Investigating engineering and human behavioural factors influencing the colonisation of hospital taps with Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa is an important nosocomial pathogen and its contamination of hospital water poses a threat to immunocompromised patients and is frequently associated with colonised taps. Engineering and human behavioural factors are reported to play a role in tap contamination. Conventional plumbing components and novel alternatives were investigated to determine the role that materials and designs play on P. aeruginosa survival and persistence in vitro (bioreactor model) and in situ (experimental water distribution system (EWDS)). A questionnaire was developed to explore the knowledge, attitudes and beliefs/opinions of hospital staff surrounding water hygiene and their role in maintaining it. A cloth contamination model was developed to investigate behaviour-derived contamination of taps.
Antimicrobial effects were only evident on copper-based materials in vitro (3.1x101-1.7x102 CFU/material coupon; significantly reduced planktonic survival compared to non-antimicrobial controls (>6-log (10) reduction (p<0.05)); no antimicrobial effects were observed on silver- impregnated material (1.5x105 CFU/material coupon; planktonic reduction of <1.3-log (10) (p>0.05)). Within the EWDS, no significant differences in water- or biofilm-contamination levels were observed between solenoid valves (SVs) using nitrile rubber diaphragms compared to conventional EPDM. Silicone SVs also supported P. aeruginosa biofilm and some SVs arrived pre-contaminated with P. aeruginosa. Evidence was provided for taps to be flushed pre-use. The cloth-contamination model demonstrated that whilst all outlet fittings (OFs) tested could become contaminated with P. aeruginosa, alternative OFs were more effective at reducing contamination over a series of flushes. No significant difference in P. aeruginosa survival over 24-hours was observed between conventional OFs (4.4-log (10) reduction) and alternatives (3.5-5.2-log (10) reductions). Only 59% of staff surveyed believed that tap water could act as a vector for infection. Staff responses demonstrated varying knowledge of water hygiene, but a willingness to changepractices. A standardised, staff-wide water hygiene training programme should be developed. Best practice should, in-turn, allow for effective engineering solutions to reduce P. aeruginosa contamination unhindered.

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ORCID for Jeremy Webb: orcid.org/0000-0003-2068-8589

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