A centralised, automated dental hospital water quality and biofilm management system using neutral Ecasol™ maintains dental unit waterline output at better than potable quality: A 2-year longitudinal study

Electrolysed oxidising water as a multi-purpose biocide in dental healthcare-A scoping review

OBJECTIVES

The objective of this scoping review was to map evidence of electrolysed oxidising water (EOW) as a biocide for dental applications of relevance to older people and identify research gaps.

BACKGROUND

EOW is an emerging, "green," and cost-effective biocide. There are no reviews on the landscape of EOW research as either an antiseptic or disinfectant in dental healthcare or its suitability for the oral healthcare of older people.

MATERIALS AND METHODS

The review follows the PRISMA Extension for Scoping Reviews (PRISMA-ScR) guidelines. Database searches (Google Scholar, PubMed, Web of Science, Ovid, Scopus and Science Direct) were undertaken using MESH terms and Boolean operators with no date restrictions, to identify full-text, original reports published in English-language peer-reviewed journals.

RESULTS

The search yielded 114 papers that met the inclusion/exclusion criteria. Dental applications of EOW include its use as an endodontic irrigant (39%); mouth rinse/surgical irrigant (21%); disinfectant for dental unit water lines (19%) and dental biomaterials (17%); and for antimicrobial efficacy, effects on oral tissues and on dental material properties. Most studies (83%) evaluated a single EOW formulation (acidic, moderately acidic or neutral) that was either generated at 'point-of-use' (POU; 72%), bottled ('ready-to-use', RTU; 24%) or from unspecified (3%) sources. Six reports evaluated storage-related parameters and 25 evaluated clinical applications; 89 were in vitro studies and one investigated the cost-effectiveness of POU EOW.

CONCLUSIONS

Neutral-pH, EOW is effective as an antimicrobial agent without deleterious effects on oral tissues. However, research on the impact of storage conditions, anti-Candida biofilm efficacy and mechanism of action against yeasts, long-term effects on denture materials and cost-effectiveness is required to establish the suitability of EOW as a multipurpose biocide for dental healthcare, including infection-control requirements relating to older people.

Storage-related stability and antimicrobial efficacy of bottled, neutral-pH Electrolysed Oxidising Water

OBJECTIVES

Denture stomatitis is prevalent in older people and poses serious health risks. Ready-to-use (RTU) neutral-pH Electrolysed Oxidizing Water (EOW) is an effective environmental disinfectant used in residential care settings and geriatric wards. However, the influence of storage on stability and effectiveness for denture disinfection has not been established. This research investigated the storage-related stability and antimicrobial activity of RTU EOW, and its efficacy against Candida albicans biofilms formed on denture resin.

METHODS

The pH, oxidation/reduction potential (mV), available chlorine content (mg/L) and [HOCl] (mM) of RTU EOW (Envirolyte, New Zealand) solutions (n = 22) were measured from bottle opening to 28 days following storage at 4 °C, room temperature (RT) or 37 °C. Staphylococcus aureus and C. albicans cells were incubated in 80% EOW for contact times (CTs) up to 15 min and colony-forming units (cfu) determined. Minimum inhibitory concentrations (MIC90 EOW-HOCl) after CTs up to five minutes were determined for S. aureus and C. albicans reference strains and clinical isolates. C. albicans-denture resin disc biofilms were assessed after a five-minute CT with undiluted EOW by XTT-metabolic activity assay.

RESULTS

[HOCl] remained stable when RTU EOW was stored at 4 °C or RT for five months after manufacture. One-minute CT resulted in log10 cfu reductions of >6 for S. aureus and >5 for C. albicans. Mean MIC90 for five-minute CT was 37 µM (S. aureus) and 54 µM (C. albicans). Undiluted EOW reduced C. albicans biofilm metabolic activity by 86%.

CONCLUSIONS

RTU neutral-pH EOW is stable over five-months storage and is an effective denture disinfectant.

CLINICAL SIGNIFICANCE

The efficacy of the RTU neutral EOW against C. albicans isolates and biofilms formed on denture resin surfaces supports its use as a denture disinfectant and can inform future research to assess its potential for preventing denture-related oral Candida infections in the older population, especially in resource-limited communities.

