This week’s issue of The Lancet describes a case report of an 82-year-old woman in Italy who died of Legionnaires disease after becoming infected with L pneumophila at her dentist. This case has prompted the authors – led by Dr Maria Luisa Ricci at the Istituto Superiore di Sanita, Rome, Italy, to call for various control measures at dental surgeries to prevent similar incidents.
Suffering with fever and respiratory distress, the woman who was conscious and responsive and had no underlying disease, was admitted in February, 2011, to the intensive care unit of the “G.B. Morgagni-Pierantoni” Hospital, Department of emergency Anaesthesia and Intensive Care Unit, Forlì, Italy.
Results from a chest radiography showed multiple areas of lung consolidation. A Legionella pneumophila urinary antigen test quickly diagnosed the woman with Legionnaires’ disease and she was immediately given oral antibiotics (ciprofloxacin) every 12 hours. However, she sadly died two days later after developing rapid and irreversible septic shock, prompting an investigation to find the source of L pneumophila.
The patient had been at home for the majority of the time during the 2 to 10 day incubation period, leaving only twice to attend dentist appointments.
The investigators took water samples from the dental practice’s tap, the tap and the high-speed turbine of the dental unit waterlines, as well as from the woman’s home (shower and taps) in order to investigate possible L pneumophila contamination. They found that samples from her home tested negative for L pneumophila, but samples from the dental practice tested positive. After laboratory experiments were conducted, results showed genomic matching between L pneumphila in the dental unit waterline and in the women’s respiratory secretion.
L pneumophila is a Gram-negative bacterium found in man-made water systems and is ubiquitous in natural water environments. The bacteria can infect individuals by inhalation or microaspiration of aerosolized water causing Pontiac fever (a flu-like disease) or Legionnaires’ disease (severe pneumonia), mostly affecting immune-compromised patients and the elderly.
Spas, fountains, air-conditioning systems, and hot-water systems, have been demonstrated to be leading sources of infection.
It has been widely documented that dental waterlines are substantially contaminated with Legionella and studies have also demonstrated that the blood of dentists and dental practice staff has a higher prevalence of antibodies to L pneumophila, which indicates that people working in a dental practice environment are potentially at risk. However, prior to this case, the researchers knew no other cases in which Legionnaires’ disease had been linked to this source of infection.
The authors explain:
“The case here shows that the disease can be acquired from a dental unit waterline during routine dental treatment. Aerosolized water from high-speed turbine instruments was most likely the source of the infection. Legionella contamination in dental unit waterlines must be minimized to prevent exposure of patients and staff to the bacterium.
We suggest several control measures: use of anti-stagnation and continuous-circulation water systems; use of sterile water instead of the main water supply in the dental unit waterline; application of discontinuous or continuous disinfecting treatment; daily flushing of all outlets and before each dental treatment; use of filters upstream of the instruments; and annual monitoring of the waterline. Further useful procedures to prevent legionellosis within dental surgeries can be obtained from [already available] dedicated guidelines.”
Written by Grace Rattue