Safety and cleaning of medical materials and devices

A study was undertaken to evaluate different procedures to safely remove mi croorganisms, protein, and mammalian cells from materials and provide a sui table method for cleaning and assessing effectiveness of cleaning medical d evices for reuse or for analysis of failure. Safety considerations for the personnel performing the cleaning or handling the device after cleaning are important issues, Polystyrene plates (96 well) were used to simulate devic e surfaces not amenable to manual scrubbing, Staphylococcus epidermidis, Ca ndida albicans, Escherichia coli, Pseudomonas aeruginosa and oral flora wer e grown in the plates. The plates were stained with crystal violet and the optical densities recorded. The results indicated that E. coli did not adhe re well and Pseudomonas formed clumps that mere easily detached from the su rface of the plates. However, S. epi, C. albicans, and the oral organisms f ormed adherent biofilms that were difficult to remove from the plates, Dete rgents with enzymes and sodium hypochlorite (NaOCl) bleach mere both effect ive in removing the biofilm, Other detergents and surfactants were not effe ctive. The aldehyde agents did not remove the organisms and made further cl eaning difficult. Allowing the biofilm to dry first made cleaning very diff icult, Only the NaOCl bleach could subsequently remove the dried or aldehyd e fixed organisms from the wells. The same 96-well polystyrene plate format was used to measure the amount of protein and cell adherence as well as th e effectiveness of subsequent cleaning. Bradford reagent was used to detect protein as a measure of the cleaning efficacy. As with the bacteria, NaOCl bleach was effective at removing the protein and cells that had been dried or fixed by formalin or alcohol, whereas detergent with enzymes was not ve ry effective. This study confirmed that used medical devices, contaminated with microorganisms, protein, and/or mammalian cells, should not be allowed to dry before cleaning and that a thorough cleaning procedure should prece de sterilization or disinfection (with the exception of NaOCl bleach which also cleans). (C) 2000 John Wiley & Sons, Inc.