Research abstract
British Dental Journal 196, 157 - 159 (2004)
Published online: 14 February 2004 | doi:10.1038/sj.bdj.4810943
Verifiable CPD Paper:
Total viable counts, ATP, and endotoxin levels as potential markers of microbial contamination of dental unit water systems
M R Fulford1, J T Walker2, M V Martin3 & P D Marsh4
- Almost half of dental unit water systems (DUWS) sampled harboured viable microorganisms at levels greater than current guidelines.
- Total viable counts are still the most reliable marker of contamination, even though they underestimated the total microbial load.
- Endotoxin levels in water were low.
- ATP is a very rapid method of indirectly detecting the microbial load, but the method is currently not sufficiently sensitive to reliably detect the normal levels of microbes in DUWS.
Abstract
Objectives To determine if either ATP or endotoxin concentrations in water supplied by dental unit water systems (DUWS) correlated with total viable counts (TVC), and therefore could be used as a rapid, chairside measure of levels of microbial contamination.
Design A prospective trial.
Method Fifty-seven water samples were taken from the 'triple spray', air rotor and source water supplies from 25 dental units in eight practices. The samples were assayed for endotoxin concentration, total ATP and TVC. A pilot study was performed to assess the relationship between TVC and total cell counts, as determined by flow cytometry.
Results ATP concentrations ranged from 22 to 958 relative light units (RLU) and free endotoxin ranged from 25 to 600 EU ml-1. TVC varied from not detected to 2.16 
104 CFU ml-1. The ATP method proved to be a simple and rapid method that could be used at the chairside. However, there was no correlation between ATP or endotoxin concentrations and TVC in DUWS. TVC generally underestimated the total cell count by 50 to 500 fold.
Conclusion Half of the water samples from DUWS exceeded recommended levels of TVC. However, ATP and endotoxin concentrations in DUWS water samples did not correlate with these TVC data and therefore could not be recommended as an alternative assay to TVC for measuring bacterial contamination or for monitoring water treatment efficacy.
- GDP, 10 B Lower Downside, Shepton Mallet, Somerset, BA4 4JX
- Project Team Leader, Health Protection Agency, Porton Down, Salisbury SP4 4JG
- Senior Lecturer and Honorary Consultant Microbiologist, Department of Clinical Dental Sciences, University of Liverpool, Liverpool L69 BX
- Professor and Scientific Leader, Health Protection Agency, Porton Down, Salisbury SP4 0JG and Professor of Oral Microbiology, Leeds Dental Institute, Leeds LS2 9LU
Correspondence to: J T Walker2
Health Protection Agency, Porton Down Salisbury; SP4 0JG;
e-mail: jimmy.walker@hpa.org.uk