What are non-tuberculous mycobacteria and what are the dangers?
Recognised as an ’emerging public health concern’, non-tuberculous mycobacteria (NTM) are posing an ever-increasing risk to immunocompromised populations. There has been a documented global increase in pulmonary NTM infections and disease, requiring an introspective analysis of existing water quality and safety measures.
In healthcare environments it is paramount to be informed on this growing threat, to protect those who are most at risk and to carry out the best possible care.
Non-tuberculous mycobacteria, also known as environmental mycobacteria, is a bacterium that can cause respiratory and healthcare-acquired infections (HCAIs). As with other opportunistic pathogens, including Legionella and Pseudomonas aeruginosa, the bacteria do not typically cause harm to the wider population.
However, for certain demographics, such as patients in augmented care settings, the risk of infection and subsequent severe illness (and even fatality) is significantly higher. It is particularly harmful for those with pre-existing lung conditions, a weakened immune system, autoimmune diseases or those taking immunosuppressive medications.
A persistent bacterium needs specialist attention
NTM naturally occur within water and form biofilm within water systems. Once formed, this biofilm can survive temperatures up to 50°C and current chemical shock treatments are ineffective in preventing colonisation, making the NTM bacteria very difficult to get rid of. Similar to Legionella, the bacteria colonise organic materials and natural plastics, with higher colonisation rates in shower hoses and EPDM (Ethylene Propylene Diene Monomer) flexible hoses compared to copper or glass. This tenacity means that additional measures are required to reduce the risk of infection when designing, constructing and operating augmented care facilities.
The NHS Technical Bulletin (NETB) No. 2024/3, published in August 2024, provides additional guidance over and above the existing advice outlined in the Health Technical Memorandum HTM 04-01, on how to manage the risks posed by waterborne pathogens such as Legionella and Pseudomonas.1,2
In augmented care facilities, any non-sterilised water poses a potential threat: water and ice used for drinking and food preparation; water used for personal hygiene, including toilet flushing; water used for cleaning; the entire water distribution system, its outlets and the drainage system; and, significantly for manufacturers, any fittings, components and equipment that have been tested with water prior to being installed.
In healthcare environments, it is the responsibility of the professionals and institutions to protect vulnerable individuals against HCAIs, which are, unfortunately, contracted by an estimated 300,000 patients in England annually.3 With NTM infections on the rise, it is imperative that action is taken before more immunocompromised individuals fall ill as a result.
This requires an awareness at all levels to understand the transmission pathways and minimise the risk. This translates specifically to the facility design stage, the specification and installation of fixtures and fittings, and the day-to-day operation of augmented care facilities.
For all new augmented care units, the NETB No. 2024/3 is clear that the design stage is fundamental to eliminating the risk of infection. For existing facilities, the Water Safety Group and Infection Prevention and Control teams must identify the risk level and put in appropriate measures to eradicate the risk where possible, or control it if not. The resulting plan should include multiple barriers to provide a failsafe, should one method of infection prevention fail.
Devising a solution
At the heart of the guidance is the possibility of removing all non-sterile water from high-risk patient areas. It asks the question: Are water outlets necessary in high-risk patient areas? For some very vulnerable patients, the risk of exposure to non-sterile water, and the associated risk of contracting a life-threatening infection, is too high. As with Legionella and Pseudomonas, a risk-assessment is required to verify this need.
Some areas, such as post-operative areas for organ transplant patients, will emphatically not require non-sterile water. In these areas, wash-hand basins should not be located in the patient’s room. Washing stations and clinical sinks should be positioned outside patient bedrooms, either in an ensuite facility or in the lobby. Since NTM infections are typically caused by inhaling the bacteria in microdroplets, this will prevent exposure to sprays and aerosols.
However, for patients further down the recovery route, where the risk assessment deems it safe, a wash-hand basin may be installed. Here the guidance recommends avoiding exposure to waterborne pathogens by fitting a mixer tap that can be removed for disinfection purposes, and also fitting a sterilising-grade point-of-use (POU) filter. The design of the basin must minimise splashing and the outlet must not be directly over the drain to avoid retro-contamination. Patient’s personal items, including the bed, must be located at least two metres away from any sink, basin or shower to minimise the risk of splashing. Where necessary, effective splash screens should also be installed.
Complying with guidance during
the specification stage
At the specification stage, NETB No. 2024/3 requires that any equipment, components and fittings used for the delivery and drainage of water must not have an adverse effect on the microbiological or chemical quality of water, both at the point of installation and over time. Manufactured items can no longer be wet-tested or pressure-tested using water prior to installation in their final location, whether this testing takes place at the manufacturing site, or at a test bench in the care facility itself.
The guidance also states clearly that there must be no compromise to patient safety. Any potential conflict between Net Zero carbon sustainability targets and safe water management must always consider the patient risk. However, in augmented care facilities, NETB No. 2024/3 suggests that specifying a stand-alone hot water distribution, with an independent supply, local hot water production and shorter pipe runs, can have a two-fold benefit. A dedicated unit in augmented care facilities allows greater control of the water temperature within the system; it simplifies capacity planning so water circulation is guaranteed and dead-legs are avoided; and it prevents over consumption of water and energy.
