Pneumonia associated with a dental unit waterline

L pneumophila is a Gram-negative bacterium ubiquitous in natural water environments and found also in man-made water systems; it can infect people by inhalation or microaspiration of aerosolised water causing a severe pneumonia known as Legionnaires' disease, mainly affecting elderly and immune-compromised patients, or a flu-like disease, known as Pontiac fever. Sources of infection have been shown to be primarily air-conditioning systems, hot-water systems, spas, and fountains.3 Significant contamination of dental unit waterlines with legionella has been widely documented.4 Serological studies have also shown a higher prevalence of antibodies to L pneumophila in dentists and dental practice staff, suggesting a potential health risk for these workers.4 However, as far as we are aware, no case of Legionnaires' disease has been associated with this source of infection.