The following video presentation deals with Pseudomonas aeruginosa water testing and sampling methods in hospitals, health and social care environments, with particular emphasis on augmented care units. It includes commentary from two leading experts in this area, Peter Hoffman – Consultant Clinical Scientist – Public Health England and Jimmy Walker – Water System Microbiology Expert – Public Health England.
Pseudomonas aeruginosa is something that most people come across many times each day and it does them no harm. However, some people in hospitals have very reduced immune systems either because of their disease or therapeutic process.
Prioritising Augmented Care
It’s very important that samplers understand that they do not have to take samples right across their hospital. And where they need to concentrate on is the adult paediatric and neo-natal intensive care units which are very good examples of augmented care units where the sampling has to be prioritised and focused because it is most important for patient care.
It [Pseudomonas aeruginosa] is very metabolically adept, it can live almost anywhere it is wet, it can survive on a whole range of carbon compounds so it can survive on very little and thrive.
Sampling Water Systems, Shower Heads & Taps
Pseudomonas aeruginosa, because it is an environmental organism thrives in water systems particularly where there is an oxygenated area at the end of a tap or a shower head, and in these particular environments what it does is that it will attach to the surface of any of the components of the taps or shower heads and grow what is called a biofilm where the organisms grow and produce an exopolysaccharide which acts like a glue and adheres them all together on that surface.
In sampling the water what you will find is the free swimming forms that are given off by a biofilm. These free swimming forms will build-up over a biofilm with time. So if you sample a tap which hasn’t been used for several hours then these free swimming forms will have built up and you will find them in the water you sample.
Understanding the Differences between Sampling for Pseudomonas aeruginosa & Legionella
It’s vitally important that people understand the difference between sampling for this [Pseudomonas aeruginosa] and Legionella. With Pseudomonas what you do, is you do not disinfect the outside of the tap, you take the first part of the water sample in to a container, a sterile container and you take a couple of hundred mils in to that container and send it off to the laboratory.
Testing for Pseudomonas aeruginosa with shower heads is slightly different, what you have to be able to do is contain the water coming from the shower, because what you don’t want it to do is dispersing over the environment. What you do is tie a sterile bag round the head of the shower and you then cut the corner off, hold the bottle underneath and flow the water through the bag in to a sterile container, and you take a couple of hundred mils in to that container and send it off to the laboratory.
Filter Testing for Pseudomonas aeruginosa
The water then goes off to the laboratory who will put a measured volume of that water through a filter that will allow the water through but retain bacteria. That filter is then put on a solid growth medium which will supress non- Pseudomonas aeruginosa but allows Pseudomonas aeruginosa to grow and then you can count the numbers of Pseudomonas aeruginosa that there were in a particular volume of water.
Pseudomonas Positive Tests
If you do find Pseudomonas aeruginosa positives in the samples, what you do is you go back and take another two samples. Basically you want to take what we call the first sample which is pre flush, so it’s immediately and without disinfectant outlet at the tap, and then you flow the water through the tap for two minutes and then you take another sample which is called a post flush. And what you are doing there is trying to find out where in the water system the Pseudomonas aeruginosa is actually present.
Identifying the Source of Pseudomonas Contamination
If there were lots of Pseudomonas aeruginosa in the first sample and also in the second sample then you have contamination throughout the system. If there are a lot of Pseudomonas Aeruginosa in the first sample but very few in the second sample then you are looking for a source at or very close to the point of water discharge.
The results of water filtration sampling can take several days to arrive. If the hospital is in urgent need of rapid results it can swab tap outlets. This won’t detect Pseudomonas aeruginosa colonisation if it’s further back in the system but it will let you know if there is colonisation at the water outlet itself.
Pseudomonas Aeruginosa: Method for obtaining water samples – Public Health England
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