International Journal of Public Health Dentistry

Transcription

1 RESEARCH ARTICLE Evaluation of bacterial contamination of dental unit waterlines and the efficacy of commercially available disinfectants Mitesh Devichand Kathariya, Patil Swapnil Kashinath, Sadanand Kulkarni, Deepesh Singh, Basavaprabhu Akkareddy, Renuka Kathariya. Abstract Background: Microbial colonies that adhere to solid surfaces wherever there is sufficient moisture are referred to as the biofilms. The microbes acquire a slimy covering called glycocalyx, which protects them, in a moist environment. Biofilms formed in dental unit water lines can act as a source of cross infection. Aim: To evaluate the bacterial contamination of dental unit water lines and the efficacy of commercial disinfectants in eliminating biofilms from dental unit water lines. Methods: To begin with, random water samples were collected from water booster, air-turbine, air water syringe of two dental units and were subjected to bacteriological analysis. Commercially available disinfectants 0.2% chlorhexidine and 3% sodium hypochlorite, were used to treat the two dental unit water lines respectively. Water samples from different parts of dental unit water lines were collected on the third, fifth seventh,twelfth, fifteenth,and seventeenth day following treatment with the disinfectants and the samples were sent for microbial analysis.results: Bacterial isolates were observed before treatment with 0.2% chlorhexidene and 3% sodium hypochlorite but there were no bacterial isolates after treatment with disinfectants for a period of 15 days. Conclusions: Usage of disinfectants was found to be very effective for a period of 15 days. For maintenance of sterility of dental unit water lines easily available and cost effective disinfectants can be used in day to day dental practice supplemented with a a good source of water, and the use of an anti-retraction valve. Keywords: Dental unit waterlines; Disinfection; Biofilm; Chlorhexidine; Sodium hypochlorite. Introduction protozoa on the inner surface of the water lines, forming a biofilm (2). Due to a Effective infection control is one of the combination of negative publicity and an cornerstones of good practice and clinical increased scientific knowledge of dental unit governance. Microbial colonies that adhere to waterlines (DUWL) biofilms and their solid surfaces wherever there is sufficient associated risks, contamination of dental unit moisture are referred to as the biofilms. The waterlines has become a prominent infectioncontrol existence of contaminated water in dental issue (3). More than 25 different units appears to have first been reported in genera of bacteria have been detected in 1963 in Great Britain by Dr.G.C. Blake. He dental-unit water, along with occasional fungi was also the first to test the effectiveness of and protozoa (4). The predominant bacteria chemical germicides as a possible solution to isolated from biofilms arc Gram -ve organisms the problem (1). The source of bacterial like Pseudomonas, E. Coli, Legionella, Nontuberculous contamination within the dental unit water mycobacterium, others like supply is thought to be caused by microcolonies Staphylococcus, Bacillus, Actinobacter, of proliferating bacteria, fungi and Klebsiella pneumoniae, and Flavobacterium :4(1): Publishing Division, Celesta software Private Limited

2 With the emergence of opportunistic infections in the last few decades, many of these organisms typically recovered from dental unit water systems could prove harmful. The perceived threat to public health from DUWL contamination comes from opportunistic and respiratory pathogens such as Legionella spp (causative agent of the pneumonia, Legionnaires disease), Mycobacteria spp and Pseudomonas. These organisms can be amplified in the biofilm to reach infective concentrations, with the potential for inhalation or direct contamination of surgical wounds (1). Research has shown that microbial counts can reach as high as 200,000 CFU/ml within five days after installation of new dental unit waterlines and levels of microbial contamination as high as 10 6 CFU/ml have been documented. Of recent standard microbial culture techniques, as well as new analytical techniques, have revealed extraordinary numbers of a wide variety of waterborne "opportunistic" pathogens. These bacteria are quick to take advantage when the immune system defenses are low, with immunocompromised patients especially at risk. The bacteria found in dental water lines may cause significant infection in these individuals.cystic fibrosis, which occurs in one in 3500 Caucasian births, results in chronic pulmonary disease. Death is most often the result of respiratory failure, typically after many episodes of lung infection. The most common cause of these infections is pseudomonas, which are the dominant bacteria found in dental spray water. Legionella, the bacteria which cause Legionnaires' disease, are Disease Control has implicated Legionella bacteria as a major complication for people with AIDS. During the last five years the American Dental Association (ADA) has specifically targeted DUW, promoting research and technical developments. The ADA recommended that dental unit water should comply with drinking water standards and contain <200 colonies/ml of bacteria (5) (equivalent to that permitted for drinking water).this standard has been adopted by other national dental organization as being acceptable and achievable. To control contamination of DUWL, the British Dental Association recommends flushing, independent bottled water systems, antiretraction valves on hand pieces, and use of sterile water for minor oral surgery. There are a plethora of automated flushing systems, filters, water disinfectants, independent bottle water systems, and even fully detachable autoclavable DUWL in the market. Many workers have suggested treatment with various disinfectant solutions, including hydrogen peroxide(6), chlorhexidine gluconate(7), sodium hypochlorite(8,9), chlorine dioxide(10), povidone iodine (11), Listerine mouthwash (12), and electrochemically activated water (13). These have been developed and implemented in many dental practices with mixed long-term results. The present study was undertaken to study the efficacy of commonly available disinfectants like 0.2% chlorhexidine and 3% sodium hypochlorite in dental practice as these agents are easily available, cost effective and present in most dental set ups. Materials and Methods present in dangerously high concentrations in The study was undertaken in the department the majority of dental chairs. The Center For :4(1): Publishing Division, Celesta software Private Limited

