Faucet aerator design influences aerosol size distribution and microbial contamination level

Drinking water plumbing systems are a hot spot for antimicrobial-resistant pathogens

BACKGROUND

Antimicrobial-resistant (AMR) pathogens in drinking water plumbing systems represent a significant yet underestimated public health threat.

METHODS

This is the first study to use qPCR and culture-based methods to investigate the prevalence of key AMR threats, meticillin resistant Staphylococcus aureus (MRSA) and carbapenem resistant Pseudomonas aeruginosa and Acinetobacter baumannii, in Australian hospital and residential drinking water and biofilm samples.

FINDINGS

Seventy-three per cent of residential water and biofilm samples were qPCR positive for at least one target pathogen compared with 38% of hospital samples, and 45% of residential plumbing fixtures harboured at least two target pathogens. Thirty-seven per cent of water and biofilm samples were qPCR positive for P. aeruginosa, 22.3% for A. baumannii and 21.7% for S. aureus. Using culture, 10% of samples were positive for P. aeruginosa, 8% for A. baumannii and 7% for S. aureus. Of these, 29% of P. aeruginosa and 28% of A. baumannii culture isolates were carbapenem resistant, and 54% of S. aureus isolates were identified as MRSA. Drain biofilms were the most common reservoir for AMR A. baumannii, S. aureus and P. aeruginosa. Carbapenem resistance genes including blaNDM-1, blaOXA-48, blaKPC-2 and blaVIM were found in biofilm samples otherwise negative for P. aeruginosa, indicating plumbing biofilms may act as eDNA reservoirs.

CONCLUSIONS

These findings underscore the critical role of plumbing biofilms as hotspots for diverse AMR pathogens, amplifying risks for vulnerable populations, particularly in home healthcare settings. This study highlights an urgent need for enhanced surveillance and targeted interventions to mitigate AMR risks in drinking water plumbing systems.

Disinfection of sink drains to reduce a source of three opportunistic pathogens, during Serratia marcescens clusters in a neonatal intensive care unit

OBJECTIVE

Evaluate the effects of five disinfection methods on bacterial concentrations in hospital sink drains, focusing on three opportunistic pathogens (OPs): Serratia marcescens, Pseudomonas aeruginosa and Stenotrophomonas maltophilia.

DESIGN

Over two years, three sampling campaigns were conducted in a neonatal intensive care unit (NICU). Samples from 19 sink drains were taken at three time points: before, during, and after disinfection. Bacterial concentration was measured using culture-based and flow cytometry methods. High-throughput short sequence typing was performed to identify the three OPs and assess S. marcescens persistence after disinfection at the genotypic level.

SETTING

This study was conducted in a pediatric hospitals NICU in Montréal, Canada, which is divided in an intensive and intermediate care side, with individual rooms equipped with a sink.

INTERVENTIONS

Five treatments were compared: self-disinfecting drains, chlorine disinfection, boiling water disinfection, hot tap water flushing, and steam disinfection.

RESULTS

This study highlights significant differences in the effectiveness of disinfection methods. Chlorine treatment proved ineffective in reducing bacterial concentration, including the three OPs. In contrast, all other drain interventions resulted in an immediate reduction in culturable bacteria (4-8 log) and intact cells (2-3 log). Thermal methods, particularly boiling water and steam treatments, exhibited superior effectiveness in reducing bacterial loads, including OPs. However, in drains with well-established bacterial biofilms, clonal strains of S. marcescens recolonized the drains after heat treatments.

CONCLUSIONS

Our study supports thermal disinfection (>80°C) for pathogen reduction in drains but highlights the need for additional trials and the implementation of specific measures to limit biofilm formation.

Characterization of the aerosol produced from an aerated jet

Faucet aerators that form aerated water jets generate aerosols, which can constitute a risk of infection if the water is contaminated, particularly for vulnerable individuals near the sink. In this study, we characterize the size and trajectory of water droplets produced from an aerated jet. The detected particle diameter ranged from 3 to 150μm. The concentration of droplets in the air varied from near-zero to a maximum of 2×10¹¹particles/m³, depending on the location relative to the jet. We found four relevant categories of droplets based on their trajectories following their emission at the jet's free surface: particles with inertia high enough to escape the immediate vicinity of the jet (category 1), particles moving towards the jet (category 2), particles drawn into the aerator, which only included particles with a diameter smaller than 50μm (category 3), and particles with a near-vertical trajectory (category 4). Tracing category 1 particles to their generation location on the water interface shows a higher emission rate near the aerator. Finally, we employ a numerical model to compute the subsequent trajectories of droplets detected at the limits of the sampled domain. We find that particles whose diameter is smaller than 55μm completely dry and become airborne. Larger droplets deposit within a radius of 7cm around the jet, assuming a surface is located 20cm below the aerator tip. These results increase the fundamental understanding of the emission mechanisms of droplets in aerated jets and their fate in the sink environment.

What is the risk of acquiring SARS-CoV-2 from the use of public toilets?

Public toilets and bathrooms may act as a contact hub point where community transmission of SARS-CoV-2 occurs between users. The mechanism of spread would arise through three mechanisms: inhalation of faecal and/or urinary aerosol from an individual shedding SARS-CoV-2; airborne transmission of respiratory aerosols between users face-to-face or during short periods after use; or from fomite transmission via frequent touch sites such as door handles, sink taps, lota or toilet roll dispenser. In this respect toilets could present a risk comparable with other high throughput enclosed spaces such as public transport and food retail outlets. They are often compact, inadequately ventilated, heavily used and subject to maintenance and cleaning issues. Factors such as these would compound the risks generated by toilet users incubating or symptomatic with SARS-CoV-2. Furthermore, toilets are important public infrastructure since they are vital for the maintenance of accessible, sustainable and comfortable urban spaces. Given the lack of studies on transmission through use of public toilets, comprehensive risk assessment relies upon the compilation of evidence gathered from parallel studies, including work performed in hospitals and prior work on related viruses. This narrative review examines the evidence suggestive of transmission risk through use of public toilets and concludes that such a risk cannot be lightly disregarded. A range of mitigating actions are suggested for both users of public toilets and those that are responsible for their design, maintenance and management.