Legionella Overview

Legionnaires' disease (the most severe form of Legionellosis) is a form of pneumonia that is caused by inhalation or aspiration of bacteria that belong to the family Legionellaceae. This family includes 48 species and 70 serogroups. Legionellosis is most commonly linked to exposure to Legionella pneumophila, however, other species (i.e., L. micdadei, L. anisa ) can cause the disease as well. The name Legionella pneumophila was coined after the original outbreak of the disease at the American Legion convention in Philadelphia in 1976. L. pneumophila has many sub-groups called serotypes. L. pneumophila serotype 1 and 6 are commonly associated with Legionnaires disease.

ECOLOGY
Legionella are commonly found in aquatic environments and some species have been found in soil. The organisms are found in a wide range of environmental conditions and are relatively resistant to low pH, dissolved oxygen levels, and routine chlorination techniques for drinking water. Temperatures above 104° F promote rapid multiplication of the organism. The organisms are consistently found in the biofilm that forms in aquatic environments, cooling towers and potable water systems.

EPIDEMIOLOGY
The risk factors for Legionellosis in decreasing order of importance are heavy smoking, chronic lung disease, the elderly, and the immunosuppressed. A recent study has documented 76 cases of pediatric Legionellosis in children under 1 year of age or children with underlying medical conditions such as malignancy or immunosuppression. Legionellosis is not contagious; there is no evidence that the disease can be transmitted form person to person. Exposure must be thru inhalation or aspiration of contaminated, aerosolized water. Once a person has Legionnaires disease, getting it a second time is extremely rare.

MONITORING GUIDELINES
The US Centers for Disease Control (CDC) recommends routine monitoring for Legionella in all bone marrow and organ transplant hospitals nationwide. Routine monitoring in healthcare facilities is recommended or required in several states such as NY, TX, MD, Los Angeles County and Allegheny County PA. Canada has guidelines for monitoring healthcare facilities. The American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) recommends routine monitoring of building water supply systems.

SAMPLING and ANALYSIS
Take a 1000ml sample for potable water and a 250 ml sample for non-potable water. (Be sure to use sterile bottles with a chlorine neutralizing agent.) It is also recommended to take sterile swab samples of biofilm in areas where it is present. Sample should be shipped overnight to the lab on freezer packs. Culturable analysis either by the US Center for Disease Control or the International Standard Organization is the "gold standard" and requires 10-14 days. Testing by Polymerase Chain Reaction (PCR) takes 2-3 days and is very useful for providing fast, presumptive results to reduce liability during an outbreak. Isolating Legionella from environmental samples is difficult. Make sure you use only an experienced lab with qualified analysts and a sound quality control program.
For Further Information, Contact Diane Miskowski at 1-800-220-3675 Ext. 1218

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Latest Article

An Overview of Legionella Analyses

By Diane Miskowski, MPH EMSL Analytical, Inc.

The first recognized outbreak of Legionnnaires' Disease occurred in the US at the American Legion Convention in Philadelphia during the summer of 1976. read more...

Additional Resources

For additional information please click the links below.

Legionnaires' