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Appl. Environ. Microbiol., 11 1996, 3954-3959, Vol 62, No. 11
J Barbeau, R Tanguay, E Faucher, C Avezard, L Trudel, L Cote and AP Prevost
Microbial contamination of dental unit waterlines is thought to be the
result of biofilm formation within the small-bore tubing used for these
conduits. Systematic sampling of 121 dental units located at the dental
school of Universite de Montreal showed that none of the waterlines was
spared from bacterial contamination. Multilevel statistical analyses showed
significant differences between samples taken at the beginning of the day
and samples taken after a 2-min purge. Differences were also found between
water from the turbine and the air/water syringe. Random variation occurred
mainly between measurements (80%) and to a lesser extent between dental
units (20%). In other analyses, it was observed to take less than 5 days
before initial bacterial counts reached a plateau of 2 x 10(5) CFU/ml in
newly installed waterlines. Sphyngomonas paucimobilis, Acinetobacter
calcoaceticus, Methylobacterium mesophilicum, and Pseudomonas aeruginosa
were the predominant isolates. P. aeruginosa showed a nonrandom
distribution in dental unit waterlines, since 89.5% of the all the isolates
were located in only three of the nine clinics tested. Dental units
contaminated by P. aeruginosa showed significantly higher total bacterial
counts than the others. By comparison, P. aeruginosa was never isolated in
tap water remote from or near the contaminated dental unit waterlines. In
conclusion, dental unit waterlines should be considered an aquatic
ecosystem in which opportunistic pathogens successfully colonize synthetic
surfaces, increasing the concentration of the pathogens in water to
potentially dangerous levels. The clinical significance of these findings
in relation to routine dental procedures is discussed.
Copyright © 1996, American Society for Microbiology
Multiparametric analysis of waterline contamination in dental units
Departement de stomatologie, Faculte de medecine dentaire, Universite de Montreal, Quebec, Canada. barbeauj@medent.umontreal.ca
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