Immersion of debrided diabetic foot ulcer (DFU) tissue in electrochemically generated pH neutral hypochlorous acid significantly reduces the microbial bioburden: whole-genome sequencing of Staphylococcus aureus, the most prevalent species recovered

BACKGROUND

Diabetic foot ulcer infections (DFUIs) are the leading cause of lower limb amputations, mediated predominantly by Staphylococcus aureus. pH neutral electrochemically-generated hypochlorous acid (anolyte) is a non-toxic, microbiocidal agent with significant potential for wound disinfection.

AIMS

To investigate both the effectiveness of anolyte for microbial bioburden reduction in debrided ulcer tissues and the population of resident S. aureus.

METHODS

Fifty-one debrided tissues from 30 people with type II diabetes were aliquoted by wet weight and immersed in 1 or 10 ml volumes of anolyte (200 parts per million) or saline for three min. Microbial loads recovered were determined in colony forming units/g (CFU/g) of tissue following aerobic, anaerobic and staphylococcal-selective culture. Bacterial species were identified and 50 S. aureus isolates from 30 tissues underwent whole-genome sequencing (WGS).

FINDINGS

The ulcers were predominantly superficial, lacking signs of infection (39/51, 76.5%). Of the 42/51 saline-treated tissues yielding ≥10⁵ CFU/g, a microbial threshold reported to impede wound-healing, only 4/42 (9.5%) were clinically-diagnosed DFUIs. Microbial loads from anolyte-treated tissues were significantly lower than saline-treated tissues using 1 ml (1065-fold, 2.0 log) and 10 ml (8216-fold, 2.1 log) immersion volumes (p<0.0005). Staphylococcus aureus was the predominant species recovered (44/51, 86.3%) and 50 isolates underwent WGS. All were meticillin-susceptible and comprised 12 sequence types (STs), predominantly ST1, ST5 and ST15. Whole-genome multilocus sequence typing identified three clusters of closely related isolates from 10 patients indicating inter-patient transmission.

CONCLUSIONS

Short immersions of debrided ulcer tissue in anolyte significantly reduced microbial bioburden: a potential novel DFUI treatment.

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

BACKGROUNDS

Numerous studies have shown that dental unit water lines (DUWLs) are often contaminated by a wide range of micro-organisms (bacteria, fungi, protozoa) and various prevalence have been reported for it in previous studies. Therefore, this review study aims to describe the prevalence of bacterial biofilm contamination of DUWLs.

METHODS

This is a systematic review and meta-analysis in which the related keywords in different international databases, including Medline (via PubMed) and Scopus were searched. The retrieved studies were screened and the required data were extracted from the included studies. Three standard methods including American Dental Association (ADA), The Center for Disease Control and Prevention (CDC) and contaminated > 100 CFU/ml(C-100) standards were used to assess the bacterial biofilm contamination of DUWLs. All studies that calculated the prevalence of bacterial biofilm contamination of DUWLs, and English full-text studies were included in the meta-analysis. Studies that did not have relevant data or used unusual laboratory methods were excluded. Methodological risk of bias was assessed by a related checklist and finally, the data were pooled by fixed or random-effect models.

RESULTS

Seven hundred and thirty-six studies were identified and screened and 26 related studies were included in the meta-analysis. The oldest included study was published in 1976 and the most recent study was published in 2020. According to the ADA, CDC and C-100 standards, the prevalence of bacterial contamination was estimated to be 85.0% (95% confidence interval (CI): 66.0-94.0%), 77.0% (95%CI: 66.0-85.0%) and 69.0% (95%CI: 67.0-71.0%), respectively. The prevalence of Legionella Pneumophila and Pseudomonas Aeruginosa in DUWLs was estimated to be 12.0% (95%CI: 10.0-14.0%) and 8.0% (95%CI: 2.0-24.0%), respectively.

CONCLUSION

The results of this review study suggested a high prevalence of bacterial biofilm in DUWLs; therefore, the use of appropriate disinfecting protocol is recommended to reduce the prevalence of contamination and reduce the probable cross-infection.