3 of Pedodontics and Preventive Dentistry, Rural Dental College, Loni, Ahmednagar district, Maharashtra, India. Two dental units, approximately 5 years old, one from undergraduate (UG) and one from post graduate (PG) clinic, were used for the study. Random water samples (20ml) were collected in sterile containers from water booster, airturbines and air-water syringe of dental units and subjected to microbiological analysis. The samples were centrifuged at 3000rpm for 5 minutes, supernatant was discarded and centrifuged deposit was used for cultures. The collected samples were subjected to both aerobic and anaerobic cultures. Viability count study was made using pour plate and most probable number technique (MPN). Commercially available disinfectants 3% sodium hypochlorite and 0.2% chlorhexidine were used on two dental units respectively and its efficacy in bringing down the bacterial count was evaluated. Method of application of commercially available disinfectant: The disinfectant solution was added in 1:1 dilution to the booster of the unit. The disinfectant solution was made to run through the system until the solution appeared at the end of the air/ water syringe and handpiece lines. The air turbine (aerotor hand piece) was always removed. Booster used was a standard glass bottle supplied by the chair manufacturer. Plastic bottle could not be used because hydrogen peroxide liberated during the action of commercially available disinfectant could burst the plastic. Once the disinfectant was flushed till it came out of the other ends, the disinfectant solution was allowed to sit in the unit overnight. The ends of waterlines were placed into a sink in case any solution dripped overnight. At the beginning of the next workday, remaining disinfectant solution was discarded and the external water bottle was rinsed with hot water.the bottle was filled with hot water, each of the dental unit water lines (air/ water syringe, handpiece lines) were flushed till froth disappeared and clear water could be seen. Water from aquaguard classic (Eureka Forbes Ltd,Mumbai, India) was made to run through the tubing. Samples were collected on the third, fifth, seventh, 12 th,15 th and 17 th day following treatment with the reagent. At a time six water samples (20ml each) were collected, one from the water booster, outlet of air/water syringe and air turbine handpiece of the two dental chairs (UG and PG) respectively on the selected days after treatment with commercially available disinfectants. All the samples were sent for bacteriological examination. Results The results of the study showed that before application of the disinfectant, Pseudomonas formed the bulk of the bacteria with a count of more than 10 5 colonies/100 ml of water, followed by aerobic spore forming bacilli 10 3 colonies and a very few colonies of Micrococci. Surprisingly Legionella species were not found in any of the samples (Table 1). Table 1: Net bacterial count before disinfection Bacteria Before disinfection Pseudomonas >10 5 colonies/100 ml Aerobic spore forming bacilli 10 3 colonies Micrococci. Few colonies Legionella species NIL After the application of the disinfectants, third, fifth, seventh, and twelfth day samples showed zero bacterial growth. The 15 th day sample :4(1): Publishing Division, Celesta software Private Limited

