Curing pathogens in the pipes
The typical hospital houses large numbers of people in close confines, many with compromised immune systems and all reliant on the same water supply infrastructure.
Over time, microbes build up in the plumbing system of such an environment, and vulnerable patients are exposed to bacteria strains that would not harm a healthy person but can prove deadly to those with weakened immunity.
Between 2004 and 2005, six premature infants died in a neo-natal ward at Centre Hospitalier Universitaire (CHU) Sainte Justine in Montreal, Canada.
Following the first death, the hospital conducted an investigation and was unable to find the infection source. The ward, which had been overcrowded, was disinfected and remained open. Additional deaths over an 18-month period triggered the closure of the ward, and a subsequent investigation identified festering, blocked sinks and a corroded plumbing system as the source of a bacterial colony of pseudomonas aeruginosa.
It was reported by Radio Canada that 50 patients had been exposed to infection, including the six infants, and that they had contracted it from water carrying the bacterium.
Pseudomonas aeruginosa, a waterborne pathogen, thrives in harsh conditions and attacks the respiratory system, causing pneumonia and septicaemia in immuno-compromised patients. The bacterium commonly exists in the environment and does not pose a risk to healthy people. However, there is a mortality rate of up to 40% when it is transferred to newborns, the elderly and patients with immune systems weakened by illness or operation – and an incalculable cost to a hospital’s reputation.
University of Pittsburgh special pathogens laboratory director Dr Janet E. Stout says patients in transplant units, haematology, oncology, burns, neo-natal intensive care and other intensive care units are at greatest risk of waterborne infections and need very high quality water.
The US-based Committee to Reduce Infection Deaths (RID) estimates that 100,000 people will die this year from infections acquired in hospital. Patients come into contact with waterborne bacteria, or pathogens, not only through ingestion, but also bathing, ice cubes for mouth sores, inhalation of shower mist or being treated with instruments washed in hospital water.
Dr Stout, an international expert on waterborne pathogens, notes that no single systemic disinfection technology can completely eliminate these micro-organisms from hospital plumbing systems. Many of the microbes live in biofilms – communities of micro-organisms that adhere to the pipes and are resistant to systemic disinfection treatments.
“We are interested in waterborne pathogens for two reasons – because they can cause infections, particularly in immuno-compromised patients, and because they are increasingly becoming resistant to antibiotics,” she says.
“About 50% of the plumbing systems of large buildings – hospitals, hotels, offices – are colonized with bacteria such as legionella and pseudomonas aeruginosa. We need to reduce point-of-source exposure to prevent these bacteria colonizing people, in order to reduce the risk of creating drug-resistant bacteria through the over-use of antibiotic treatment.”
In other words, prevention is the key.
Dr Stout believes the most effective way of protecting hospital patients is point-of-use filtration.
“The efficacy of point-of-use filtration in preventing against micro-organisms was demonstrated in a 2005 study.
Mycobacteria, total heterotrophic plate count (HPC) bacteria and legionella were completely eliminated by the filter at the point of use for up to 14 days.
“Another interesting lesson from studies conducted in the last few years is that sensor-operated faucets with a hot and cold water mixing valve – which are traditionally viewed as more hygienic because there is no contact made with the faucet – can actually be a more viable breeding area for certain types of bacteria than conventional faucets.
“The reason for the problem with non-touch electronic or sensor faucets is the stagnation of water at the faucet’s electronic shut-off valves, and the heating and subsequent incubation of pathogens in those valves. The warm temperature in the mixing chamber of the faucet is conducive to the growth of bacteria. Of 38 non-touch taps tested, 74% were contaminated with pseudomonas aeruginosa and 100% with legionella.”
But this does not mean that sensor faucets and mixing valves don’t have a place in hospitals. Good initial design is important – engineers and designers need to know the function of each ward and where various devices are used, and to factor these end-uses into their plans.
“Sensor faucets have a range of important applications in a hospital, but on wards with immuno-compromised patients it is important to minimize the likelihood of waterborne pathogens coming into contact with patients, as there are serious risks associated with these devices,” Dr Stout says.