Electrolyzed Water Generated On-Site as a Promising Disinfectant in the Dental Office During the COVID-19 Pandemic

Electrolyzed water is a safe, broad-spectrum bactericidal and viricidal agent, which can be used as a potent and effective alternative disinfectant in case of supply shortages. This report describes the on-site production of slightly acidic electrolyzed water (EW) from diluted salt solution and vinegar at a dental office using a portable EW generator unit. Such measures can ensure the safe continuity of important dental service provision for our patients during the coronavirus disease 2019 (CoVID-19) pandemic.

Chlorine-based DUWL disinfectant leads to a different microbial composition of water derived biofilms compared to H2O2-based chemical disinfectants in vitro

Background

Biofilm formation in dental unit waterlines (DUWL) may lead to health risks for dental staff and patients. Therefore, dental unit waterlines need to be disinfected, for instance by using chemical disinfectants. However, the application of chemical disinfectants may lead to the selection of specific microorganisms. Therefore, the aim of our study was to assess the microbial composition of water-derived biofilms, after a continuous exposure to maintenance doses of commercially available chemical disinfectants, in vitro.

Methods

The AAA-model was used to grow water derived biofilms. The biofilms were subjected to the maintenance dose of each disinfectant. To determine the microbial composition, the V4 hypervariable region of the 16S rRNA gene was sequenced. The sequences were clustered in operational taxonomic units (OTUs).

Results

The bacterial composition of biofilms in all treatment groups differed significantly (PERMANOVA F = 4.441, p = 0.001). Pairwise comparisons revealed Anoxyl treated biofilms were significantly different from all groups (p = 0.0001). In the Anoxyl-treated biofilms, the relative abundance of Comamonadaceae and Sphingopyxis was high compared to the Dentosept, Green and Clean and Oxygenal groups.

Conclusion

We concluded that exposure to low doses of the chlorine-based chemical disinfectant Anoxyl led to a substantially different composition of water derived biofilms compared to biofilms exposed to H₂O₂-based chemical disinfectants.

Whole-genome sequencing identifies highly related Pseudomonas aeruginosa strains in multiple washbasin U-bends at several locations in one hospital: evidence for trafficking of potential pathogens via wastewater pipes

BACKGROUND

Hand washbasin U-bends have increasingly been associated with nosocomial outbreaks by Gram-negative bacteria, including Pseudomonas aeruginosa which is virtually ubiquitous in U-bends. Wastewater networks servicing U-bends are potential highways for trafficking pathogenic bacteria.

AIM

To use P. aeruginosa to investigate trafficking of bacteria between hospital washbasin U-bends.

METHODS

Twenty-five washbasin U-bends in five locations in Dublin Dental University Hospital (DDUH) were investigated for trafficking of P. aeruginosa: 10 in Clinic 2 (C2), 10 in the Accident & Emergency Department (A&E) and five in three other locations. In addition, washbasin tap samples (N=80) and mains and tap water samples (N=72) were cultured for P. aeruginosa. Selected P. aeruginosa isolates recovered over 29 months underwent whole-genome sequencing, and relatedness was interpreted using whole-genome multi-locus sequence typing and pairwise single nucleotide polymorphism (SNP) analysis.

FINDINGS

P. aeruginosa was recovered from all U-bends but not from taps or water. Eighty-three U-bend isolates yielded 10 sequence types (STs), with ST560 and ST179 from A&E, C2 and two other locations predominating (70%). ST560 was also recovered from a common downstream pipe. Isolates within ST560 and ST179 were highly related regardless of source. ST560 was divided into Cluster I (N=25) and Cluster II (N=2) with average allelic differences and SNPs of three and zero, and two and five, respectively. The 31 ST179 isolates exhibited an average allelic difference and SNPs of three and 12, respectively.

CONCLUSION

Highly related P. aeruginosa strains were identified in multiple U-bends in several DDUH locations, indicating trafficking via the wastewater network.

Minimizing microbial contamination risk simultaneously from multiple hospital washbasins by automated cleaning and disinfection of U-bends with electrochemically activated solutions

BACKGROUND

Outbreaks of infection associated with microbial biofilm in hospital hand washbasin U-bends are being reported increasingly. In a previous study, the efficacy of a prototype automated U-bend decontamination method was demonstrated for a single non-hospital pattern washbasin. It used two electrochemically activated solutions (ECA) generated from brine: catholyte with detergent properties and anolyte with disinfectant properties.

