Biofilms In Dental Unit Water Lines Research Articles

QAPI 144 - Multiprong Interventions, Organizational Behavioral Changes, and Ongoing Monitoring Reduce Dental Unit Water Line Biofilm Growth

QAPI 144 - Multiprong Interventions, Organizational Behavioral Changes, and Ongoing Monitoring Reduce Dental Unit Water Line Biofilm Growth

Study on the disinfection effect of chlorine dioxide disinfectant (ClO2) on dental unit waterlines and its in vitro safety evaluation

BackgroundEnsuring the safety of dental unit waterlines (DUWLs) has become a pivotal issue in dental care practices, focusing on the health implications for both patients and healthcare providers. The inherent structure and usage conditions of DUWLs contribute to the risk of biofilm formation and bacterial growth, highlighting the need for effective disinfection solutions.The quest for a disinfection method that is both safe for clinical use and effective against pathogens such as Staphylococcus aureus and Escherichia coli in DUWLs underscores the urgency of this research.MaterialsChlorine dioxide disinfectants at concentrations of 5, 20, and 80 mg/L were used to treat biofilms of S. aureus and E. coli cultured in DUWLs. The disinfection effectiveness was assessed through bacterial counts and culturing. Simultaneously, human skin fibroblast cells were treated with the disinfectant to observe changes in cell morphology and cytotoxicity. Additionally, the study included corrosion tests on various metals (carbon steel, brass, stainless steel, aluminum, etc.).ResultsExperimental results showed that chlorine dioxide disinfectants at concentrations of 20 mg/L and 80 mg/L significantly reduced the bacterial count of S. aureus and E. coli, indicating effective disinfection. In terms of cytotoxicity, higher concentrations were more harmful to cellular safety, but even at 80 mg/L, the cytotoxicity of chlorine dioxide remained within controllable limits. Corrosion tests revealed that chlorine dioxide disinfectants had a certain corrosive effect on carbon steel and brass, and the degree of corrosion increased with the concentration of the disinfectant.ConclusionAfter thorough research, we recommend using chlorine dioxide disinfectant at a concentration of 20 mg/L for significantly reducing bacterial biofilms in dental unit waterlines (DUWLs). This concentration also ensures satisfactory cell safety and metal corrosion resistance.

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

BackgroundsNumerous 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.MethodsThis 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.ResultsSeven 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.ConclusionThe 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.

Protocol with non-toxic chemicals to control biofilm in dental unit waterlines: physical, chemical, mechanical and biological perspective

Biosafety in dentistry aims to combat cross-contamination and biofilm in dental unit waterlines. The aim was to investigate from a physical, chemical, mechanical and biological perspective, a protocol for using chemical products (citric acid, sodium bicarbonate and sodium chloride) to improve and maintain water quality in dental unit waterlines. Change in microhardness and corrosion tendency were observed in stainless steel samples. On the polyurethane surfaces, there were changes in color, microhardness and roughness. Anti-biofilm evaluations revealed a significant reduction in the biofilm biomass, metabolic activity and residual biofilm. These findings suggest that the protocol analyzed in this study showed an innovative potential against biofilm in dental unit waterlines, preserving the physical, chemical and mechanical properties of the materials.

Prevalence of E. coli and Coliform bacteria in the Dental Unit Waterlines of Private Clinics of Islamabad and Rawalpindi

