I have been a Consultant Microbiologist at Great Ormond Street Hospital for the past 20 years; my work focuses on the prevention, diagnosis, and treatment of hospital infection. While I have no formal training in engineering, I’m the named inventor on three patents — including, most recently, the Tuba Drain. During my time at GOSH I have been alarmed by the growing number of patients admitted carrying highly antibiotic-resistant bacteria, and with infections by such bacteria. Now, each month, I’m noticing that the number seems to be higher than in the previous one.
The development of the Tuba Drain resulted from me looking at a window in my office door that looks onto a sink with a visible trap. This led me to think of how upwards splash could prevented by the insertion of a bent tube into the system. The Tuba Drain (TD) is a component for a sink drain that prevents resistant bacteria ascending into sinks and hence transferring to staff and patients, so has the potential to help reverse the rise in antibiotic-resistant bacteria.
Exponential rises
Despite international concern about antimicrobial resistance, efforts to control the immediate problem of rapid and increasing spread of resistance have been lacking. Ever since COVID, the term ‘exponential rise’ has widely been wrongly used. The true meaning is illustrated by the following story:
There is a legend that a man asked a king to be paid for his services in rice. On day 1 he would have one grain of rice placed on a square on a chessboard, on the second day two grains on the second square, and for the following 62 days on each day he would have double the amount of the previous day. The king suggested that this was too little. The total was more rice than there was in the world.
The number of hospital patients in England and Wales carrying in their guts multi-resistant bacteria has been rising at an ever-increasing rate (possibly exponential) — see the graph in Figure 1 for a related measure. The data ends in 2016, since at that point there became too many to measure. There is no reason to suppose that this possibly exponential rise has ceased since. That gives some idea of where we are headed unless major efforts are made now.
The carriage of resistance is now beginning to translate into deaths in the UK, and has been for some time elsewhere. This is why the lethargy about transmission is beginning to be replaced by concern. (Better very late than never!) At a time when many new hospitals are being built in the UK, there is now a widespread view that more account needs to be taken of infection control needs when designing new hospitals. This has led to the creation of the Built Environment Infection Prevention Initiative by the Healthcare Infection Society, and the release of its The Silent Pandemic report,1 which demands urgent action. Key recommendations include involving IPC professionals from the earliest stages of design and planning, introducing mandatory IPC training across disciplines, and standardising best-practice design frameworks for infection prevention.
Efforts needed urgently
Efforts that are needed urgently are approaches to decolonise patients, but also — importantly — efforts to stop bacteria carried in sink drains from ascending into sinks and so onto the hands of staff, who then transmit them to patients. Many hospital outbreaks of near-untreatable infection have been caused by the ascent of multi-resistant bacteria from drains into sinks.2 The concern is now so great that desperate hospitals are resorting to removing, and not replacing, sinks in their intensive care units. This makes it impossible for staff to wash their hands close to where they are working. Not all sinks can be removed, so safer sinks are needed.
The usual approach to hospital sink drainage is obviously flawed. Water exiting the sink falls from a height directly into a pool of contaminated water in the U-bend or trap, causing contaminated splashes to contaminate the sink outlet.3 Some sinks even have taps which direct a jet of water directly into the plughole, which is extremely bad design.
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Tuba Drain
A simple solution to the problem is the Tuba Drain.4 This is simply a bent length of pipe made of an antimicrobial material that descends throughout its length. The inlet of the Tuba Drain includes a slope of changing gradient (the ski-jump slope) that redirects the water with minimum splashing. Any splashing that does occur is not from a pool of contaminated water, as there is no pool where the water is landing. While the Tuba Drain is designed to fully drain, and therefore dry (drying kills many of the key bacteria), and is also made of antibacterial copper, it would be possible for a layer of bacteria to grow on its surface. In that event it would be possible to kill the bacteria simply by heating the Tuba Drain in situ using an electric heat gun of the sort used for stripping paint. In very high risk areas this could be a regular treatment of Tuba Drains. Copper is a good conductor, and is heat-resistant, and the length of the TD ensures that its ends could be not so hot as to damage plastic connected to them.
Lab and hospital testing
The TD has been demonstrated to be effective both in the laboratory and in a hospital Outpatients’ Department. A laboratory assessment was made of the TD using drain components that were not attached to a sink, to investigate whether it prevented splashes from reaching a point just downstream of the sink outlet.
A 35 mm diameter brass compression fitting was attached to the top of a brass bottle trap; then 3.5 ml of a broth culture of bacteria was added to the bottle trap through its outlet. A 60 mm long 35 mm outer diameter sterile copper tube was then attached to the compression fitting. The non-draining part of the trap was filled with water from its inlet. After filling the trap a cold tap was then run full on for 10 seconds into the top of the copper pipe. The luminal surface was swabbed to sample any bacteria present. The pipe was disconnected, and culture added, after which the TD was attached to the compression fitting. The tap was run as above into the top of the TD. The internal lumen of the top of the TD was swabbed to a depth of 10 cms (the free length of the swab) to sample any bacteria present.
The process above was then repeated a further 7 times. 8/8 swabs from the 60 mm pipes and 0/8 of those from the TD grew the strain of bacteria that had been added to the traps p=0.002.
The result of this study was as expected. Bacteria splashed upwards with normal plumbing, but the Tuba Drain prevented this from happening in all cases.
