title: An outbreak of gram-negative bacteremia in hemodialysis patients traced to hemodialysis machine waste drain ports.
abstract: OBJECTIVE
  To investigate an outbreak of gram-negative bacteremias at a hemodialysis center (December 1, 1996-January 31, 1997).
  
  
  METHODS
  Retrospective cohort study. Reviewed infection control practices and maintenance and disinfection procedures for the water system and dialysis machines. Performed cultures of the water and dialysis machines, including the waste-handling option (WHO), a drain port designed to dispose of saline used to flush the dialyzer before patient use. Compared isolates by pulsed-field gel electrophoresis.
  
  
  METHODS
  A hemodialysis center in Maryland.
  
  
  RESULTS
  94 patients received dialysis on 27 machines; 10 (11%) of the patients had gram-negative bacteremias. Pathogens causing these infections were Enterobacter cloacae (n = 6), Pseudomonas aeruginosa (n = 4), and Escherichia coli (n = 2); two patients had polymicrobial bacteremia. Factors associated with development of gram-negative bacteremias were receiving dialysis via a central venous catheter (CVC) rather than via an arterio-venous shunt (all 10 infected patients had CVCs compared to 31 of 84 uninfected patients, relative risk [RR] undefined; P<.001) or dialysis on any of three particular dialysis machines (7 of 10 infected patients were exposed to the three machines compared to 20 of 84 uninfected patients, RR = 5.8; P = .005). E cloacae, P aeruginosa, or both organisms were grown from cultures obtained from several dialysis machines. WHO valves, which prevent backflow from the drain to dialysis bloodlines, were faulty in 8 (31%) of 26 machines, including 2 of 3 machines epidemiologically linked to case-patients. Pulsed-field gel electrophoresis patterns of available dialysis machine and patient E cloacae isolates were identical.
  
  
  CONCLUSIONS
  Our study suggests that WHO ports with incompetent valves and resultant backflow were a source of cross-contamination of dialysis bloodlines and patients' CVCs. Replacement of faulty WHO valves and enhanced disinfection of dialysis machines terminated the outbreak.
authors.affiliation: Hospital Infections Program, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Wang
authors.forename: R B
authors.initials: RB
authors.lastname: Levine
authors.forename: L A
authors.initials: LA
authors.lastname: Carson
authors.forename: M J
authors.initials: MJ
authors.lastname: Arduino
authors.forename: T
authors.initials: T
authors.lastname: Killar
authors.forename: F G
authors.initials: FG
authors.lastname: Grillo
authors.forename: M L
authors.initials: ML
authors.lastname: Pearson
authors.forename: W R
authors.initials: WR
authors.lastname: Jarvis
mesh_terms: D000554:Ambulatory Care Facilities; D015331:Cohort Studies; D003428:Cross Infection / Q000453:epidemiology / Q000209:etiology*; D004196:Disease Outbreaks; D004868:Equipment Failure; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D008396:Maryland / Q000453:epidemiology; D006435:Renal Dialysis / Q000009:adverse effects* / Q000295:instrumentation; D012189:Retrospective Studies; D012307:Risk Factors