M.J. O’Donnell et al. A centralised, automated dental hospital water quality and biofilm management system using neutral EcasolTM maintains dental unit waterline output at better than potable quality: A 2-year longitudinal study. JOURNAL O F DENTISTRY 37 ( 2009 ) 748 – 762
Most studies addressing biofilm formation in dental chair unit waterlines (DUWLs) have focused on a range of individual dental chair units (DCUs) and no studies on a centralised approach in a large number of DCUs have been reported to date.
Objectives: To develop a centralised, automated water quality and biofilm management system serving the distribution network providing water to Dublin Dental Hospital’s 103 DCUs, capable of maintaining DUWL supply and output water at better than potable quality standards in the long-term and requiring a minimum of human intervention. The potable water standard for the European Union does not specify an upper limit of aerobic hetero¬trophic bacteria, whereas a maximum of 100 cfu/mL is permitted in bottled water.
Methods: Mains water of varying quality was treated by specifically selected automated filtration units to provide DCUs with water of consistent chemical composition. This water was then automatically disinfected using an electrochemically activated solution EcasolTM (Trustwater Group, Clonmel, Ireland) (2.5 ppm) prior to distribution to DCUs. Microbiological quality of both DUWL supply and output water was monitored weekly by culture on R2A agar for 10 sentinel DCUs for a 100-week period. DUWLs were tested for the presence of biofilm by electron microscopy.
Results: Chemical composition of processed mains water consistently bettered potable water standards. DUWL supply water and output water aerobic heterotrophic bacterial counts averaged <1 and 18.1 cfu/mL, respectively, from the 10 DCUs, compared to 88 cfu/mL for unprocessed mains water. This correlated with the absence of biofilm in DUWLs. No adverse effects due to EcasolTM treatment of supply water were observed for DUWLs or DCU instruments.
Conclusions: This centralised and automated water treatment and biofilm management system consistently maintains DUWL output water at better than potable quality simultaneously in a large number of DCUs over the long-term.
M.J. O’Donnell et al. A novel automated waterline cleaning system that facilitates effective and consistent control of microbial biofilm contamination of dental chair unitwaterlines: A one-year study. JOURNAL O F DENTISTRY 34 (2006) 648 – 661
Microbial contamination of dental chair unit (DCU) output water caused by biofilm growth in dental unit waterlines (DUWs) is a universal problem and a potentially significant source of cross-infection. The microbial quality of output water from a Planmeca Compact i DCU equipped with the novel Water Management System (WMS), an integrated and automated DUW cleaning system, was investigated over a 12-month period with the hydrogen per¬oxide- and silver ion-containing disinfectants Planosil and Planosil Forte. Four weeks after connection to the potable-water quality mains supply the density of aerobic heterotrophic bacteria, rose from the low levels consistently found in the supply water throughout this study (mean average 77 cfu/mL) to 15,400 cfu/mL. Disinfection of DUWs once weekly with Planosil for 10 weeks resulted in a dramatic reduction in bacterial density immediately following disinfection (mean average 26 cfu/mL). Bacterial density rose steadily between disinfections and by 7 days post-disinfection, water quality failed (mean average 384 cfu/ mL) the American Dental Association DCU water quality standard of <200 cfu/mL. The DCU was then disinfected once weekly for 40 weeks with Planosil Forte. The average bacterial density immediately post-disinfection was 20 cfu/mL and 7 days post-disinfection was 113 cfu/mL. Electron microscopy showed that improved output water quality following disinfection with both disinfectants was associated with marked elimination of DUW biofilm, but deterioration of water quality following disinfection was associated with its regrowth. The most common bacterial species cultured from the mains water and the DCU output water were Microcococcus luteus and Sphingomonas spp., respectively, the latter of which are known opportunistic pathogens. The findings of this study show that the Planmeca Compact i DCU equipped with the easy to use and automated WMS, that requires minimal effort on the part of the operator, consistently provides output water that passes the ADA quality standard of <200 cfu/mL for up to 7 days following once-weekly disinfection with Planosil Forte.