Once installed, facilities teams must ensure adequate water quality throughout the delivery and drainage system, including verifying that the control measures are effective. This involves monitoring the water quality; ensuring components, equipment and fittings comply with Water Regulations; and that water temperatures are maintained. The guidance stipulates hot water must be distributed to arrive at the outlet at a temperature of 55°C within seconds (ideally well within 15 seconds). Cold water temperature must be maintained below 20°C. If cold water temperature is likely to rise above 18°C, potentially during an exceptionally warm spring or in later summer, then facilities should consider cooling mechanisms.
Existing buildings’ schematics must be updated, factoring in any changes of use to remove dead-legs or areas of stagnation. If wash-hand basins or showers are moth-balled, the pipe run must be closed off to avoid any stagnation, especially since underutilised outlets can also have an impact on line temperature and biocide efficiency. Where there is any doubt about the efficacy of thermal and chemical treatment, the guidance states that a correctly fitted sterilising-grade POU filter will act as an additional barrier for both tap and shower outlets.
Point of use filters — a convenient solution
Studies have shown that POU filtration can significantly reduce NTM counts at the outlet, protecting professionals and patients alike.4 However, in augmented care settings, NETB No. 2024/3 sets out certain criteria. The filter, with a sterilising-grade 0.2 µm absolute-rated, must be effective for its stated lifespan, considering the specific water charge, usage patterns, water pressure and system temperatures. It must be robust, with a no-leak connection (air-pressure tested). There must be sufficient activity space beneath a POU fitted to a mixer tap to allow for its intended use; to avoid surface contact with the filter, tap and basin; and to prevent any retro-contamination from splashing.
Filter technology has advanced, even over the past 10 years. Compact point-of-use filters are a simple and convenient way to ensure patient safety even for the most vulnerable groups. Microfiltration targets these pathogenic bacteria and physically separates elements between 0.1 and 10 micrometres in the water by passing it through filter membranes. Point-of-use filters are typically rated to 0.2 µm, removing suspended matter and bacteria as well as minerals, fungi and mycobacteria (such as NTM).
Tubular membrane microfiltration and its unique benefits
The two types of membranes currently used in point-of-use filters are pleated membranes or tubular membranes. In the medical world, tubular membrane microfiltration is commonly used to eliminate water contamination at the point of use as it is an effective means of protecting patients and residents against waterborne pathogens. Second-generation tubular membrane filters, made from several porous tubes arranged parallel to one other, provide a larger exchange surface and, therefore, result in a higher flow rate at the outlet.
There are numerous other benefits to tubular membrane microfiltration compared to other filtration methods. Firstly, it is very reliable, eliminating all bacteria and other waterborne microorganisms (with the exception of viruses). Their reliability is guaranteed by the standard ASTM F 838-20 which assesses the membrane’s ability to retain Brevundimonas diminuta, the smallest known bacterial species which measures 0.3 µm. Secondly, the hollow fibre membrane is very compact, allowing low-volume devices to contain a large filtration surface area. Finally, they have a good tolerance to clogging as suspended matter remains on the surface of the tubular membrane, extending the filters lifespan.
The technology behind the solution
Hollow-fibre technology delivers a compact, effective filtration device. The point-of-use filter is made up of a collection of polyethylene hollow fibres grouped together into a unit. These fibres are extremely fine and flexible, with an exterior diameter of 0.6mm and a thickness of several tens of microns.
The fibres are hollow and shaped like a straw or tube. The hollow fibre membranes have multiple pores which vary in size from 0.01 – 0.1 micron. Each membrane consists of several surfaces with microporous structures (micro slits). Bacteria and any particles in suspension that are larger than 0.1µm are trapped by these structures and retained permanently on the external surface of the membrane.
The water requiring treatment flows at right angles to the filter surface and passes through the membrane due to the pressure difference on either side of the membrane, causing the water to flow from the external to the internal surface of the fibre.
Bacteria and other microparticles that cannot pass through the gaps in the membrane structure are retained on the outer surface and therefore do not penetrate the membrane. The filters’ hollow-fibre filtration area makes it possible to filter a larger volume of water. Consequently, the storage capacity for bacteria and impurities trapped inside the filter is much greater.
In the face of this growing threat to patient health, it is imperative that healthcare facilities take initiative to protect the most vulnerable. Aquatools point-of-use filters offer 1, 2, 3 and 4 month point-of-use filters for taps and showers. Their tubular membrane microfiltration technology offers protection for users, and peace of mind for facilities managers.
References
1 NHS Estates Technical Bulletin (NETB) No.2024/3, doi. 27 August 2024.
2 Health Technical Memorandum 04-01: Safe water in healthcare premises. First published May 2016.
3 NICE. (2024). Healthcare-associated infections: prevention and control in primary and community care. https://tinyurl.com/ycy54a99.
4 Norton G. J., Williams M., Falkinham J. O., 3rd, & Honda J. R. (2020). Physical Measures to Reduce Exposure to Tap Water-Associated Nontuberculous Mycobacteria. Front Public Health, 8, 190. doi:10.3389.