Extended water stagnation in buildings during the COVID-19 pandemic increases the risks posed by opportunistic pathogens

Legionella pneumophila response to shifts in biofilm structure mediated by hydrodynamics

Preventing legionellosis in water systems demands effective hydrodynamic management and biofilm mitigation. This study investigates the complex relationship between hydrodynamics (80 RPM and stagnation), biofilm mesoscale structure and Legionella pneumophila colonization, by addressing three key questions: (1) How do low flow vs stagnation conditions affect biofilm response to L. pneumophila colonization?, (2) How do biofilm structural variations mediate L. pneumophila migration across the biofilm?, and (3) Can specific hydrodynamic conditions trigger L. pneumophila entrance in a viable but nonculturable (VBNC) state? It was found that Pseudomonas fluorescens biofilms exhibit different responses to L. pneumophila based on the prevailing hydrodynamic conditions. While biofilm thickness and porosity decreased under shear (80 RPM), thickness tends to significantly increase when pre-established 80 RPM-grown biofilms are set to stagnation upon L. pneumophila spiking. Imposing stagnation after the spiking also seemed to accelerate Legionella migration towards the bottom of the biofilm. Water structures in the biofilm seem to be key to Legionella migration across the biofilm. Finally, shear conditions favoured the transition of L. pneumophila to VBNC states (∼94 %), despite the high viable cell counts (∼8 log10 CFU/cm2) found throughout the experiments. This research highlights the increased risk posed by biofilms and stagnation, emphasizing the importance of understanding the mechanisms that govern Legionella behaviour in diverse biofilm environments. These insights are crucial for developing more effective monitoring and prevention strategies in water systems.

Too much ado about data: continuous remote monitoring of water temperatures, circulation and throughput can assist in the reduction of hospital-associated waterborne infections

BACKGROUND

National and international guidance provides advice on maintenance and management of water systems in healthcare buildings; however, healthcare-associated waterborne infections (HAWIs) are increasing.

AIM

To identify parameters critical to water quality in healthcare buildings and to assess whether remote sensor monitoring can deliver safe water systems, thus reducing HAWIs.

METHODS

A narrative review was performed using the following search terms: (1) consistent water temperature AND waterborne pathogen control OR nosocomial infection; (2) water throughput AND waterborne pathogen control OR nosocomial infection; (3) remote monitoring of in-premises water systems AND continuous surveillance for temperature OR throughput OR flow OR use. Databases employed were PubMed, CDSR (Clinical Study Data Request) and DARE (Database of Abstracts of Reviews of Effects) from January 2013 to March 2024.

FINDINGS

Single ensuite-patient rooms, expansion of handwash basins, widespread glove use, alcohol gel and wipes have increased water system stagnancy resulting in amplification of waterborne pathogens and transmission risk of legionella, pseudomonas, and non-tuberculous mycobacteria. Manual monitoring does not represent temperatures across large complex water systems. This review deems that multiple-point continuous remote sensor monitoring is effective at identifying redundant and low use outlets, hydraulic imbalance and inconsistent temperature delivery across in-premises water systems.

CONCLUSION

As remote monitoring becomes more common there will be greater recognition of failures in temperature control, hydraulics, and balancing in water systems, and there remains much to learn as we adopt this developing technology within our hospitals.