M.J. O’Donnell et al. Bacterial contamination of dental chair units in a modern dental hospital caused by leakage from suction system hoses containing extensive biofilm. Journal of Hospital Infection (2005) 59, 348–360
Within six months of opening of the new Dublin Dental Hospital in September 1998, areas of corrosion were observed on many of the baseplates of the hospital’s 103 dental chair units (DCUs) at the site of attachment of the suction hoses. The corroded areas were heavily contaminated with Pseudomonas spp. and related genera posing a risk of cross-infection, particularly for immunocompromised patients. These species were used as marker organisms to investigate the source of the contamination. P. aeruginosa was the predominant species recovered from 41 selected DCU baseplates (61% prevalence), whereas P. putida (46% prevalence) and P. aeruginosa (43% prevalence) were predominant at the attachment ends of 37 selected high-volume suction hoses. Forty-one selected isolates of P. aeruginosa from 13 DCU baseplates, 16 high-volume suction hoses and 12 coarse filter housings (another suction system site) from 19 separate DCUs were serotyped to determine the similarity of isolates at each site. The majority of isolates (68.3%) belonged to serotype O:10, while the remainder belonged to serotypes O:6 (7.3%), O:11 (7.3%), O:14 (9.8%) and O:5/O:16 (7.3%). Of the isolates from DCU baseplates, additional isolates with the same serotype were recovered from other suction system sites in 10/13 (77%) cases. Isolates of only one serotype were recovered from each of the 19 DCUs investigated. Forty-one serotyped isolates were also subject to computer-assisted analysis of SpeI-generated DNA fingerprint profiles, and similarity coefficient (SABs) values were calculated for each pairwise combination of isolate profiles. The Data obtained showed that the isolates consisted of two distinct main populations, each containing separate clades corresponding to specific serotypes. Serotype O:6 (three isolates), O:11 (three isolates) and O:5/O:16 (three isolates) belonged to a single strain in each case. Serotypes O:14 (four isolates) and O:10 (28 isolates) belonged to two strains in each case. The two serotype O:10 strains, termed fingerprint groups I (four isolates from three DCUs) and II (24 isolates from 10 DCUs), were the most distantly related of all the strains identified. These findings demonstrated that the hospital DCUs had become colonized with a small number of P. aeruginosa strains, one of which (serotype O:10, fingerprint group II) predominated. These results also confirmed that DCU baseplate contamination was most likely to be due to leakage from suction system hoses at the baseplate attachment sites, probably due to loosening during use. Replacement hose connectors that firmly retained the suction hoses in the attachment sites so that they could not be loosened by movement of the suction hoses solved this problem, and eliminated further contamination of the DCU baseplates.
D.C. Coleman et al. Biofilm problems in dental unit water systems and its practical control. Journal of Applied Microbiology 106 (2009) 1424–1437
Dental chair units (DCUs) contain integrated systems that provide the instru¬ments and services for a wide range of dental procedures. DCUs use water to cool and irrigate DCU-supplied instruments and tooth surfaces during dental treatment. Water is supplied to these instruments by a network of intercon¬nected narrow-bore (2–3 mm) plastic tubes called dental unit waterlines (DUWLs). Many studies over the last 40 years demonstrated that DUWL out¬put water is often contaminated with high densities of micro-organisms, pre¬dominantly Gram-negative aerobic heterotropic environmental bacteria, including Legionella and Pseudomonas species. Untreated DUWLs host biofilms that permit micro-organisms to multiply and disperse through the water net¬work and which are aerosolized by DCU instrument use, thus exposing patients and staff to these micro-organisms, to fragments of biofilm and bacterial endo-toxins. This review concentrates on how practical developments and innova¬tions in specific areas can contribute to effective DUWL biofilm control. These include the use of effective DUWL treatment agents, improvements to DCU supply water quality, DCU design changes, development of automated DUWL treatment procedures that are effective at controlling biofilm in the long-term and require minimal human intervention, are safe for patients and staff, and which do not cause deterioration of DCU components following prolonged use.
M.A. Boyle eta l. Control of bacterial contamination of washbasin tapsand output water using Ecasol: a one-year study. Journal of Hospital Infection 80 (2012) 288-292
Background: Contaminated washbasin taps and output water are an important source of bacteria that may cause nosocomial infection. A five-week pretreatment study of hot and cold water from 15 washbasin taps at Dublin Dental Hospital showed consistently heavy contamination by aerobic heterotrophic bacteria: mean bacterial counts of 482.5 [standard deviation (SD) 293] colony-forming units (cfu)/mL and 5022 (SD 4322) cfu/mL, respectively. Aim: To minimize microbial contamination of washbasin taps and output water in the long term using the electrochemically generated, pH-neutral disinfectant, Ecasol.
