Investigating alternative materials to EPDM for automatic taps in the context of Pseudomonas aeruginosa and biofilm control

Hutchins C. (2020)

Journal of Hospital Infection

Background

Automatic taps use solenoid valves (SVs) which incorporate a rubber (typically EPDM) diaphragm to control water flow. Contaminated SVs can be reservoirs of opportunistic pathogens such as Pseudomonas aeruginosa; an important cause of healthcare-associated infection.

Aims

To investigate the attachment and biofilm formation of P. aeruginosa on EPDM and relevant alternative rubbers to assess the impact on water hygiene in a laboratory model.

Methods

Biofilm formation on EPDM, silicone and nitrile rubber coupons was investigated using a CDC biofilm reactor. SVs incorporating EPDM or nitrile rubber diaphragms were installed onto an experimental water distribution system (EWDS) and inoculated with P. aeruginosa. P. aeruginosa water levels were monitored for 12-weeks. SVs incorporating diaphragms (EPDM, silicone or silver ion-impregnated silicone rubber), pre-colonised with P. aeruginosa, were installed and the effect of flushing as a control measure was investigated. The concentration of P. aeruginosa in the water was assessed by culture and biofilm assessed by culture and microscopy.

Findings

Bacterial attachment was significantly higher on nitrile (6.2x105 CFU/coupon) and silicone (5.4x105 CFU/coupon) rubber than on EPDM (2.9x105 CFU/coupon)(p<0.05, n=17). Results obtained in vitro did not translate to the EWDS where, after 12-weeks in situ, there was no significant difference in P. aeruginosa water levels or biofilm levels. Flushing caused a superficial reduction in bacterial counts after <5-minutes stagnation.

Conclusion

This study did not provide evidence to support replacement of EPDM with (currently available) alternative rubbers and indicated the first sample of water dispensed from a tap should be avoided for use in healthcare settings.

Journal of Hospital Infection

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