Biofilm formation in dental unit waterlines and the resulting microbial contamination of the water in the system has become a significant problem. Contaminated water in the dental units is a major concern in dental clinics due to potential risk of causing infections particularly in elderly and immunocompromised patients. The aim of this study was at first to determine microbial contamination of the dental unit waterlines and then to study the efficacy of a comprehensive disinfection protocol on decreasing the microbial load. Water samples were collected before and after disinfection procedure from handpieces and water storage bottles from the dental units, a small 1-cm tubing was cut from each unit and subjected to microbiological culture on different growth media. Identification of the predominant species was achieved by 16S rRNA gene sequencing. Microbial growth was observed in samples collected from all dental units. Upon disinfection procedure, microbial contamination in the water samples and in the tubing surfaces was significantly reduced (P > 0.05). 16S rRNA gene sequencing revealed the presence of several species belonging to the genera Staphylococcus, Corynebacterium and Roseomonas, some of which are implicated in human infections. Aggravation of the biofilm growth on the tubing surfaces and the microbial contamination in the water can be effectively controlled by implementing appropriate and routine disinfection protocols. This may help protect the dental unit staff and the patients being exposed to the risk of infections.

UNASSIGNED: Many studies consider the contamination of dental unit waterlines (DUWLs), but few of them have studied the possible presence of antibiotic resistant Pseudomonas aeruginosa in the DUWLs.
UNASSIGNED: Investigation of the presence of P. aeruginosa and Pseudomonas spp. strains in DUWLs and evaluation of their resistance to six antibiotics (ceftazidime, netilmicin, piperacillin/tazobactam, meropenem, levofloxacin, colistin sulfate) at a public dental clinic in Milan, Italy.
UNASSIGNED: Dental units were contaminated by P. aeruginosa with loads of 2-1,000 CFU/L and were mainly located on the mezzanine floor, with a range of 46-54%, while Pseudomonas spp. were primarily found on the first and second floors, ranging from 50 to 91%. P. aeruginosa was antibiotic resistant in 30% of the strains tested, andPseudomonas spp. in 31.8% . Cold water from controls was also contaminated by these microorganisms.
UNASSIGNED: Monitoring antibiotic resistance in the water and adopting disinfection procedures on DUs are suggested within the Water Safety Plan.

Bacterial contamination of dental unit waterlines (DUWLs) was evaluated using ATP bioluminescence analysis and a conventional culture method. Water samples (N=44) from DUWLs were investigated for heterotrophic bacteria by culture on R2A agar, which gave counts ranging from 1.4×103 to 2.7×105 cfu/mL. The ATP bioluminescence results for DUWL samples ranged from 6 to 1189 relative light units and could be obtained within 1min; these correlated well with the culture results (r=0.727-0.855). We conclude that the results of the ATP bioluminescence assay accurately reflect the results of conventional culture-based testing. This method is potentially useful for rapid and simple monitoring of DUWL bacterial contamination.

Bacterial contamination in dental unit waterlines (DUWLs) was evaluated by molecular techniques in addition to the conventional culture method. Water samples (n=8) from DUWLs were investigated for heterotrophic bacteria by culture method using R2A agar. The selected bacterial antibiotic-resistance genes and Legionella species-specific 16SrDNA were identified by PCR. The profiles of bacterial contamination in DUWLs were further identified by PCR-DGGE. In this study, no antibiotic-resistant or Legionella genes were detected. Polycyclic aromatic hydrocarbon-degrading bacterium, Novosphingobium sp. was the most prevalent in DUWLs. Conventional PCR and PCR-DGGE were shown to be potentially useful for monitoring of bacterial contamination in DUWLs.