Bacteria colonizing surfaces and forming biofilm in dental unit waterlines is a well-documented phenomenon. Pathogenic bacteria from contaminated dental unit water lines are transmitted with aerosols and splatter generated during dental procedures. Objective: To identify the presence of coliform bacteria and E. Coli in dental unit waterlines of private dental clinics in Islamabad and Rawalpindi to see whether they meet the criteria for drinking water. Methods: This is a quantitative study carried out on 30 active dental units. Triple syringe and handpiece outlet water samples were taken. Samples were evaluated by National Institute of Health (NIH) through Polymerase Chain Reaction (PCR). The cultures were incubated twice at 24 and 48 hours. The presence of coliform bacteria and E. coli in the samples was evaluated. Results: Approximately 20% of the samples were found to have coliform bacteria and E. coli. Some private dental clinics in Islamabad and Rawalpindi use dental unit waterlines that do not meet the criteria for drinking water. Conclusions: Dental unit water lines (DUWLs) must meet the set criteria for drinking water to reduce the risk of infections. Contamination with coliform bacteria and E. Coli were evident in some of the dental clinics. This contamination can be reduced by following Center for Disease Control (CDC) guidelines and using chemical treatment protocols for cleaning dental unit waterlines.

The Application of Silver to Decontaminate Dental Unit Waterlines-a Systematic Review.

The contamination of dental unit waterlines (DUWLs) is a major health concern since it can pose cross-infection risks among dental professionals and their patients. Silver is one of the widely used metals in medical fields due to its superior antimicrobial properties. Silver-based agents have been commercially available for the decontamination of dental unit water currently. This systematic review aims to examine the evidence supporting efficacy and safety of application of silver to decontaminate DUWLs. We performed a search of the peer-review literature of studies in six electronic databases using corresponding search terms. Eligibility was restricted to English-language studies exploring the application of silver to decontaminate dental unit water, e.g., silver-based disinfectants and silver-coated dental waterlines tubing. The search identified 148 articles, and 9 articles that met the criteria were synthesized with qualitative narrative analyses. We observed good evidence of antimicrobial efficacy of silver with hydrogen peroxide on diverse microorganism present in DUWLs. Furthermore, there is insufficient evidence on the application of silver nanoparticles (AgNPs) as an efficient material to control the biofilms in DUWLs. Post-treatment data of either the bactericidal and bacteriostatic effects of silver or AgNPs, especially the actual clinical efficacy of long-term application, are scarce. More high-quality research is needed to resolve the gap on the optimal dosage and treatment options required to control bacterial and biofilm in DUWLs with silver-containing materials.

Distinct Microbial Community of Accumulated Biofilm in Dental Unit Waterlines of Different Specialties.

The contamination of dental unit waterlines (DUWLs) is a serious problem and directly affects the dental care. This study aims to explore the microbial community of biofilm in DUWL from different specialties and investigate the associated factors. A total of 36 biofilm samples from 18 DUWL of six specialties (i.e., prosthodontics, orthodontics, pediatrics, endodontics, oral surgery, and periodontics) at two time points (i.e., before and after daily dental practice) were collected with a novel method. Genomic DNA of samples was extracted, and then 16S ribosomal DNA (rDNA) (V3–V4 regions) and ITS2 gene were amplified and sequenced. Kruskal–Wallis and Wilcoxon rank test were adopted for statistical analysis. Microbial community with high diversity of bacteria (631 genera), fungi (193 genera), and viridiplantae was detected in the biofilm samples. Proteobacteria was the dominant bacteria (representing over 65.74–95.98% of the total sequences), and the dominant fungi was Ascomycota (93.9–99.3%). Microorganisms belonging to multiple genera involved in human diseases were detected including 25 genera of bacteria and eight genera of fungi, with relative abundance of six genera over 1% (i.e., Acinetobacter, Pseudomonas, Enterobacter, Aspergillus, Candida, and Penicillium). The biofilm microbiome may be influenced by the characteristics of dental specialty and routine work to some extent. The age of dental chair unit and overall number of patients had the strongest impact on the overall bacteria composition, and the effect of daily dental practices (associated with number of patients and dental specialty) on the fungi composition was the greatest. For the first time, biofilm in DUWL related to dental specialty was comprehensively evaluated, with more abundance of bacterial and fungal communities than in water samples. Biofilm accumulation with daily work and multiple kinds of opportunistic pathogen emphasized the infectious risk with dental care and the importance of biofilm control.

