Bacterial biofilm prevalence in dental unit waterlines: a systematic review and meta-analysis

Dental unit waterline infection control practice and knowledge gaps

BACKGROUND

Dental unit waterline (DWL) infection control is critical to infection prevention. Identifying challenges and barriers to its implementation is a first step toward understanding how to improve engagement.

METHODS

A survey was distributed to dentists, dental hygienists, and dental assistants via the Qualtrics XM platform (Qualtrics). Responses were analyzed to quantify engagement in practices contrary to Centers for Disease Control and Prevention guidance and identify avenues to improve engagement.

RESULTS

Although oral health care providers recognized DWL infection control was important, there was a lack of clarity about appropriate routine engagement (eg, what lines should be tested), what should be noted in practice infection control records, and steps to be taken in response to a failed test result (ie, ≥ 500 colony-forming units/mL), such as taking a chair out of service.

CONCLUSIONS

Survey results showed there were considerable gaps in knowledge and practice that could lead to patient harm. Oral health care provider training may not prepare personnel adequately to engage in, let alone supervise, DWL infection control. DWL infection control, like other aspects of infection control, requires action informed via an understanding of what needs to be done. Although good intentions are appreciated, better approaches to DWL infection control information dissemination and strategies to engage dental assistants, dental hygienists, and dentists in best practices are needed.

PRACTICAL IMPLICATIONS

Evolving standards of care, including infection control, should be reflected in the provision of dental treatment. Improvements in communicating and ensuring engagement in best practices are needed when it comes to DWL infection control.

Comparing the Effects of Two Culture Methods to Determine the Total Heterotrophic Bacterial Colony Count in Hospital Purified Water

BACKGROUND

Accurately detecting the quantity of microorganisms in hospital purified water is of significant importance for early identification of microbial contamination and reducing the occurrence of water-borne hospital infections. The choice of detection method is a prerequisite for ensuring accurate results. Traditional Plate Count Agar (PCA) belongs to a high-nutrient medium, and there may be limitations in terms of accuracy or sensitivity in detecting microorganisms in hospital purified water. On the other hand, Reasoner's 2A agar (R2A) has characteristics, such as low-nutrient levels, low cultivation temperature, and extended incubation time, providing advantages in promoting the growth of aquatic microorganisms. This study, through comparing the differences in total colony counts between two detection methods, aims to select the method more suitable for the growth of aquatic microorganisms, offering new practical insights for accurately detecting the total count of heterotrophic bacteria in hospital purified water.

METHODS

The most commonly used plate count agar (PCA) method, and the R2A agar culture were adopted to detect microorganisms and determine the total number of bacterial colonies in the water for oral diagnosis and treatment water and terminal rinse water for endoscopes in medical institutions. The two water samples were inoculated by pour plate and membrane filtration methods, respectively. Using statistical methods including Spearman and Pearson correlation, Wilcoxon signed-rank sum test, paired-Chi-square test, and linear regression, we analyze the differences and associations in the bacterial counts cultivated through two different methods.

RESULTS

In 142 specimens of the water, the median and interquartile range of the heterotrophic bacterial colony number under the R2A culture method and under the PCA culture method were 200 (Q1-Q3: 25-18,000) and 6 (Q1-Q3: 0-3700). The total number of heterotrophic bacteria colonies cultured in R2A medium for 7 days was more than that cultured in PCA medium for 2 days (P < 0.05). The linear regression results showed a relatively strong linear correlation between the number of colonies cultured by the R2A method and that cultured by the PCA method (R2 = 0.7264). The number of bacterial species detected on R2A agar medium is greater than that on PCA agar medium.

CONCLUSION

The R2A culture method can better reflect the actual number of heterotrophic bacterial colonies in hospital purified water. After logarithmic transformation, the number of colonies cultured by the two methods showed a linear correlation.

The importance of biofilm contamination control for dental unit waterlines: a multicenter assessment of the microbiota diversity of biofilm in dental unit waterlines

Background

The biofilm formation in Dental Unit Waterlines (DUWLs) could become an important cause of infection during dental care, which could put immunocompromised individuals at risk of cross-infection. The aim of this study was to characterize the microbial communities of biofilms among DUWLs using high-throughput sequencing technology.

