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Tips On How To Avoid Contacting Legionnaires' Disease
Legionella Risk Assessment
Date: 3/27/2019 5:07:27 PM ( 5 y ) ... viewed 419 times The presence of bacterial biofilms in dental water lines is well documented and the origin of supply is considered to be the planktonic organisms present in the supply water. The dental unit with its long, narrow bore appears to be a good environment for the formation of a biofilm. The bacteria in any biofilm show greater levels of physiological activity and enhanced resistance to biocides Legionella Risk Assessment. Biofilm formation results in a tenacious layer that is strongly adherent to the side walls of the tubing and frequently contains many different types of pathogenic bacteria.
In fact several pathogens such as Pseudomonas, Mycobacterium and Legionella have been isolated from dental unit water lines (DUWL). Some of these bacteria can be responsible for severe diseases, and immuno-suppressed clients in particular are at high risk. There is also a direct link between contaminated dental water lines and occupational asthma in dentist's.
In general it is not hard to find practices with dental water line contamination, even with the presence of an on-going cleaning and disinfection regime.
Recent research has shown that these disinfection and cleaning regimes are often ineffective due to the inability of many biocides to remove this biofilm. This may be due to microbiological resistance to many of the organic biocides and in fact the most effective biocide tested in the research was 5% sodium hypochlorite. Sodium hypochlorite is an extremely potent biocide and due to the oxidising action of the biocide it is not possible for bacteria to gain resistance. The oxidising nature of the biocide will also react with and breakdown the polysaccharide, lipid and protein components of the biofilm, thus removing it.
It has been suggested that biocide resistance may be due to plasmid transfer, i.e the transfer of resistance from one bacteria to another through the transfer of small portions of DNA. Plasmid transfer combined with a high rate of natural mutation under adverse conditions means that dental water lines will always be liable to biofilm formation.
In order to ensure that biofilm formation is minimised there are a number of practices that need to be implemented. Firstly, if currently using only a single biocide, a multiple biocide therapy should be used in order to prohibit the build-up of resistance and it has been clearly shown that twin biocide therapy can lower biofilm presence by 98% compared to a single biocide reduction of between 16% and 92%, dependent on biocide used.
Secondly, routine sampling of dental water lines for total bacterial numbers should occur to determine if contamination is present. Simple TVC testing at 22 C and 37 C will provide accurate numbers of micro-organisms and will provide details on the amount, if any, of contamination. TVC testing is reasonably cheap and is available from many labs around the country; expect to pay between 10-25 pounds per sample but ensure any lab used is accredited under the UKAS scheme.
Whilst dipslide sampling has been suggested by some it has neither the accuracy or low end resolution capability, thus providing little value in terms of on-going management of contamination.
By implementing these practices dental water lines can be maintained biofilm free, resulting in the improved health of all those in contact with them.
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