4 showed some bacterial growth and the 17 th day sample showed innumerable growth of bacteria especially pseudomonas species (Table 2). Table 2: Bacterial growth after disinfection with clorhexidine and sodium hypochlorite DAY After disinfection Chlorhexidine Sodiumhypochlorite Third - - Fifth - - Seventh - - twelfth - - fifteenth + + seventeenth indicates no bacterial growth, + indicates some bacterial growth (<10 3 ), ++ indicates innumerable bacterial growth (>10 5 ) Discussion The biofilm on the inner surface of the tubing of dental units provides a continuous reservoir for microorganisms (14, 15). Not only patients but also dentists and dental personnel are at risk of being infected with opportunistic pathogens such as Pseudomonas or Legionella species by means of cross-infection or following aerosol formation from water emanating from DUWS (16, 17). The contaminates adhere to luminal walls of the small bore tubing in the dental units, and over a period of weeks or months, become a dense accumulation of bioflm resulting in dense growth of microorganisms (18). Microorganisms suspended in an aqueous medium become attached to an available surface and multiply, forming micro colonies. Biofilm contamination of the dental unit water systems is a universal problem. Pseudomonas, Klebsiella, Nocardia, Streptococcus, Micrococcus, Flavobacterium, Stapyloccus, Legionella, are some of the organisms identified in dental unit waterlines. The relationship between biofilm organisms is often symbiotic with one species providing key cofactors required by another. As water moves through the tubes of a working dental unit, the water flow is faster at the centre of the lumen and more slowly away from the centre as a result of friction with the walls. It is this part of the tubing where water is virtually stagnant, allows bacteria to colonize the internal surface. As the diameter of the waterline decreases, an increasingly larger surface area relative to volume becomes available for colonization allowing the bacteria to be in contact with the water line surface for a longer period of time. Biofilms can be prevented by periodical flushing of the waterlines, use of sterile water, temperature controlled water supply and by the use of disinfectants. The various disinfectants used are sodium hypochlorite, chlorhexidine gluconate, hydrogen peroxide based solution and citric acid based products. The present study aimed at evaluating the efficacy of commonly available disinfectants; 0.2% chlorhexidine and 3% sodium hypochlorite on the microbiological water quality in dental unit waterlines. In the first part of the study, prior to the use of disinfectants for flushing dental unit waterlines, water samples were collected at random intervals. These samples were sent to the laboratory for microbiological analysis. Almost all the samples showed different isolates of microorganisms such as Pseudomonas, aerobic spore forming bacilli, and Micrococci. After allowing the disinfectant to remain in dental unit waterlines overnight, random specimens were collected on third, fifth seventh, twelfth, fifteenth and seventeenth day and subjected to microbial examination. It was found that no bacterial isolate was :4(1): Publishing Division, Celesta software Private Limited

5 encountered till the 12 th day. The 15 th day sample showed slight growth and on the 17 th day there was confluent growth especially of pseudomonas species. It was observed that the sterility was maintained for a period of 14 days. The flushing of dental unit waterlines over night would enhance the efficacy of the disinfectant to 100%. During the study it was found that Legionella species which generally predominate the bacterial contamination of dental unit waterlines was absent. Hence, it can be deduced that legionella, one of the primary contaminants of waterlines and species with pathogenic potential, as found by other studies (19, 20, 21), was not a factor under the conditions in which the present study was conducted. The study also proved beyond doubt the efficacy of disinfectants 0.2% chlorhexidine and 3% sodium hypochlorite in inhibition of bacterial growth in accordance with the previous studies (7,8).The two disinfectants were almost equally effective with no significant difference among them. In contrast to the previous studies where bacterial growth was seen after a period of seven days after use of disinfectants, no bacterial growth was demonstrated in the present study for 14 days with use of 0.2% chlorhexidine and 3% sodium hypochlorite. An analysis of the results of this study showed that the use of purified water is mandatory to begin with. To continue maintaining the sterility of the dental unit waterlines and to complete the infection control measures adopted in the dental clinics, anti-retraction valves could be incorporated into the handpiece and suitable disinfectants like 0.2% chlorhexidine and 3% sodium hypochlorite which are readily available and economical, is a must. Since the quality of water varies at different places with varying bacterial species, samples from more number of dental units with different biofilms would have probably thrown more light on the outcome of results. Based on the study results the use of chlorhexidine and sodium hypochlorite for flushing of dental units once every 15 days in routine dental practice can be recommended. Affiliations of the authors: 1. Dr. Mitesh Devichand Kathariya, Senior Lecturer, Department of Pedodontics, Rural Dental College, Pravara Institute of Dental Sciences, Loni, Maharashtra, India 2. Dr. Patil Swapnil Kashinath, Senior Lecturer, Department of Pedodontics, SMBT Dental College and Hospital, Sangamner, Maharashtra, India 3. Dr.Sadanand Kulkarni, Professor and Head, Department of Pedodontics, Aurbindo Institute of Dental Sciences, Indore, Madhya Pradesh, India 4. Dr.Deepesh Singh, Senior Lecturer, Department of Pedodontics, Pacific Dental College and Hospital, Udaipur, Rajasthan, India 5. Dr. Basavaprabhu Akkareddy, Reader, Department of Pedodontics, Singhad Dental College and Hospital, Pune, Maharashtra, India 6. Dr. Renuka Kathariya, Postgraduate Student, Department of Conservative and Endodontics, Rural Dental College, Pravara Institute of Dental Sciences, Loni, Maharashtra, India. Conflict of Interest: The author(s) declared no conflict of interests. Source of Funding: Nil. References 1. Blake GC. The incidence and control of infection in dental spray reservoirs. Br Dent J 1963; 115: Whitehouse RLS, Peters G, Lizotte J, Lilge C. Influence of biofilms on microbial contamination in dental unit water. J Dent 1991; 19: Pankhurst CL, Johnson NW, Woods RG. Microbial contamination of dental unit waterlines: the scientific argument. Int Dent J 1998; 48: :4(1): Publishing Division, Celesta software Private Limited

