Bacterial Diversity Found in Dental Unit Waterlines Using Pyrosequencing

Objectives: Water from the waterlines of dental units is often contaminated with bacteria but there have been few studies accurately assessing the diversity of these bacterial populations. The aim of our study was to assess the bacterial diversity present in water collected from dental unit waterlines using pyrosequencing.
Methods: Water was collected from two separate dental units located in a dental hospital and two units found in two separate private clinics in Gangneung-si, Korea. Samples were filtered through a 0.2 µm pore-size filter to isolate bacteria. Genomic DNA was then extracted using a Genomic DNA Extraction Kit. Pyrosequencing was carried out using an Illumina MiSeq Sequencing system. A taxonomic classification for each read was then assigned from the EzTaxon-e database (www.ezbiocloud.net).
Results: From the four water samples that were analyzed, a total of 233 bacterial genera were identified. The most abundant genera were Sphingomonas (25%), Halomonas (20%), Reyranella (8%), and Novosphingobium (6%). Halomonas was more prevalent in the two dental units located at the dental hospital, while Reyranella and Sphingomonas were more commonly found in the private dental clinics. Only 19 of the 233 identified genera were common between water samples from all dental units. Opportunistic pathogens were shown to account for 7.7% of the total bacterial genera identified.
Conclusions: Our results have demonstrated that there is a wide assortment of bacterial genera present in dental unit waterlines and that these populations can differ depending on the supply tank for the dental unit.