Point-of-use filters to prevent fungal contamination of hospital water

Abstract number: P1110

Onken A., Gaustad P., Abrahamsen T.G., Warris A.

Objectives: To investigate whether the installation of point-of-use filters could retain the fungal contamination of the hospital water at the Rikshospitalet, Univ. of Oslo, Norway. Previously, we showed that the hospital water of the paediatric oncology department was contaminated by fungal organisms. Furthermore, hospital water has been suggested as a route for transmission of invasive filamentous fungal infection and preventive measures are needed to protect immunocompromised patients.

Methods: In April 2005 water samples were taken from 10 showers (hot water) and 10 sink taps (cold water) at the paediatric oncology ward, including four BMT units. The samples were collected in sterile glass bottles on three different days in an 8-day period. Then, point-of-use filters (Pall-Corporation^®) were installed on the taps and showerheads. Sixty samples were taken from showers and sink taps before installation point-of-use filters, 20 samples were taken with the filters in place. The collected samples were filtered through sterile filters, pore size 0.45 mm. The filters were deposited on Sabouraud glucose agar, incubated for 7 days and examined for fungal species and identified by macroscopic and microscopic characteristics. Aspergillus isolates were identified to the species level.

Results: Filamentous fungi were recovered from 97% (58 of 60 samples) of the water samples before installation of the point-of-use filters. Aspergillus fumigatus was isolated in 21 of 60 samples (35%).

On average, 2.9 colony forming units (cfu)/ 500 ml of filamentous fungi were recovered, Aspergillus sp. 0.7 cfu/ 500 ml, A. fumigatus 0.6 cfu/ 500 ml.

After the installation of local filters no moulds were recovered (20 samples), but the filters were rapidly occluded within 1 or 2 days. Electron microscopy showed that the surface of the occluded filters was completely covered with large amounts of particulate colloidal material.

Conclusions: The installation of point-of-use filters retained the fungal contamination of the hospital water completely. Due to a high level of organic material in the water, the filters were blocked after being in use for only 1 or 2 days. Pre-filtration at the inlet of the water into the paediatric oncology department should be carried out to get rid of the organic materials. At present, it is not clear, if this is feasible. Our findings indicate that point-of-use filters might be useful unless the water contains much organic material blocking the filters.