What is Biofilm?
When people think of bacteria in water systems, an image of a single floating microorganism floating in water often springs to mind. However, most bacteria do not drift in isolation in this way. Around 90% of Legionella bacteria can be found within sessile communities on the inner surfaces of pipework and other wet surfaces.
These sludgy surface layers, which are created as bacteria attach to surfaces and create a polysaccharide matrix, are called biofilms. Biofilm is a layer of organisms, usually made up of bacteria, protozoa and algae which groups microorganisms together on wet surfaces.
As a result, biofilm is ubiquitous. It is present in practically every managed water system, lining the interior of taps, showerheads, pipes and tanks. In your home, place of work and every building you visit.
Why is Biofilm bad for your system?
Within biofilm, bacteria such as Legionella need less oxygen and fewer nutrients to replicate. This slime-like layer can also protect micro-organisms from disinfection and biocides by providing a physical barrier from treatments, allowing pathogens like Legionella to proliferate.
Within water systems, dense biofilm formations can break apart and pieces can be carried off to other areas of the system, getting clogged in dead legs and filters and compromising further sections of the system. A build-up of biofilm can also have an adverse effect on heat transfer efficiency and can act as a catalyst for corrosion.
Recent research suggests that biofilm can affect Legionella’s virulence (its ability to infect amoeba) which are invaded by Legionella in much the same way as human lung cells. Data indicates that Legionella which originate from biofilm can avoid innate immune responses in macrophages thus allowing for more successful infectivity.
The above factors can significantly increase the risk of Legionnaires’ disease outbreaks and the implications for business and public health are severe. Around 1 in 10 people who are infected with Legionnaires’ disease will die. This fatality rate can be as high as 1 in 4 in hospitals and other facilities where many immunosuppressed persons are present.
Outbreaks can have financial and reputational consequences for businesses, often resulting in fines, litigation, bad press, loss of profit and in some cases even incarceration.
How does Biofilm effect Legionella testing?
Research suggests that due to the agreeable conditions provided by amoeba about 90% of Legionella live in biofilm formations and only can be found 10% suspended in the water running through the system.
Legionella pneumophila has two distinct phases to its life cycle: the replicative phase where it multiplies and the motile, dispersal phase, where it is looking for a new host and moving freely in the water system.
Unless biodispersant has been added to the system by a water management professional to loosen biofilm, biofilm residing Legionella will remain within the amoebic host environment until it has exhausted the resources of its host. Once this has happened it will revert to the motile dispersal phase and break through the amoeba cell wall to seek a new host.
This has serious implications for Legionella testing. Firstly, because the amount of Legionella captured from free-flowing water during sample collection may drastically underestimate the total Legionella count in the system as a whole, because only a small fraction of the bacteria is available from free-flowing water.
Secondly, only certain phases of the Legionella lifecycle are easily replicable via the most commonly used Legionella testing method, laboratory culture. Therefore, the success of the lab culture test is at least partially dependent on the lifecycle phase of the bacteria present in the sample, at the time of testing.
The most hazardous phase (referred to above as the motile phase), is the phase in which Legionella can infect human lungs. Ironically, this phase cannot be easily replicated via the culture method because the bacteria is not in a naturally replicative state. For this reason, the laboratory culture method can be a very poor tool for detecting positive results.
How to Mediate Biofilm Growth?
Biofilms are optimized for bacteria growth and survival and are therefore difficult to eradicate. However, there are some measures you can take to reduce biofilm build up and protect your facility from Legionnaires’ disease risk.
Firstly, low flow encourages the growth of biofilm and Legionella colonisations and has been linked to Legionnaires’ disease cases in hospitals. Removing dead legs, flushing systems which are not in regular use and implementing constant system flow can all contribute to the reduction of biofilm formations.
Consider the materials used within your system wisely as some are more prone than others to biofilm formation (and may even be a more influential factor for biofilm growth than the presence of organic matter). For example, research shows that bacterial counts on iron pipes are usually higher than on PVC pipes.
Water systems can be treated with a range of biocides, copper and silver ionisation, UV and Ultrasound technology. Treating and disinfecting your water system will kill and inactivate Legionella and other bacteria in your system and will help to minimize growth of biofilm which supplies Legionella with protection and nutrients. To release biofilm from the inner surface of your pipes, a biodispersant can be used alongside your chosen treatment.
Filtration may also be useful in systems where water is recirculated, where system efficiency is critical or where water source quality is poor. Filtration of water entering a system can remove particulates and organic matter, reducing the rates of biofilm formation and Legionella growth.
Test Your Biofilm with a Swab Test Kit
If your system has a Legionella population it will be found in the system’s biofilm. Get a more complete view of what is going on in your system with the Hydrosense Legionella Swab Test. With this kit, anyone can test biofilm deposits for Legionella on-site and in receive results in 25 minutes rather than 7-14 days.
The risk of acquiring Legionnaires’ disease can increase by 64% for every hour spent near the source of an outbreak and testing is the only way to ensure systems are kept safe, so a fast test like Hydrosense is a critical part of your Legionella risk management toolkit.
Watch our Technical Director, Richard Campbell, demonstrate just how easy the test is!
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