While this is an obvious advantage, we also tested the function of the Tuba Drain in an Outpatients’ Department in a blinded, randomised trial. Bacteria that are associated with clinical infection and antibiotic resistance were the organisms of primary interest, and termed ‘target bacteria’. Those were the bacteria that we decided to study, before the start of the trial. Sinks were paired into those that we judged would have a similar risk of colonisation by the resistant bacteria we were studying. This related primarily to the type of use of the sinks. Each member of each pair was randomised to receive either new, standard plumbing up to and including the trap (18 sinks), or the same new standard plumbing, but including the TD inserted between the sink outlet and trap.
Counts of target bacteria in swabs from the sink outlets were determined blindly before and monthly after the plumbing change for a year. The TDs fitted into the required spaces, and functioned without problems. The geometric means (over months) of the counts of target bacteria in TD-plumbed sinks was lower than those in their paired controls p= 0.012. The Tuba Drains remained in Outpatients’ for a further year, and during the two years of their use there were no problems, and no maintenance needed.
Preventing the ascent of splashes
The TD prevents the ascent of splashes from the trap, including those containing antibiotic-resistant bacteria. The design slopes downwards throughout its course, which facilitates drying when not in use. As the Gram-negative bacteria that colonise traps are killed by drying, this is a helpful feature for preventing the formation of surface films of bacteria (biofilms), as is the use of antimicrobial copper.
The sinks used were Ideal Standard Contour sinks fitted with a wide flexible waste pipe which included a 90-degree bend and incorporated an antimicrobial substance. TDs could be fitted to other types of sinks, provided there was space for them, and enough vertical drop between the sink outlet and the waste pipe to which the trap is joined. The TDs tested in the above studies were made up from bought-in bends that were joined together. A more cost-effective approach would be to bend the Tuba Drains out of copper tube. Most bending machines are not able to do that in a single part, so the plan is to make two parts and solder them together inside an external sleeve in the middle of the Tuba Drain. It will be important to ensure that the solder joint is a neat, accurate one, that doesn’t create a lump in the lumen, or a dip due to an unfilled gap between the pipes. We are currently working on producing the bent Tuba Drain. The approach should be working in the next two months, so we should be able to mass produce them by this September.
The Tuba Drain is a simple, cost-effective, low-maintenance approach for preventing the ascent of bacteria from traps to sinks. It should be incorporated in new hospitals, and — where possible — added to existing sink drains in old hospitals. Not all resistance is transferred in hospitals, and it will also have a role in care homes, airports, railway stations, and hotels. Ultimately it may be used as standard drainage of every sink. Great Ormond Street Hospital has applied for a UK patent, and may extend that globally. If Tuba Drains are introduced globally, along with other measures to limit environmental spread, and further efforts are made to decolonise the guts of people who are carriers of resistant bacteria (already demonstrated to be effective against Vancomycin-resistant Enterococcus), I can see no reason why we should not reverse the rise of antibiotic resistance, but it will require the will, effort, and investment, of those controlling health services. The WHO estimated that bacterial AMR was directly responsible for 1.27 million global deaths in 2019, and contributed to 4.95 million deaths.5 The World Bank estimates that AMR could result in US$ 1 tn in additional healthcare costs by 2050, and US$ 1 tn to US$ 3.4 tn gross domestic product (GDP) losses per year by 2030.6 A bit of investment and effort is likely to be worthwhile.
James Soothill
Dr James Soothill MBBS, MD, FRCPath, has worked as a Consultant Microbiologist at Great Ormond Street Hospital for Children in London for the past 25 years. His work includes advising on the prevention, diagnosis, and management, of hospital infection, and his interests include measures to control the transmission of antibiotic-resistant bacteria, including the use of probiotics and bacteriophages to control gut carriage. He initiated a pioneering treatment at Great Ormond Street Hospital using Genetically modified bacteriophage that received widespread media coverage. He reports that his work to prevent central venous catheter-associated infections via the use of chlorhexidine wipes on line ports reduced the number of infections to one-third of what it had been, ‘with a huge financial saving’.
References
1 The Silent Pandemic: Antimicrobial Resistance and the Need for Better Hospital Design. Healthcare Infection Society, 18 June 2025. https://tinyurl.com/4znf5yvn
2 Kizny Gordon A, Mathers A, Cheong E, Gottlieb T, Kotay S, Walker A et al. The Hospital Water Environment as a Reservoir for Carbapenem-Resistant Organisms Causing Hospital-Acquired Infections-A Systematic Review of the Literature. Clin Infect Dis 2017; 64(10):1435-1444.
3 Kotay SM, Donlan RM, Ganim C, Barry K, Christensen BE, Mathers AJ. Droplet- Rather than Aerosol-Mediated Dispersion Is the Primary Mechanism of Bacterial Transmission from Contaminated Hand-Washing Sink Traps. Appl Environ Microbiol 2019; 85(2): 1997-18.
4 Harris S, Njogu G, Galbraith R, Galbraith J, Hastick S, Storey N et al. A ‘Tuba Drain’ incorporated in sink drains reduces counts of antibiotic-resistant bacterial species at the plughole: a blinded, randomized trial in 36 sinks in a hospital outpatient department with a low prevalence of sink colonization by antibiotic-resistant species. J Hosp Infect 2025; Jan: 155:123-129. Epub 2024 Nov 6. PMID: 39515476.
5 Antimicrobial Resistance Collaborators. Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis. The Lancet 2022; 399: 629-655.
6 Drug-Resistant Infections: A Threat to Our Economic Future. World Bank Group, March 2017. https://tinyurl.com/4f9ujh5k