Methods

Twenty-nine biofilm samples were obtained from 24 dental chair units at 5 hospitals and 2 dental clinics. The genomic DNA of the samples was extracted, then 16S rDNA and ITS2 gene were amplified and sequenced. Alpha-diversity and Beta-diversity were calculated with QIIME2 and the Kruskal - Wallis H-test was adopted for statistical analysis.

Results

Microbial communities with a high diversity of bacteria (377 genera) and fungi (83 genera) were detected in the biofilm samples. The dominant phylum of bacteria was Proteobacteria (93.27%) and that of fungi was Basidiomycota (68.15%). Potential human pathogens were detected including 7 genera of bacteria (Pseudomonas, Stenotrophomonas, Hafnia-Obesumbacterium, Burkholderia-Caballeronia-Paraburkholderia, Ralstonia, Enterobacter, Klebsiella) and 6 genera of fungi (Malassezia, Candida, Alternaria, Cryptococcus, Rhodotorula, Rhinocladiella).

Conclusions

This multicenter assessment revealed the infectious risk during dental care. It emphasized the importance of biofilm control due to biofilm accumulation and multiple kinds of opportunistic pathogens in DUWLs.

Dental unit waterline testing practices: an 11-Year retrospective study

OBJECTIVES

This retrospective study examined the dental unit waterline (DUWL) testing practices of Saskatchewan dental clinics over a period of 11 years, with an emphasis on their responses after identification of high microbial levels.

MATERIALS AND METHODS

Dental clinics (n = 137) aseptically collected samples of output water from their air/water syringes, handpieces, and ultrasonic scaler lines using Sigma-Aldrich® waterline test kits and delivered them to a quality assurance laboratory. Tests were incubated for seven days at room temperature, and those with heterotrophic plate counts > 500 CFU/mL were reported as failures. Statistical analyses were performed on a database containing 4,093 test results.

RESULTS

Participating clinics submitted an average of 11 DUWL tests per year. Overall, 21% of tests failed, and a moderate positive association (rs=.52, p < 0.001) was found between clinics' DUWL testing frequency and failure rate. Only 7% of failed DUWL tests were followed up by collection of a subsequent test within two weeks, of which 47% still exceeded the 500 CFU/mL threshold.

CONCLUSIONS

Our findings demonstrate an association between DUWL testing frequency and detection of unacceptable microbial levels, along with infrequent retesting and often-inadequate intervention after a failed test. This suggests the need for further efforts at the regulatory and educational levels to maintain adequate water quality during dental treatment.

CLINICAL RELEVANCE

Procedural water can become contaminated in DUWLs and endanger patients. Regular DUWL monitoring and evidence-based interventions to treat contaminated systems are necessary to safeguard patient health.

Comparative evaluation of effect of sodium hypochlorite and chlorhexidine in dental unit waterline on aerosolized bacteria generated during dental treatment

BACKGROUND

In dentistry, nosocomial infection poses a great challenge to clinicians. The microbial contamination of water in dental unit waterlines (DUWLs) is ubiquitous. Such infected DUWLs can transmit oral microbes in the form of aerosols. Previous studies have suggested treating DUWLs with various disinfectants to reduce cross-contamination. The literature lacks a comparative evaluation of the effect of the use of 0.2% chlorhexidine (CHX) and 0.1% sodium hypochlorite (NaOCl) in DUWLs on aerosolized bacteria generated during dental procedures.

OBJECTIVE

To compare the effect of NaOCl and CHX in DUWLs on aerosolized bacteria generated during restorative and endodontic procedures.

MATERIALS AND METHODS

A total of 132 patients were equally divided into three groups (n = 44 in each group) according to the content of DUWL as follows. Group I-0.1% NaOCl Group II-0.2% CHX Group III-distilled water (Positive control) One-way ANOVA was performed and the Kruskal-Wallis test was used for intergroup comparison.

RESULTS

For the restorative procedure, inter-group comparison of mean colony-forming units (CFU) scores showed a statistically significant difference between the groups (p - .001) with the score of group 3 higher than group 2 followed by group 1. For the endodontics, an inter-group comparison of CFU scores showed a statistically significant difference between the groups (p - .003) with the mean score in group 1 being the lowest and group 3 being the highest.

