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FAQ FOR INVESTIGATORS OR RESEARCHERS

I am a physician at the District Health Office. We have noticed an increase in the number of reported cases of Legionnaires' disease. These have all been non-nosocomial, non-travel associated Legionnaires' disease, with a number of patients barely
leaving their houses. It was decided to test the domestic and municipal water supplies for the presence of legionella. We also tested the water of premises where there had been no Legionnaires' disease.  Having found legionella, the correct course of action is not entirely clear. We have identified 3 possible scenarios and would be grateful if you could advise. 

1. Legionella found in the domestic water supply of a known Legionnaires' disease patient.

      Ideally, molecular subtyping of the patient isolate and the environmental isolate would support that the source of the Legionella is from the home.  However, I know the legionella isolate from the patient often is not available from the patient especially if the
diagnosis was made by the urinary antigen test.

      That said, the home could be disinfected because of the occurrence in the patient's home. Certainly, the patient and the family would feel safer. Disinfection is also suprisingly easy in a residence.  Superheat and flush can be used. The flush should be at least 30 minutes - see our website for details of the superheat and flush (Publications on disinfection by YSE Lin, 1998 ).

2.    Legionella found in the domestic water supply of healthy individuals.

      No action.  The reason is clearcut.  Legionella can be found in the majority of buildings over 3 stories tall.  Since it is a common colonizer of drinking water, all individuals are exposed on a regular basis to legionella.
 

3. Legionella found in the domestic water supply of those with lung disease of immunocompromised patients, in the absence of Legionnaires' disease.

      This is a gray area in which a number of reasonable options can be considered.  We do not recommend disinfecting the water in this situation. For persons with chronic lung disease (especially those with a history of bronchitis or pneumonia) or are immunosuppressed, we recommend that they not drink tap water - either in their home or outside of their home.  Instead, we would recommend that tap water can be boiled and then cooled and refrigerated for drinking (see Singh N. Prevention of Legionnaires’ disease in transplant recipients Transplant Infect Dis 2004 on our home page) for further details. 

Do you advocate the testing of domestic premises for legionella?
      No.  See our Reply to Question #2. The logical site to perform culturing of drinking water would be a building in which high risk individuals congregate; in such a situation, environmental culturing would be cost-effective.  That specific situation is a hospital and many countries now routinely culture their water supply.  The results allow the hospital to make a rational decision on how to prevent a preventable infection. Such a policy has been implemented in Pittsburgh, state of Maryland, Spain, France, Denmark, Taiwan, Netherlands, Italy, and Germany.

Two other points:  Legionella is not contracted via showering. The major mode of transmission of legionella is not aerosolization, but aspiration.  So cooling towers are overemphasized as sources of Legionnaires’ disease.

 

Recently we have witnessed an increase in the number of patients diagnosed with legionella in our district. Apart from the known risk factor for legionellosis (smoking, diabetes mellitus, and immunocompromised states) we noticed that 30% of them became ill after flying from or to the country from different areas. The entity of travel- associated legionella is well known but I would like to hear your opinion regarding the possible influence of traveling itself, especially by air, upon the susceptibility of the exposed people to develop disease.

      I do not believe that travel itself, either air or otherwise, plays any direct role in the acquisition of legionnaires' disease. I believe that the risk factor is the large buildings, e.g., hotels or cruise ships in which the drinking water is colonized with Legionella-to which the traveler is exposed.  The solution is not easy since only a small fraction of individuals who stay at these hotels contract Legionnaires' disease, and that they may also be exposed to drinking water colonized with Legionella from buildings other than hotels.  If a significant increase in travel-associated Legionnaires’ disease is being seen in your district, a study should be performed by your Health Department noting the characteristics of the patients (cigarette smoking is more important than diabetes) and the sources of drinking water to which they were exposed.

 

L. pneumophila serogroup 13 and drowning:   A female aged 27 year old was admitted to intensive care unit with respiratory failure due aspiration pneumonia after drowning in river Clyde in Glasgow Scotland-UK.  Culture of tracheal aspirate yielded growth of Legionella pneumophila serogroup 13.  The patient seroconverted to Legionella pneumophila serogroup 13 before she died of respiratory failure.

My questions are:

1. How significant is Legionella pneumophila serogroup 13 in a patient with aspiration pneumonia?

       Serogroup 13 is extremely unusual and we have never documented a culture-confirmed case.  However, Mona Schousboe New Zealand and Chris Heath Australia have documented 1 case each of culture-confirmed serogroup 13 in community-acquired legionellosis.  (Yu VL, et al J Infect Dis 2002; 186:127-128). In this international surveillance study of culture-confirmed community-acquired LD, 2/508 patients were infected by serogroup 13.

 

2. Has this particular serogroup been associated with Legionnaires disease in patient who drowned in urban river water?

        No. There have been 2 cases of drowning associated with Legionnaires’ disease. A serogroup 10 in the Lancet 1988:2:460 and serogroup 3 Kansenshogaku Zasshi Dec 1995;69:1356-1364. This is further evidence of the importance of aspiration.

 

3. Has been any documented case fatality reports of Legionella pneumophila serogroup 13 in the literature? If Yes, Please provide the references.

        Not to our knowledge.  You have a reportable case!  I will put you in touch with Christopher Health and Mona Schousboe and you should combine your experience into an important case report. I suggest you consider Emerging Infectious Disease as the journal for submission. 

Epilogue:  Faris B, Faris C, Schousboe M, Heath CM.  Legionellosis from L. pneumophila serogroup 13.  Emerg Infect Dis 2005; 11:1407-1411.

 

Why is endotoxin not a virulence factor for Legionella since it is a gram-negative bacterium?  I work in a biotech company and develop assays for endotoxin detection.  I am thinking of using endotoxin detection as a method for environmental monitoring (not for diagnosis). 

        No clinical evidence has suggested the possibility of endotoxin-mediated disease in humans. Endotoxin is not used for diagnosis and is not a virulence factor for Legionella   A murine model showed that mortality was not related to endotoxin production (Pastoris MC, J Med Microbiol Aug 1997;46:647-655).