Efficacy of BRS® and Alpron®/Bilpron® Disinfectants for Dental Unit Waterlines: A Six-Year Study.

Biofilms in dental unit waterlines (DUWL) are a potentially significant source of contamination posing a significant health risk as these may come into contact with patients and dental staff during treatment. The aim of this study was to evaluate the microbiological quality of DUWL water treated by Biofilm-Removing-System® (BRS®) and Alpron®/Bilpron® disinfectant solutions for six years in a French university hospital. The microbiological quality of water supplied by 68 dental units—initially shock treated with BRS®, then continuously treated by Alpron® with sterile water during working days and Bilpron® during inactivity period, and combined with purging every morning and after each patient—was assessed biannually during six years for total culturable aerobic bacteria at 22 °C and 36 °C, Legionella sp., Pseudomonas aeruginosa, and total coliforms. A total of 628 samples were analyzed, 99.8% were compliant with extended microbiological levels, and we never detected pathogen bacteria like Legionella sp. and P. aeruginosa. Only one sample (0.2%) was noncompliant with the level of total culturable aerobic bacteria at 36 °C, which exceeded 140 colony forming units per mL. The protocol implemented in our university hospital gives excellent results and enables control of the microbiological quality of DUWL water in the long term.

Effectiveness and safety of low-concentrated ozonized water for the reduction of contamination in dental unit water lines

Contamination of dental unit waterlines (DUWL) with heterotrophic bacteria can cause problems in immune compromised patients (aged, tumor and organ transplantation-patients). We focused on the use of low-concentrated ozonized water (OZW) as the biofilm formation restraint system for DUWL. Here, we examined the effects of low-concentrated OZW on the growth of bacteria and related biofilm formation and harmfulness to dental unit components (DUCs) in vitro. ObjectivesTo evaluate the bactericidal effects of OZW on biofilms in DUWL and DUC in vitro. MethodsLow-concentrated OZW (0.4 mg/L) was generated using an OZS-PTDX generator. Heterotrophic bacterial biofilms in old DUWL tubes and Candia albicans solution (control microbe) were treated with OZW for 1 h with gentle agitation before static culturing for 96 h in Reasoner's 2A liquid media. The control solutions were 0.1% cetylpyridinium chloride (CPC), chlorinated tap water (TW), and phosphate-buffered saline (PBS). Adenosine triphosphate (ATP) amounts of the microbes were measured and the biofilms of these microbes were observed using scanning electron microscopy (SEM). Moreover, surfaces of DUC soaked in OZW and TW were observed by SEM. ResultsThe OZW reduced ATP levels in microbes to 50% compared to TW and PBS treatment, although CPC reduced it below detection limits. SEM observation revealed deformation of microbes cultured with OZW, whereas no changes were seen on DUC surfaces. ConclusionsLow-concentrated OZW is bactericidal against heterotrophic bacteria biofilms and it is not harmful to DUC, suggesting that it might be useful in preventing DUWL contamination.

Plasma Sterilization Effectively Reduces Bacterial Contamination in Dental Unit Waterlines.

Objective To investigate the effectiveness of plasma sterilization in reducing bacterial contamination and controlling biofilms in dental unit waterlines. Materials and Methods Ten identical dental chair units (DCUs) were used. Five DCUs were installed with an automated plasma sterilization system (PSS) and the other five were kept as nontreated controls (CTL). Water flushed from the airotor line served as the output water of the dental unit waterlines (DUWLs). Water samples were collected at the beginning and on a weekly basis for 4 months. Water was analyzed for bacterial contamination (CFU/mL). Scanning electron microscopy (SEM) was used to investigate the amount of biofilm in the waterlines. Biofilm viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays. All statistical analyses were performed using the Mann–Whitney U test. A value of p < 0.05 was considered significant. Results The DCU output water was found to be heavily contaminated with bacteria. Plasma sterilization effectively reduced bacterial contamination from an average of 212 CFU/mL to 8 CFU/mL. During the entire period of 4 months, the level remained below 500 CFU/mL, the standard level recommended by the Centers for Disease Control and Prevention (CDC) of the USA. The reduction in the bacterial count was significant compared with the CTL group (p < 0.05). Plasma sterilization could not eradicate the existing biofilms in the waterlines, and it did reduce biofilm mass and viability. Moreover, treatment with plasma sterilization did not induce a change in the composition of microorganisms, as analyzed by Gram staining. Conclusion Plasma sterilization, which is part of electrochemically activated water, effectively reduces bacterial contamination and reduces biofilms in dental unit waterlines.

