Biofilm formation in an experimental water distribution system: the contamination of non-touch sensor taps and the implication for healthcare

Abstract

Hospital tap water is a recognised source of Pseudomonas aeruginosa. UK guidance documents recommend measures to control/minimise the risk of P. aeruginosa in augmented care units but these are based on limited scientific evidence. An experimental water distribution system was designed to investigate colonisation of hospital tap components. P. aeruginosa was injected into 27 individual tap ‘assemblies’. Taps were subsequently flushed twice daily and contamination levels monitored over two years. Tap assemblies were systematically dismantled and assessed microbiologically and the effect of removing potentially contaminated components was determined. P. aeruginosa was repeatedly recovered from the tap water at levels above the augmented care alert level. The organism was recovered from all dismantled solenoid valves with colonisation of the ethylene propylene diene monomer (EPDM) diaphragm confirmed by microscopy. Removing the solenoid valves reduced P. aeruginosa counts in the water to below detectable levels. This effect was immediate and sustained, implicating the solenoid diaphragm as the primary contamination source.

Keywords:

• Pseudomonas aeruginosa
• tap water contamination
• non-touch sensor taps
• biofilm
• model water distribution system

Acknowledgements

The authors would like to thank Paul Day, Trevor Williams and Liam Oliver for their contribution to the design and build configuration of the EWDS; Dart Valley Systems for supplying the non-touch sensor taps and solenoids; Neoperl Ltd for supplying the outlet fittings; Howard Tolley for carrying out the scanning electron microscopy; Jane Turton for carrying out the VNTR analysis and Caroline Lymbery for additional technical assistance.

Conflict of interest disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was funded by the Department of Health. The views expressed in this publication are those of the authors and not necessarily those of PHE or any other Government Agency.