AIM

To develop and test a large-scale automated ECA treatment system to decontaminate 10 hospital pattern washbasin U-bends simultaneously in a busy hospital clinic.

METHODS

A programmable system was developed whereby the washbasin drain outlets, U-bends and proximal wastewater pipework automatically underwent 10-min treatments with catholyte followed by anolyte, three times weekly, over five months. Six untreated washbasins served as controls. Quantitative bacterial counts from U-bends were determined on Columbia blood agar, Reasoner's 2A agar and Pseudomonas aeruginosa selective agar following treatment and 24 h later.

FINDINGS

The average bacterial densities in colony-forming units/swab from treated U-bends showed a >3 log reduction compared with controls, and reductions were highly significant (P<0.0001) on all media. There was no significant increase in average bacterial counts from treated U-bends 24 h later on all media (P>0.1). P. aeruginosa was the most prevalent organism recovered throughout the study. Internal examination of untreated U-bends using electron microscopy showed dense biofilm extending to the washbasin drain outlet junction, whereas treated U-bends were free from biofilm.

CONCLUSION

Simultaneous automated treatment of multiple hospital washbasin U-bends with ECA consistently minimizes microbial contamination and thus the associated risk of infection.

Elimination of biofilm and microbial contamination reservoirs in hospital washbasin U-bends by automated cleaning and disinfection with electrochemically activated solutions

BACKGROUND

Washbasin U-bends are reservoirs of microbial contamination in healthcare environments. U-Bends are constantly full of water and harbour microbial biofilm.

AIM

To develop an effective automated cleaning and disinfection system for U-bends using two solutions generated by electrochemical activation of brine including the disinfectant anolyte (predominantly hypochlorous acid) and catholyte (predominantly sodium hydroxide) with detergent properties.

METHODS

Initially three washbasin U-bends were manually filled with catholyte followed by anolyte for 5min each once weekly for five weeks. A programmable system was then developed with one washbasin that automated this process. This U-bend had three cycles of 5min catholyte followed by 5min anolyte treatment per week for three months. Quantitative bacterial counts from treated and control U-bends were determined on blood agar (CBA), R2A, PAS, and PA agars following automated treatment and on CBA and R2A following manual treatment.

FINDINGS

The average bacterial density from untreated U-bends throughout the study was >1×10(5) cfu/swab on all media with Pseudomonas aeruginosa accounting for ∼50% of counts. Manual U-bend electrochemically activated (ECA) solution treatment reduced counts significantly (<100cfu/swab) (P<0.01 for CBA; P<0.005 for R2A). Similarly, counts from the automated ECA-treatment U-bend were significantly reduced with average counts for 35 cycles on CBA, R2A, PAS, and PA of 2.1±4.5 (P<0.0001), 13.1±30.1 (P<0.05), 0.7±2.8 (P<0.001), and 0 (P<0.05) cfu/swab, respectively. P. aeruginosa was eliminated from all treated U-bends.

CONCLUSION

Automated ECA treatment of washbasin U-bends consistently minimizes microbial contamination.

Overcoming the problem of residual microbial contamination in dental suction units left by conventional disinfection using novel single component suction handpieces in combination with automated flood disinfection

OBJECTIVES

Decontaminating dental chair unit (DCU) suction systems in a convenient, safe and effective manner is problematic. This study aimed to identify and quantify the extent of the problems using 25 DCUs, methodically eliminate these problems and develop an efficient approach for reliable, effective, automated disinfection.

METHODS

DCU suction system residual contamination by environmental and human-derived bacteria was evaluated by microbiological culture following standard aspiration disinfection with a quaternary ammonium disinfectant or alternatively, a novel flooding approach to disinfection. Disinfection of multicomponent suction handpieces, assembled and disassembled, was also studied. A prototype manual and a novel automated Suction Tube Cleaning System (STCS) were developed and tested, as were novel single component suction handpieces.