Comparative evaluation of the chlorhexidine and cinnamon extract as ultrasonic coolant for reduction of bacterial load in dental aerosols.

Background:Ultrasonic instruments generate aerosols with significantly greater number of bacteria. Preprocedural mouthrinses or chemotherapeutic coolants are used for the reduction of bacterial load in dental aerosols. The use of chlorhexidine as an ultrasonic coolant has been well established. However, this application has not yet been investigated for cinnamon extract which is known to have antibacterial and anti-inflammatory properties in vivo.Aim:The aim of this study is to compare and evaluate the efficacy of chlorhexidine and cinnamon extract as an ultrasonic coolant in reduction of aerosol contamination and biofilm formation during ultrasonic scaling in comparison with the distilled water (DW).Materials and Methods:Sixty patients diagnosed with moderate-to-severe gingivitis were randomly divided into three groups of twenty patients each undergoing ultrasonic scaling. For Group I, chlorhexidine was used as an ultrasonic coolant; for Group II, cinnamon extract was used; and Group III was served as control where DW was used. The aerosols from ultrasonic units were collected on two blood agar plates at three different positions. Both the plates from each position were incubated aerobically for 48 h. The total number of colony-forming units were counted as mean ± standard deviation and statistically analyzed. In addition, biofilm sampling of dental unit waterlines (DUWLs) was also done to evaluate the effect of these antimicrobials. Apart from microbial examination, clinical parameters such as plaque index and gingival index were also evaluated at baseline and 1-month follow-up.Results:Chlorhexidine and cinnamon both were equally effective (P > 0.05) in reducing the bacterial count in aerosols and biofilm in DUWL as compared to DW when used as ultrasonic cooling agent.Conclusion:Both cinnamon and chlorhexidine used as an ultrasonic device coolant through DUWLs effectively helped in the reduction of bacterial count in dental aerosols.

Application of D-Amino Acids as Biofilm Dispersing Agent in Dental Unit Waterlines.

Aim and Purpose Biofilms in dental unit waterlines (DUWLs) are extremely difficult to eliminate. Aim of this study is to evaluate the efficacy of a mixture of four D-amino acids on biofilm dispersion in DUWLs. Materials and Methods A mixture of four D-amino acids (D-methionine, D-tryptophan, D-leucine, and D-tyrosine, 10 mM each), distilled water (control), and 0.1 M hydrochloric acid (HCl) was used in the experiment. In laboratory, pieces of DUWLs covered with biofilms were submerged in different solutions for 5 days, flushed, and measured OD600 of the dispersed biofilms. Remnants of biofilms on the DUWLs were evaluated by SEM. In clinic, fifteen DCUs were incubated with test and control solutions, flushed, and measured OD600 of the dispersed biofilms. Microbial count of DUWL output water was enumerated twice a week for four weeks. Results There was a slight, but not significant, increase in OD600 of flushing water in D-amino acids group. D-amino acids effectively reduced bacterial plaque as demonstrated by SEM. Incubation with D-amino acids significantly reduced biofilms especially after the first day of flushing. Bacterial count in DUWL output water was significantly reduced after treatment with D-amino acids. Conclusion D-amino acids are applicable as biofilm dispersing agents in DUWLs.

