The enemy within

The importance of tackling dangerous bacteria in hospital water systems

Hospital water systems can be a breeding ground for dangerous bacteria. Richard Sinden, life sciences product innovation and regulation director at SUEZ, explains the importance of tackling this bacteria and the challenge of keeping systems safe

Failures in the design, operation, maintenance, or monitoring of manmade water systems can allow bacteria to thrive. In the healthcare environment, where patients may have suppressed immune systems, or where their bodies’ natural barriers may be breached by wounds or surgery, the risk this presents is particularly acute.

Legionella bacteria, for example, can cause Legionnaires’ disease, a difficult-to-treat form of pneumonia, if inhaled in water droplets. Pseudomonas aeruginosa , another category of pathogen, can infect almost any part of the body, from the skin to the central nervous system.

The law requires the dutyholder in any healthcare establishment to assess the health risks posed to its water supply

The threat from these organisms is very real. Between 3,700-4,000 P.aeruginosa infections are reported to the Health Protection Agency every year, and the fatality rate for hospital-acquired Legionnaires’ disease is close to 50%.

The UK has strong regulatory frameworks governing the design and operation of water supply systems. The HSE document Legionnaires’ disease: The control of legionella in water systems is the approved code of practice in the UK. The document has legal status under the Health and Safety at Work Act and the Control of Substances Hazardous to Health Regulations. Health Technical Memorandum HTM-04-01, from the Department of Health, outlines the principles involved in the design, installation and testing of hot and cold water supply, storage, and distribution systems in healthcare premises. The HTM-04-01 Addendum provides best-practice advice for tackling the risks from P.aeruginosa in augmented care units.

The basis of good practice in water supply system design is to remove the conditions that promote bacterial growth. This involves controlling water temperatures so all parts of the system are below 20°C in the case of cold water supply or above 55°C for hot water, ensuring sufficient throughput to prevent stagnation, and minimising the occurrence of contaminants, such as rust or debris. Strategies to achieve these objectives include minimising the overall length of pipe work, removing dead-legs or rarely-used fixtures, and installing trace heating on hot water return legs where lower temperatures may occur.

While Legionella bacteria enter the water system of a building from the external supply, P.aeruginosa is far more opportunistic. It can survive away from a water source for several hours and can enter water systems via outlets within the building, such as taps and shower heads, and colonise the pipework close to these fittings.

Relying on temperature alone to kill P.aeruginosa is difficult. As the water temperatures necessary to prevent bacterial growth in hot water distribution systems can present a risk of scalding to vulnerable users, it is recommended practice to install thermostatic mixing valves to control the final temperature of water at the outlet. The design and location of these devices can, however, increase the risk of colonisation by P.aeruginosa, potentially calling for more monitoring and routine maintenance.

The law requires the dutyholder in any healthcare establishment to assess the health risks posed to its water supply. They must appoint competent persons to conduct this assessment to take responsibility for an appropriate risk control scheme and to keep detailed records. The risk assessment should include a clear allocation of management responsibilities, evidence of the competence and training of key personnel, a description of the water system (including a schematic diagram) and procedures for the operation, monitoring, inspection and maintenance of the system. The assessment must be updated regularly, especially if the design or use of the system changes.

Ongoing risk management should include regular sampling of water at all outlets within a facility. Where P.aeruginosa contamination is detected, remediation actions include the removal of items like flow straighteners, or flexible connectors that can provide a habitat for bacterial growth, together with measures to reduce the splashing that can lead to contamination of outlets in use. In some circumstances it may be necessary to carry out a disinfection of the water supply system. Modern high-performance biocides have been shown to give very effective results against both Legionella and Pseudomonas aeruginosa, combined with a low-hazard classification and good environmental profile.

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