Jp. Flaherty et al., AN OUTBREAK OF GRAM-NEGATIVE BACTEREMIA TRACED TO CONTAMINATED O-RINGS IN REPROCESSED DIALYZERS, Annals of internal medicine, 119(11), 1993, pp. 1072-1078
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.