Plumbing engineers should be aware of the sorts of modifications that need to be made to older pipework to ensure a sanitary system and good drainage. Redundant pipework and cisterns should be removed, as bacteria breed in such places.
“Waterborne microbes may be harbored by amoebae that shelter them and safely transport them to hard-to-reach areas of the hospital’s plumbing system,” Dr Stout says.
“On high-risk wards, water needs to be delivered hot, and pipe runs must be kept as short as possible to avoid the risk of water stagnating in pipes. A combination of techniques is required, and this means good plumbing design and use of materials, and regular disinfection.
“Pathogens can attach and colonize the surfaces of many materials used in water systems, including rubber, PVC and wood surfaces in high concentrations. The removal of such materials has been suggested as a means of reducing bacteria in a plumbing system, but this approach has not been scientifically validated.”
Dr Stout’s team is investigating the bacteria-inhibiting effects of copper-silver ionization systems and chlorine dioxide. Copper-silver ionization involves releasing copper and silver ions, usually into a recirculating hot water system.
“Studies have shown this method to be very effective. Chlorine dioxide is a relatively new technology whereby sodium chlorite is converted into chlorine dioxide electrolytically, producing a small volume at a relatively low concentration. It is injected directly into the hot and cold water to control waterborne pathogens. “
American Society of Sanitary Engineering (ASSE) international past president and Cleveland Clinic facilities engineer Edward Lyczko believes that regular plumbing and general maintenance is vital in the fight against infectious disease.
“In older hospitals, the drain lines must be inspected for leakage. The bacteria that infected the infants at Sainte Justine apparently came directly from the drains. Leaking drains, especially from inside walls, can also result in mould.
“Hospitals need to conduct a regular drain maintenance program to make sure there is a free flow through them. This should involve periodic dumping of an approved, non-toxic liquid drain maintainer, or periodic ‘mechanical’ maintenance such as plunging or snaking.
“When any of these methods are used, they must be performed inside a completely surrounding temporary approved barrier from floor to ceiling. An approved high-efficiency particulate air (HEPA) filter unit should be fitted inside the barrier. This will create negative air pressure, preventing any air contamination inside the barrier from escaping into the room. This barrier must also be used any time ceiling tiles are removed or walls penetrated.”
Routine checks should be carried out on all existing plumbing.
“All drains should be periodically swabbed and tested for bacteria,” Lyczko says.
“If there are bacteria present, an appropriate and approved germicide must be used. To protect the potability of water, the entire hospital must have an approved backflow prevention program. To prevent bacteria growth in faucets, all spout-end aerators must be removed. The entire spout should be replaced with an approved integral flow control device that will limit flow to prevent splashing without harboring bacteria.”
Lyczko recommends a holistic approach to facilities engineering to contain the spread of bacteria in hospitals, and this extends beyond plumbing.
“In newer buildings, correctly installed fire-stopping techniques will indirectly prevent the spread of bacteria because all walls are extended up past the ceiling to the bottom of the next floor or the roof. Pipe chases are sealed at each floor and all penetrations are sealed with fire stopping caulk. This prevents any air circulation across ceilings to other rooms or up pipe chases to different floors, and it will stop the spread of disease throughout the building.
“In older buildings the necessary funds must be allocated to bring fire stopping up to modern codes and to update plumbing systems.”
Beyond regular maintenance and general hygiene, solutions should be tailored to the needs of each ward.
“System-wide disinfection may not always be the best answer,” Dr Stout says.
“A targeted approach – short-term and long-term – may meet a hospital’s needs more effectively. Filtration can be quickly implemented in an outbreak situation and can also be used long term in high-risk areas for maximum protection.”
For CHU Sainte Justine, the problem has been hard to resolve. It is not easy to overhaul a busy 50-year-old hospital without interruptions to its vital services, and the transformation may take some time.
The Canadian Public Health Department says current immuno-compromised patients have no contact with the mains water system at the hospital at all, whether for washing or drinking. Meanwhile, the hospital is renovating the neo-natal ward, which will open next year.