6 4. Tall BD, Williams HN, George KS, Gray RTS, Walch M. Bacterial succession within a biofilm in water supply lines of dental airwater syringes. Can J Microbiol 1995; 41: ADA Council on Scientific Affairs. Dental unit waterlines: approaching the year J Am Dent Assoc 1999; 130: Kellet M, Holbrook WP. Bacterial contamination of dental handpieces. J Dent 1980; 8: Douglas CWI, Rothwell PS. Evaluation of a dental unit with a built in decontamination system. Quintessence Int 1991; 22: Kim PJ, Cederberg RA, Puttaiah R. A pilot study of two methods for control of dental unit biofilms. Quintessence Int 2000; 31: Abel IC, Miler RL, Micik RE, Ryge G. Studies on dental aerobiology. IV. Bacterial contamination of water delivered by dental units. J Dent Res 1971; 50: Smith AJ, Bagg J, Hood J. Use of chlorine dioxide to disinfect dental unit water lines. J Hosp Inf 2001; 49: Mills SE, Lauderdale PW, Mayhew RB. Reduction of microbial contamination in dental units with povidone-iodine 10%. J Am Dent Assoc 1986; 113: Meiller T, Baqui A, DePaola L, Overholser CD. Disinfection of dental unit waterlines using Listerine antiseptic. J Dent Res 1995; 74: Marais JT, Brozel VS. Electro-chemically activated water in dental unit water lines. Br Dent J 1999; 187: Barbeau J. Waterborne biofilms and dentistry: the changing face of infection control. J Can. Dent Assoc 2000; 66: Putnins E, Giovanni D, Bhullar AS. Dental unit waterline contamination and its possible implications during periodontal surgery. J Periodontol 2001; 72: Bennett AM, Fulford MR, Walker JT, Bradshaw DJ, Martin MV, Marsh PD. Microbial aerosols in general dental practice. Br Dent J 2000; 189: Pankhurst CL. Risk assessment of dental unit waterline contamination. Prim Dent Care 2003; 10: Shorman HA, Nabaa LA, Coulter WA, Pankhurst CL, Lynch E. Management of dental unit water lines. Dental Update 2002; 29: Challacombe SJ, Fernandes LL. Detecting Legionella pneumophila in water systems: a comparison of various dental units. J Am Dent Assoc l995; 126: Williams H, Paszko-Kolva C, Palmer C, Kelley J. Molecular techniques reveal high prevalence of legionella in dental units. J Am Dent Assoc 1996; 127: Meiller T, DePaola L, Kelley J. Dental unit water lines: Biofilms, Disinfection and Recurrence. J Am Dent Assoc 1999; 130: Mills SE. The dental unit water line controversy: defusing the myths, defining the solutions. J Am Dent Assoc 2000; 131: Corresponding author Dr. Mitesh Devichand Kathariya, Senior Lecturer, Department of Pedodontics, Rural Dental College, Pravara Institute of Dental Sciences, Loni, Maharashtra, India. mitesh.kathariya05@gmail.com :4(1): Publishing Division, Celesta software Private Limited