An in VITRO Test of the Efficacy of the Perioexr CAPD Filterset

In an attempt to reduce the incidence of peritonitis caused by contamination during CAPD bag change procedures, Millipore (Bedford, Mass) developed the Peridex R CAPD filterset. Using the bacterium Serratia marcescens as the challenge organism, this filterset has been evaluated in vitro during 30 days of mock CAPD conducted in our laboratory. S. marcescens was chosen because it has been shown to remain viable in peritoneal dialysis (PD) fluid for more than 30 days. During the test period, the membrane filter and bypass lines were separated to allow identification of the route of bacterial invasion; in essence, two artificial peritoneal cavities were created. The membrane filter, composed of 0.22 [IJ.]m cellulose ester, maintained sterility of the filtered dialysate (n = 5) during the test period. However, the one-way bypass valve had a 60% failure rate by day 18, allowing the test organism to enter the other peritoneal cavity. Under the conditions of this study, the CAPD filterset was shown to be bacteriologically safe for up to 17 days, since contamination was detected following the 18th overnight dwell. Therefore we recommend that filtersets be changed twice monthly to prevent peritonitis due to touch contamination, resulting from failure of the one-way bypass valve on the dialysate outflow line.