AN OUTBREAK OF GRAM-NEGATIVE BACTEREMIA TRACED TO CONTAMINATED O-RINGS IN REPROCESSED DIALYZERS

Objective: To investigate an outbreak of gram-negative bacteremia in a n outpatient hemodialysis unit and to identify the source of contamina ting bacteria and the route by which bacteria gained access to the blo odstream. Design: A matched-pair, case-control study and a bacteriolog ic investigation of the hemodialysis unit and the implicated dialyzers . Setting: A university outpatient hemodialysis unit. Patients: Eleven patients receiving long-term hemodialysis who had a total of 12 episo des of primary gram-negative bacteremia and 12 matched controls. Measu rements: Clinical and demographic data were obtained for patients and controls. Dialysis unit procedures were observed for compliance with a septic technique. Cultures of potential environmental sources of bacte ria were obtained. Hemodialyzers from bacteremic and nonbacteremic pat ients were dismantled, and the component parts were cultured. Inoculat ion of O-rings (from Hemoflow F-80 dialyzer) with bacteria and simulat ed dialysis were done. Results: During January to October 1988, 12 epi sodes of primary gram-negative bacteremia caused by Pseudomonas cepaci a, Xanthomonas maltophilia, Citrobacter freundii, Acinetobacter calcoa ceticus var. anitratus, or Enterobacter cloacae occurred in 11 patient s. In 11 episodes, symptoms developed within 3 hours of starting hemod ialysis. Intravenous antibiotics were administered for 11 episodes, 3 episodes resulted in hospitalization, and all patients recovered. Case patients were more likely to have received high-flux dialysis with He moflow F-80 dialyzers (odds ratio congruent-to 11) than were controls. O-rings from dialyzers used by bacteremic patients were culture posit ive for the organism responsible for bacteremia. Three of the four dia lyzers were disinfected using the standard automated method and were r ecultured 72 hours later; the O-rings of all three dialyzers remained culture positive. Simulated dialysis using dialyzers with contaminated O-rings caused blood pathway contamination despite intervening reproc essing. When the disinfection method for F-80 dialyzers included remov al and complete disinfection of the O-rings, O-ring and blood pathway cultures were consistently negative. After this procedure was made rou tine, no episodes of primary gram-negative bacteremia occurred during the next 6 months. Conclusions: Because dialyzers with removable heade rs and O-rings are widely used in patients receiving long-term hemodia lysis, disinfection procedures should include measures to ensure adequ ate disinfection of O-rings.