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Open Access Research article

Hygienic safety of reusable tap water filters (Germlyser®) with an operating time of 4 or 8 weeks in a haematological oncology transplantation unit

Georg Daeschlein1, William H Krüger2*, Christian Selepko1, Markus Rochow1, Gottfried Dölken2 and Axel Kramer1

Author affiliations

1 Institute for Hygiene and Environmental Medicine, Germany

2 Dept. of Internal Medicine C – Haematology and Oncology, Stem Cell Transplantation, Ernst Moritz Arndt University, Greifswald, Germany

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Citation and License

BMC Infectious Diseases 2007, 7:45  doi:10.1186/1471-2334-7-45

Published: 23 May 2007

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 ≥ 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.

Conclusion

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.