Legionnaires’ disease and dental unit water

March 1, 2012
On a certain Monday morning in February, some of us were getting the same question from our patients.

On a certain Monday morning in February, some of us were getting the same question from our patients. The question was similar to the questions that dental offices received in 1987 regarding transmission of HIV in the dental setting, as well as questions in 2001 regarding the transmission of HBV in the dental setting. My hope was that you answered these questions without hesitation.

Your current answers should be that your office is doing everything they can to comply with the guidelines, regulations, and laws governing infection control in the dental setting, including infection control procedures that treat the water lines.

In Rome, Italy, it was confirmed that an 83-year-old Italian woman who died from Legionnaire’s disease contracted the infection from the water lines in a dental practice.

The case was quickly diagnosed, and the source of the disease is unquestioned. The woman was admitted into the hospital with breathing problems and a very high temperature. She was admitted to the intensive care unit with continued fever and respiratory distress.

Chest radiography showed several areas of lung consolidation. She had no underlying diseases or conditions. Legionnaires’ disease was promptly diagnosed by a Legionella pneumophila urinary antigen test; a bronchial aspirate was taken for microbiological examination. Oral ciprofloxacin (750 mg every 12 hours) was started immediately. Nevertheless, the patient developed fulminant and irreversible septic shock and died two days later. An investigation to find the source of L pneumophila infection was initiated. After testing, she was diagnosed with legionnare’s disease.1,2

The part of this story that makes it clear that the disease was a direct result of dental treatment is what led up to this. The patient left her house only two times within the incubation period of two to 12 days. Both of those trips were direct trips to the dentist and back.

The evaluation of the dental setting included an evaluation of the water in the dental lines. Samples of water were taken from the dentist’s tap, from the dental unit water line, and from the high-pressure pump supplying the waterline. The testing that was done revealed that all three samples of water tested positive for Legionella pneumophila bacteria and the sample from the water pump was particularly convincing. Aerosolised water from high-speed turbine instruments was most likely the source of the infection. Warm temperatures and periods of water immobility provide a breeding ground for the bacteria. Distributed in fine droplets by a spray, the bacteria are then breathed in. Elderly people or individuals with poor immune systems are most at risk.

Genetic sequencing confirmed that the bacteria found in the dental water line directly matched the bacteria that killed the patient. The bacteria is a particularly virulent substrain called Benidorm.

Legionnaire’s disease, as we all know, is unusual. Most cases have involved air conditioning units, spas, and water fountains that are not properly cleaned or looked after. No one previously has identified the dental setting as a possible source of this disease, but we all know it could happen. That is why we are all so diligent in applying infection control guidelines, regulations, and laws into our daily practice of dentistry.

The case report has suggested a number of recommendations, including the use of filters and sterile water and adding a continuous loop of disinfected water.

What is Legionnaires’ disease?

The Centers for Disease Control and Prevention (CDC) defines Legionnaires’ disease as a disease that is caused by a type of bacteria called Legionella. The bacteria got its name in 1976, when many people who went to a Philadelphia convention of the American Legion suffered from an outbreak of this disease, which is a type of pneumonia (lung infection). Although this type of bacteria was around before 1976, more illnesses from Legionnaires’ disease are being detected now. This is because we are now looking for this disease whenever a patient has pneumonia.

Legionella bacteria are found naturally in the environment, usually in water. The bacteria grow best in warm water. This is why you will find it in places such as hot tubs, air conditioning units, and water tanks. People aquire Legionnaires’ disease when they breathe in a mist or vapor (small droplets of water in the air) that has been contaminated with the bacteria. One example might be from breathing in the steam from a whirlpool spa that has not been properly cleaned and disinfected, or a dental hand-piece that has water flowing through to cool it down that is aerosolized. This disease is not spread from one person to another, but rather from the environment to the person.

The populations at the greatest risk for developing this disease are older people (usually 50 years of age or older), people who are current, former smokers, those who have a chronic lung disease (such emphysema), people who have weak immune systems from diseases, or those who take drugs to suppress (weaken) the immune system.

The problem with diagnosis of this disease is that symptoms are similar to other forms of pneumonia. It may be hard to diagnose at first. Symptoms of the disease can include a high fever, chills, and a cough. Some people may also suffer from muscle aches and headaches. Chest X-rays are needed to find the pneumonia caused by the bacteria, and other tests can be done on sputum (phlegm), as well as blood or urine to find evidence of the bacteria in the body. Symptoms usually begin two to 14 days after being exposed to the bacteria.