RESULTS

Standard aspiration disinfection consistently failed to decontaminate DCU suction systems effectively. Semi-confluent bacterial growth (101-500 colony forming units (CFU) per culture plate) was recovered from up to 60% of suction filter housings and from up to 19% of high and 37% of low volume suction hoses. Manual and automated flood disinfection of DCU suction systems reduced this dramatically (ranges for filter cage and high and low volume hoses of 0-22, 0-16 and 0-14CFU/plate, respectively) (P<0.0001). Multicomponent suction handpieces could not be adequately disinfected without prior removal and disassembly. Novel single component handpieces, allowed their effective disinfection in situ using the STCS, which virtually eliminated contamination from the entire suction system.

CONCLUSION

Flood disinfection of DCU suction systems and single component handpieces radically improves disinfection efficacy and considerably reduces potential cross-infection and cross-contamination risks.

CLINICAL SIGNIFICANCE

DCU suction systems become heavily contaminated during use. Conventional disinfection does not adequately control this. Furthermore, multicomponent suction handpieces cannot be adequately disinfected without disassembly, which is costly in time, staff and resources. The automated STCS DCU suction disinfection system used with single component handpieces provides an effective solution.

Antiviral activity of Ecasol against feline calicivirus, a surrogate of human norovirus

Human norovirus (NoV) is a major cause of acute gastroenteritis in closed settings such as hospitals, hotels and cruise ships. The virus survives on inanimate surfaces for extended periods of time, and environmental contamination has been implicated in its transmission. The disinfection of contaminated areas is important in controlling the spread of NoV infections. Neutral solutions of electrochemically activated (ECA)-anolyte have been shown to be powerful disinfectants against a broad range of bacterial pathogens. The active chemical ingredient is hypochlorous acid (HOCl), which is registered as an approved food contact surface sanitizer in the United States by the Environmental Protection Agency, pursuant to 40 CFR 180.940. We evaluated the antiviral activity of Ecasol (an ECA-anolyte) against feline calicivirus (FCV), a surrogate of NoV. FCV dried on plastic surfaces was exposed to Ecasol for 1, 2, or 5min. After exposure to Ecasol, the virus titers were compared with untreated controls to determine the virus inactivation efficacy after different contact times. Ecasol was found to decrease the FCV titer by >5log(10) within 1min of contact, indicating its suitability for inactivation of NoV on surfaces.

Update on infectious risks associated with dental unit waterlines

Modern dental chair units consist of a network of interconnected narrow-bore plastic tubes called dental unit waterlines (DUWLs). The water delivered by these DUWLs acts as both a coolant for a range of instruments and an irrigant during dental treatments. The quality of water is of considerable importance because both patients and dental team are regularly exposed to water and aerosols generated by dental equipment. Studies have demonstrated that DUWLs provide a favourable environment for microbial proliferation and biofilm formation, and that water is consequently often contaminated with high densities of various microorganisms (bacteria, fungi, protozoa, viruses). The presence of high levels of microbial contamination may be a health problem for dentists and patients, especially those who are immunocompromised. The current status of knowledge on microbial contamination of DUWLs is presented, with an emphasis on the infectious risk associated with DUWLs and on the various approaches for disinfecting and protecting DUWLs.

Management of dental unit waterline biofilms in the 21st century

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.

Microbial biofilm control within the dental clinic: reducing multiple risks

This short review focuses on biofilms in the dental clinic environment. Microbial biofilms are potentially a significant source of cross-contamination and cross-infection in the dental clinic. Biofilms in dental chair unit waterlines (DUWLs), suction hoses and fittings pose the most significant risk as these may come into contact with the patient during treatment. These can be managed effectively by regular disinfection using chemical disinfectants and procedures that have proven efficacy. As dental chair units (DCUs) are classified as medical devices, there is a requirement for DCU manufacturers to provide detailed guidance for their decontamination. Planned routine preventive maintenance of the dental clinic water network and good quality water will considerably minimise infection risks from microorganisms in tap water and has benefits for the operation of other clinic equipment. Regular and effective cleaning and disinfection of taps, sinks and splash-backs will help to minimise reservoirs and disseminators of potentially pathogenic bacteria from these areas.