It’s February. It’s cold and dark, the Christmas bills have dropped through the letterbox and summer seems a very long way away. It’s the time when enthusiasm for New Year’s resolutions can easily wane, the gyms that were packed during the first weeks of January will have returned to normal levels, as the majority of new members retreat back to the comfort of their sofa.
The problem is that good intentions are not on their own enough to be successful - no one achieves physical fitness by visiting the gym once or twice, the intention needs to be supported by processes that mean that good habits become part of one’s normal routine. This analogy can also apply to the processes that take place in a dental practice and are particularly applicable in terms of infection control procedures, which should be routinely carried out on a regular basis to ensure compliance with regulations. The control of biofilm, that can rapidly build in dental unit waterlines (DUWLs) is an ideal example of a procedure, that if undertaken regularly, will show positive results in a relatively short period of time. The control and eradication of biofilm is essential if practices are to comply with infection control guidelines and should be seen not only as a means of disturbing the growth of pathogenic bacteria, but also as a means of protecting patients and staff from potential infection due to either direct contact or inhalation of aerosolised mist expelled from handpieces.
Biofilm forms when microorganisms attach themselves to surfaces in aqueous environments, secreting a slimy substance that anchors to metal and plastic, especially within the piping and tubing in water delivery systems. Because the tubing is small in diameter it means that the surface area is large relative to the volume of water that passes through it and this allows a much faster build-up rate of microbes. If left untreated the biofilm will flake off the inside of the tube and release potentially high doses of microbes into the water supply, causing water quality levels to fall below those required by HTM 01-05 guidelines.
So, just as an occasional visit to the gym will not make you into a top athlete, thinking that an occasional treatment of DUWLs will solve the problem of biofilm is misguided. Just like making a New Year resolution to do regular exercise, the regular cleaning and maintenance of
DUWLs needs to form part of routine infection control processes in order to be successful.
There is a combination of reasons why DUWLs provide an ideal environment for the growth of biofilms, starting with the fact that the materials used in the tubing are specifically non-toxic, meaning if they are not toxic to humans, the bacteria are unaffected as well. The small bore tubes have a low water flow rate (typically 30ml/min) and this is ideal for bacterial adhesion and because the water flows only when instruments are in use, there is little to disturb the growing biofilm. In addition the presence of biofilm can in itself lead to a reduction in water flow within the system and increases the potential for eventual tube blockage resulting in unit downtime and repair costs.
When fresh liquid is added into the unit, for instance when instruments are used or the system is flushed, fresh nutrients are introduced to the system and join the growing biofilm.
As this is washed down towards the distal end of the system it carries bacteria released by the maturing film along with excreted matter. At the same time the surgery environment itself, normally maintained at room temperature for the comfort of patients and staff, provides an ideal climate for the film-forming bacteria to thrive.
HTM 01-05 guidelines recommend various measures to help reduce the presence of biofilm, including the emptying and storage of water bottles at the end of each working day and the flushing of water lines for two minutes at the beginning and end of the working day and after breaks. They also recommend the lines should be flushed for 20-30 seconds between patients, but despite this the guidelines also acknowledge that flushing has little effect on biofilm build-up.
In order to effectively control and prevent biofilm a practice must instigate rigorous treatment and monitoring procedures, thereby ensuring full compliance with the relevant local guidelines and providing peace-of-mind for those with infection control responsibilities. Regular monitoring of input and output water is a simple process to undertake using dip slides and gives a reasonably accurate indication of whether further treatment is required. For those preferring an immediate reading of contamination levels, an ATP system provides a digital reading, which can be converted to cfu/ml and recorded as appropriate. There are also now third party laboratory services that will measure samples of input and output water and return results to the practice normally within seven days, where they can again be recorded as required.
Whichever technique is chosen to assess water quality, it is the regularity with which the process is carried out that is the key variable. So even if your personal New Year resolutions are not going quite as well as planned, you can make a resolution to minimise biofilm contamination in DUWLs in your practice simply by making the control and monitoring a priority and a regular part of your routine infection control procedures.