Establishing a laboratory model of dental unit waterlines bacterial biofilms using a CDC biofilm reactor

In this study, a laboratory model to reproduce dental unit waterline (DUWL) biofilms was developed using a CDC biofilm reactor (CBR). Bacteria obtained from DUWLs were filtered and cultured in Reasoner’s 2A (R2A) for 10 days, and were subsequently stored at −70°C. This stock was cultivated on R2A in batch mode. After culturing for five days, the bacteria were inoculated into the CBR. Biofilms were grown on polyurethane tubing for four days. Biofilm accumulation and thickness was 1.3 × 105 CFU cm−2 and 10–14 μm respectively, after four days. Bacteria in the biofilms included cocci and rods of short and medium lengths. In addition, 38 bacterial genera were detected in biofilms. In this study, the suitability and reproducibility of the CBR model for DUWL biofilm formation were demonstrated. The model provides a foundation for the development of bacterial control methods for DUWLs.

Dental Unit Water Lines and their Disinfection and Management: A Review.

The perceived threat to public health from dental unit water line (DUWL) contamination comes from opportunistic and respiratory pathogens such as Legionella spp, Nontuberculous Mycobacteria (NTM) and pseudomonads. These organisms can grow and multiply in the DUWL biofilm to reach infective concentrations, with the potential for inhalation leading to respiratory infections or direct contamination of surgical wounds. In this paper we discuss current legislation and practical methods for delivering water within the DUWL that meets the standards for safety. Clinical relevance: Understanding the clinical relevance and methods for decontaminating DUWL is essential to create a safe working environment in dentistry.

Microbial assessment of dental unit waterlines in an institutional setup in Karnataka, South India.

Biofilms in dental unit waterlines (DUWLs), suction hoses, and fittings are a potentially significant source of cross-contamination posing significant health risk as these may come into contact with patients during treatment. The purpose of this in vitro study was to identify the spectrum of bacterial flora colonizing the DUWLs and to detect pathogenic microorganisms present in such an environmental niche. Thirty DUWL samples were collected from in use dental units selected randomly from various clinical departments. Samples were collected from the following devices; 3-in-1 syringe waterline, section of waterline tubing supplying the 3-in-1 syringe, and the air rotor water. The samples were subjected to bacteriological analysis, and all bacterial isolates were tested for their ability to form biofilms. A descriptive analysis of the results obtained was carried out, and it was observed that 7 out of 30 (23.3%) samples collected from DUWL were supplying water of unsatisfactory quality with species of low-pathogenicity bacteria isolated present in significant numbers; four of ten (40%) water supply lines contained bacterial biofilms; and the species with greatest capability to form biofilms were Enterobacter species (spp.). In addition, the results were also subjected to Chi-square test which revealed no statistical difference between the species and the location of collection of samples. Within the limitations of this study, it is concluded that DUWLs are not totally free of contamination. Microbial biofilms are a significant source of cross-contamination and cross-infection in the dental clinic environment.

Application of Scanning Electron Microscopy in the Detection of Biofilm in Dental Unit Waterlines

Infection control plays a major role in health care, including dentistry. Microbial contaminations in dental unit waterlines (DUWLs) are very common. In the present study, the formation and characterization of biofilm in the inner lumen of the dental unit waterlines (DUWLs) was examined using scanning electron microscopy (SEM). Four dental chairs were selected in the department and new dental unit waterline tubes were installed. A new tube was taken as control. The conservative and endodontic procedure was carried out in the dental chair. The tubes were removed from the dental chairs at different intervals- 7 th day, 10 th day, 13 th day and 16 th day. The biofilms in the inner lumen of the tube is analyzed for the presence of biofilm using scanning electron microscopy. SEM showed the progressive development of biofilms in the dental unit waterlines. The density of the biofilm increased as the duration of installation of tube increased. Biofilm formation was detected in all the tubes except the control. Detection of biofilm in the dental unit waterlines within a week emphasis the need for reliable and effective disinfection protocols in the dental office to eliminates the biofilm within the dental unit waterlines.

