Major Article| Volume 48, ISSUE 3, P304-308, March 2020

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Delftia acidovorans pseudo outbreak in portable reverse osmosis machines: Interventions to ensure safe and cost-effective hemodialysis

Published:January 14, 2020DOI:


      • Two-step filtration is an excellent method to improve water safety for hemodialysis and likely other departments.
      • Water-borne pathogens are likely to form a biofilm that is once formed, is extremely difficult to eradicate.
      • High volume membrane filtration is a more accurate way than direct culture to identify water pathogens.


      Reverse osmosis (RO), a major advance in hemodialysis (HD) safety, effectively clears most water organisms. Delftia acidovorans is an environmental water-borne pathogen that is rarely reported to cause human infections. We report a pseudo outbreak caused by colonization of RO machines with D acidovorans with no reported human infections and interventions to improve HD safety.


      Repeated positive RO product water cultures triggered our hospital to initiate an investigation, RO machines were examined for mechanical integrity by biomedical engineers. Cultures of product water as well as RO parts were done. Testing for bacterial relatedness after identification was performed. An investigation was conducted in a systematic fashion to determine the cause and the extent of the problem.


      Upon formal review of policies and procedures, there were minor deficiencies. Rectifying these deviations from policies did not stop the repeated positive water cultures. A 7-step investigation and correction was successfully conducted. City water testing with filtration and concentration methods was positive for D acidovorans. Major renovation of the HD unit with replacement of all RO machines and a 2-step water filtration resulted in elimination of the pseudo outbreak.


      City water was the source of biofilm formation of D acidovorans in RO machines that was not possible to eradicate. Application of incoming water filters was an effective preventive strategy. Replacement of RO machines after 4 failed disinfection attempts is the most cost-effective strategy as well for persistent positive water cultures. The HD remains RO water culture negative 2 years after changes.

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