Methods: Initially, the 15,000-L water tank providing cold and hot water to washbasins, calorifiers and the distribution network were drained and sediment was removed. The system was shock-dosed with Ecasol 100 ppm to eradicate gross contamination and biofilms. Thereafter, tank water was automatically maintained at Ecasol 2.5 ppm prior to distribution. The microbiological quality of water from five sentinel washbasin taps was monitored weekly for 54 weeks using R2A agar.
Findings: The mean counts for hot, cold, mains and tank water during the 54-week study period were 1 (SD 4) cfu/mL, 2 (SD 4) cfu/ml., 205 (SD 160) cfu/mL and 0 cfu/mL, respectively. Swab samples of 33/40 taps, each tested on three separate occasions, yielded no growth on R2A agar, while five samples yielded <20 cfu/swab and two samples yielded >200 cfu/swab. No detrimental effects due to Ecasol were observed in the water network. Conclusion: Ecasol consistently minimized bacterial contamination of washbasin taps and output water in a dental hospital setting.
M.A. Boyle et al. Lack of cytotoxicity by Trustwater EcasolTM used to maintain good quality dental unit waterline output water in keratinocyte monolayer and reconstituted human oral epithelial tissue models. JOURNAL O F DENTISTRY 38 ( 2010 ) 930 – 940
We previously showed that residual treatment of dental chair unit (DCU) supply water using the electrochemically-activated solution Trustwater EcasolTM (2.5 ppm) provided an effec¬tive long-term solution to the problem of dental unit waterline (DUWL) biofilm resulting in DUWL output water quality consistently superior to potable water.
Objectives: To investigate the cytoxicity of Ecasol using cultured keratinocyte monolayers and reconstituted human oral epithelial (RHE) tissue and to extend the study of Ecasol’s effectiveness in maintaining the microbiological quality of DUWL output water.
Methods: TR146 human keratinocyte monolayers and RHE tissues were exposed to Ecasol (2.5–100 ppm) for 1 h periods after removal of growth medium and washing with phosphate-buffered saline (PBS). Experiments were repeated using Ecasol that had been exposed for 30 min to 1–2 mg/mL bovine serum albumin (BSA), equivalent to protein concentrations in saliva. To quantitatively determine cytotoxic effects on monolayers following Ecasol expo¬sure, the Alamar Blue proliferation assay (assesses cell viability) and the Trypan Blue exclusion assay (assesses plasma membrane integrity), were used. Cytotoxicity effects on RHE tissues were assessed by the Alamar Blue assay and by histopathology.
Results: Ecasol at >5.0 ppm resulted in significant (P < 0.001) cytotoxicity to keratinocyte monolayers following a 1 h exposure. These effects, however, were completely negated by BSA pretreatment of Ecasol. No cytotoxicity was observed in the more complex RHE tissue at any of the Ecasol concentrations tested. In a 60-week study of 10 DCUs, tested weekly, the average density of aerobic heterotrophic bacteria in Ecasol-treated (2.5 ppm) DCU supply water was <1 cfu/mL and in DUWL output water was 6.5 cfu/mL.
Conclusions: Ecasol present as a residual disinfectant in DUWL output water is very unlikely to have adverse effects on human oral tissues at levels effective in maintaining DUWL output water quality at better than potable standard water quality.
M.J. O’Donnell et al. Management of dental unit waterline biofilms in the 21st century. Future Microbiol (2011) 6(10), 1209–1226
Dental chair units (DCUs) use water to cool and irrigate DCU-supplied instruments and tooth surfaces, and provide rinsewater during dental treatment. A complex network of interconnected plastic dental unit waterlines (DUWLs) supply water to these instruments. DUWLs are universally prone to microbial biofilm contamination seeded predominantly from microorganisms in supply water. Consequently, DUWL output water invariably becomes contaminated by high densities of microorganisms, principally Gram-negative environmental bacteria including Pseudomonas aeruginosa and Legionella species, but sometimes contain human-derived pathogens such as Staphylococcus aureus. Patients and staff are exposed to microorganisms from DUWL output water and to contaminated aerosols generated by DCU instruments. A wide variety of approaches, many unsuccessful, have been proposed to control DUWL biofilm. More recently, advances in biofilm science, chemical DUWL biofilm treatment agents, DCU design, supply water treatment and development of automated DUWL biofilm control systems have provided effective long-term solutions to DUWL biofilm control.