title: Hygienic safety of reusable tap water filters (Germlyser) with an operating time of 4 or 8 weeks in a haematological oncology transplantation unit.
abstract: BACKGROUND
  Microbial safe tap water is crucial for the safety of immunosuppressed patients.
  
  
  METHODS
  To evaluate the suitability of new, reusable point-of-use filters (Germlyser, Aquafree GmbH, Hamburg, Germany), three variations of a reusable filter with the same filter principle but with different outlets (with and without silver) and inner surface coating of the filter encasements (with and without nano-crystalline silver) were tested. The filter efficacy was monitored over 1, 4 and 8 weeks operating time in a haematological oncology transplantation unit equipped with 18 water outlets (12 taps, 6 showers).
  
  
  RESULTS
  The filtered water fulfilled the requirements of absence of pathogens over time. From 348 samples, 8 samples (2.3%) exceeded 100 cfu/ml (no sample > or = 500 cfu/ml). As no reprocessed filter exhibited 100% filter efficacy in the final quality control after each reprocessing, these contaminations could be explained by retrograde contamination during use.
  
  
  CONCLUSIONS
  As a consequence of the study, the manufacturer recommends changing filters after 4 weeks in high risk areas and after 8 weeks in moderate infectious risk areas, together with routine weekly alcohol-based surface disinfection and additionally in case of visible contamination. The filter efficacy of the 3 filters types did not differ significantly regarding total bacterial counts. Manual reprocessing proved to be insufficient. Using a validated reprocessing in a washer/disinfector with alkaline, acid treatment and thermic disinfection, the filters were effectively reprocessable and now provide tap water meeting the German drinking water regulations as well as the WHO guidelines, including absence of pathogens.
authors.affiliation: Institute for Hygiene and Environmental Medicine, Germany. daeschlein@uni-greifswald.de <daeschlein@uni-greifswald.de>
authors.forename: Georg
authors.initials: G
authors.lastname: Daeschlein
authors.forename: William H
authors.initials: WH
authors.lastname: Krüger
authors.forename: Christian
authors.initials: C
authors.lastname: Selepko
authors.forename: Markus
authors.initials: M
authors.lastname: Rochow
authors.forename: Gottfried
authors.initials: G
authors.lastname: Dölken
authors.forename: Axel
authors.initials: A
authors.lastname: Kramer
mesh_terms: D015169:Colony Count, Microbial; D004203:Disinfection / Q000295:instrumentation / Q000379:methods / Q000592:standards; D017743:Equipment Reuse; D005374:Filtration / Q000295:instrumentation / Q000379:methods / Q000592:standards; D005858:Germany; D019337:Hematologic Neoplasms; D006757:Hospital Units; D006801:Humans; D007875:Legionella / Q000302:isolation & purification; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification; D014180:Transplantation / Q000592:standards*; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*; D014881:Water Supply / Q000592:standards*