for 3 weeks) were added to intravenous vancomycin. RESULTS: 33 cases of CoNS peritonitis were recorded and 11 of them (33.3%) met the criteria of persisting asymptomatic CoNS dialysate infection. All were initially treated with intravenous vancomycin and oral ciprofloxacin, according to our protocol. Dialysate clearing, defined by a white blood cell count <100/muL, was noted at day 8 (range 4 - 17 days) on average, while dialysate cultures were still positive a mean of 6 (range 0 - 16) days later [i.e., 13.9 (range 5 - 24) days after peritonitis onset]. IP urokinase instillation was performed an average of 18.9 (range 11 - 30) days after peritonitis onset. Treatment success, defined by peritonitis resolution with sterilization of the dialysate, without catheter removal and relapse peritonitis within 6 weeks of treatment completion, was observed in 7 of 11 (64%) cases. No side effects following IP urokinase instillation were noted. One case of rifampicin-induced toxidermia was recorded. CONCLUSION: IP urokinase and oral rifampicin in addition to conventional antibiotics resulted in a catheter salvage rate of 64% in persisting asymptomatic dialysate infection following a CoNS peritonitis. Larger studies are needed to confirm these results. In CoNS peritonitis, dialysate cultures should be repeated, even after clearing of the dialysate, to avoid missing persisting asymptomatic infection.