Legionnaires’ disease can be very serious and can cause death in 5% to 30% of cases. Most cases can be treated successfully with antibiotics, and healthy people usually recover from infection.

Dental unit water lines

We all know that large numbers of potentially pathogenic microorganisms can be harbored in the dental unit water lines. Controlling the bacteria level and biofilm in the small diameter water lines that feed into equipment that can be a source of contamination is vital to patient and operator health. Several studies have confirmed the risks involved in small tubing of these systems and their propensity to foster the growth of pathogens.3,4,5 According to these studies, bacterial species found in aquatic environments, although present in low numbers in drinking water, can be found in very high numbers in the water lines of dental units.

In late 2003, the CDC issued updated guidelines for dental infection control, including general recommendations for dental unit waterlines, biofilm, and water quality. The Food and Drug Administration (FDA) has cleared numerous devices for use with the dental units, including bottled water systems, filters, and water purification units. The Environmental Protection Agency (EPA), which recently took over the regulatory jurisdiction for some chemical agents used to improve dental water quality, is in the process of creating guidance for manufacturers who wish to register their products with antimicrobial claims. Awareness of this issue among practicing dentists has risen dramatically, and increasing numbers of dentists are taking measures to improve water quality.6

Where can I get the information I need?

Organization for Safety, Asepsis and Prevention (OSAP) is one of the greatest assets that dental professionals have. Every dental office should join this organization to stay updated and aware of all issues in infection control in the dental setting. Go to OSAP.org to make the most of the countless resources available. They have great resources for understanding the importance of water safety in the dental setting.

As dental professionals we are exposed everyday to the environment that this lady experienced.Because of daily exposure, dental professionals may be at greater risk than patients. While looking for evidence of exposure to legionella in the dental environment it has been discovered that dental professionals have higher titres of legionella antibodies than the general population.7,8 There is also a case in California where a dentist is suspected of dying from legionella dumoffi species acquired from his dental unit water lines. Investigators were able to determine that his office water supply contained 100,000 cfu/ml, while the count in his home water supply was below 100 cfu/ml9.

It is vital that we do everything to ensure that the water we are using in the dental setting is safe for both the patient and the clinician. Our daily practices with personal protective equipment must include masks that are worn properly, changed when damp, and between patients as the CDC recommends.

Utilizing the checklist from OSAP will help dental offices confirm that they are doing everything they can to keep the patients and staff safe. The letter that OSAP has developed will reassure patients and help them to understand that our first and greatest concern is our patients. RDH


1. http://www.dentistryiq.com/index/display/news-display/1606083009.html
2. http://abcnews.go.com/Health/woman-contracts-legionnaires-disease-dental-water/story?id=15699616
3. Cabot AL, Miller RL, Micik RE, Ryge G. Studies on dental aerobiology: IV. Bacterial contamination of water delivered by dental units. J Dent Res 1971; 50(6):1567-1569.
4. Beierle JW. Dental Operatory Water Lines. Calif Dent Assoc J 1993; 21(2):13-5.
5. Whitehouse RLS, Peters E, Lizotte J, Lilge C. Influence of biofilms on microbial contamination in dental unit water. J Dent 1991; 19:290.
6. http://www.osap.org/?page=Issues_DUWL
7. Shojaei M, Staat RH. Disinfectioin of dental unit water lines using hydroperoxide; preliminary data. Journal of Dental Research 1997; Abstract 332
8. Reinthaler FF, Mascher F, Stinzner D. Serological Examinations for Antibodies against Legionella Species in Dental Personnel. J Dent Res 1988; 67(6):942-3.
9. Atlas RM, Williams JF, Huntingdon MK. Legionella contamination of dental unit waters. Appl Environ Microbiol 1995;61:1208-1213

Noel Brandon Kelsch, RDHAP, is a syndicated columnist, writer, speaker, and cartoonist. She serves on the editorial review committee for the Organization for Safety, Asepsis and Prevention newsletter and has received many national awards. Kelsch owns her dental hygiene practice that focuses on access to care for all and helps facilitate the Simi Valley Free Dental Clinic. She has devoted much of her 35 years in dentistry to educating people about the devastating effects of methamphetamines and drug use. She is a past president of the California Dental Hygienists’ Association.

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