Recovery of bacteria from reprocessed high flux dialyzers after bacterial contamination of the header spaces and O-rings.

The Centers for Disease Control (CDC) have received reports of bacteremia in patients on high flux dialysis attributed to contamination of dialyzer header spaces or o-rings. A study was performed in which header spaces and o-rings of Hemoflow F-80 dialyzers (Fresenius AG, Bad Homburg, FRG) were exposed to an aqueous suspension of Xanthomonas maltophilia and Mycobacterium chelonae for 1 hour. After exposure, the dialyzers were reprocessed manually with 4% formaldehyde, 4% Renalin, 2.5% Renalin, or sterile water (SW) as a control, or with an automated reprocessing machine using 3.25% Renalin. After 48 hours the blood compartment (BC) was drained and rinsed twice with 500 ml of SW. Each BC sample was cultured. To simulate dialysis, separate circulates of SW were pumped through the DC and the BC. After 15 minutes, the BC circulate was cultured, headers were unscrewed, and o-rings, header caps, and fiber bundle ends were cultured. For each germicide, bacteria were recovered in low numbers, primarily from the o-rings and the o-ring groove in the header caps. In 38 tests, a total of 60 of 342 assays (17.5%) were positive. In only one of these tests one bacterial colony forming unit (cfu) was recovered from the BC circulate during simulated dialysis. It was concluded that if header spaces and o-rings are contaminated, bacteria could be sealed protectively from the germicide. However, concentrations of surviving bacteria were low, probably outside the BC, and did not effectively contaminate the BC circulate during simulated dialysis.