CONCLUSION

The addition of NaOCl or CHX in DUWLs shows an effective reduction in aerosolized bacteria compared to distilled water.

Legionella pneumophila Presence in Dental Unit Waterlines: A Cultural and Molecular Investigation in the West Bank, Palestine

A Legionella pneumophila bacterium is ubiquitous in water distribution systems, including dental unit waterlines (DUWLs). Legionellosis is atypical pneumonia, including Legionnaires' disease (LD) and the less acute form of Pontiac fever. Legionellosis occurs as a result of inhalation/aspiration of aerosolized Legionella-contaminated water by susceptible patients, health workers, and dentists. In this study, we undertook to determine the prevalence of Legionella in water and biofilm samples from Tap and DUWLs collected from five sites of dental clinics and faculties across the West Bank. Water samples were tested for physical and chemical parameters. The study samples included 185 samples, 89 (48%) water samples, and 96 (52%) biofilm swabs, which were analyzed by cultivation-dependent analysis (CDA) and by the cultivation-independent technique (CIA). Also, partial sequencing of the 16S rRNA gene for fifteen L. pneumophila isolates was performed for quality assurance and identification. L. pneumophila was isolated from 28 (15%) of 185 samples using CDA and was detected in 142 (77%) of 185 samples using CIA. The abundance of culturable L. pneumophila was low in DUWL of the sampling sites (range: 27-115 CFU/Liter). PCR was 5× more sensitive than the culture technique. L. pneumophila Sg 1 was detected in (75%) of the isolates, while (25%) isolates were L. pneumophila Sg 2-14. All fifteen sequenced Legionella isolates were identified as L. pneumophila ≥ 94.5%. The analysis of phylogenetic tree showed that L. pneumophila branch clearly identified and distinguished from other branches. These results show that DUWLs of the examined dental clinics and faculties are contaminated with L. pneumophila. This finding reveals a serious potential health risk for infection of immunocompromised patients and dentists' post-exposure.

The long-term effect of sub-boiling water on dental unit waterlines and its ability to control cross-contamination in dentistry

This study investigated the effect of water at high temperature on the physical and mechanical properties of polyurethane and on biofilm removal, aiming for its applicability in dental unit waterlines. The evaluations were carried out after simulating a 1-year period of daily immersion and measured changes in color, microhardness, surface roughness, and tensile strength before and after reproducing a disinfection protocol. For antibiofilm activity measurement, fragments of waterline were contaminated with Pseudomonas aeruginosa and submitted to the disinfection protocols. Relative to effects on the physical and mechanical properties, immersion in water at 60°C did not promote changes in color and tensile strength. However, lower values were observed for microhardness and increased values for surface roughness. Regarding antibiofilm action, water at 60°C significantly reduced the microbial load and promoted substantial changes in cells morphology. In conclusion, disinfection with water at 60°C demonstrated possible application in controlling cross-contamination in dentistry.

Effectiveness of iodine for continuous decontamination of dental unit waterline

OBJECTIVE

Dental Unit Waterlines (DUWLs) are contaminated by various species of microorganisms. DUWLs should be disinfected appropriately to control microbial contamination. This study investigated the effectiveness of devices continuously releasing iodine to control microbial contamination in DUWLs.

MATERIALS AND METHODS

Ten dental chair units (DCU) at Chulalongkorn University were randomized into the iodine and control groups. After setting iodine treatment devices, the DCU was allowed to operate normally. 25 ml of water from airotors lines were collected weekly for enumerating bacteria. The viability of biofilms in DUWLs was quantified by ATP testing kit. The amount of iodine released into the procedural water was also quantified.

RESULTS

The continuous presence of iodine could significantly control bacterial contamination in the DUWL to be less than 500 CFU/mL, the standard level recommended by the Centre for Disease Control and Prevention (CDC). Iodine treatment can reduce bacterial CFU up to 98-100%. Biofilm viability in the iodine group was slightly lower than that of the control group though not statistically significant. After eleven months, the average iodine release was measured to be 3.6 ppm which is still effective in controlling bacterial contamination.

CONCLUSION

Continuously supplying iodine in DUWLs effectively controls microbial contamination.