Effect of Different Disinfection Protocols on Microbial and Biofilm Contamination of Dental Unit Waterlines in Community Dental Practices

Output water from dental unit waterlines (DUWLs) may be a potential source of infection for both dental healthcare staff and patients. This study compared the efficacy of different disinfection methods with regard to the water quality and the presence of biofilm in DUWLs. Five dental units operating in a public dental health care setting were selected. The control dental unit had no disinfection system; two were disinfected intermittently with peracetic acid/hydrogen peroxide 0.26% and two underwent continuous disinfection with hydrogen peroxide/silver ions (0.02%) and stabilized chlorine dioxide (0.22%), respectively. After three months of applying the disinfection protocols, continuous disinfection systems were more effective than intermittent systems in reducing the microbial contamination of the water, allowing compliance with the CDC guidelines and the European Council regulatory thresholds for drinking water. P. aeruginosa, Legionella spp, sulphite-reducing Clostridium spores, S. aureus and β-haemolytic streptococci were also absent from units treated with continuous disinfection. The biofilm covering the DUWLs was more extensive, thicker and more friable in the intermittent disinfection dental units than in those with continuous disinfection. Overall, the findings showed that the products used for continuous disinfection of dental unit waterlines showed statistically better results than the intermittent treatment products under the study conditions.

Effect of nanoemulsion on dental unit waterline biofilm

Bacterial biofilm in dental unit waterlines (DUWLs) is a widespread problem and poses a potentially significant risk of infection to dental staff and patients. The present study investigates the level and composition of bacterial contamination of dental chair syringe waterlines and investigates the efficacy of a cetylpyridinium chloride-containing nanoemulsion disinfectant in reducing bacterial loads. Waterline biofilms exposed to nanoemulsion for 1 hour, 6 hours, 12 hours, 24 hours, 48 hours, and 72 hours showed high reduction of colonies, and very low counts after 12 hours and 24 hours (67 colony-forming units/mL) were observed. Exposures for 48 hours and 72 hours showed no or few visible colonies (2 colony-forming units/mL). The nanoemulsion employed improves efficacy against microorganisms more than unemulsified components. DNA sequencing showed that the organisms in the waterline biofilm are primarily of soil or water origin. The findings indicate that nanoemulsion effectively disinfects waterlines to consistently meet the American Dental Association (ADA) recommendation.

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.

Isolate-Specific Effects of Patulin, Penicillic Acid and EDTA on Biofilm Formation and Growth of Dental Unit Water Line Biofilm Isolates

Dental unit water line (DUWL) contamination by opportunistic pathogens has its significance in nosocomial infection of patients, health care workers, and life-threatening infections to immunocompromized persons. Recently, the quorum sensing (QS) system of DUWL isolates has been found to affect their biofilm-forming ability, making it an attractive target for antimicrobial therapy. In this study, the effect of two quorum-sensing inhibitory compounds (patulin; PAT, penicillic acid; PA) and EDTA on planktonic growth, AI-2 signalling and in vitro biofilm formation of Pseudomonas aeruginosa, Achromobacter xylosoxidans and Achromobacter sp. was monitored. Vibrio harveyi BB170 bioassay and crystal violet staining methods were used to detect the AI-2 monitoring and biofilm formation in DUWL isolates, respectively. The V. harveyi BB170 bioassay failed to induce bioluminescence in A. xylosoxidans and Achromobacter sp., while P. aeruginosa showed AI-2 like activity suggesting the need of some pretreatments prior to bioassay. All strains were found to form biofilms within 72 h of incubation. The QSIs/EDTA combination have isolate-specific effects on biofilm formation and in some cases it stimulated biofilm formation as often as it was inhibited. However, detailed information about the anti-biofilm effect of these compounds is still lacking.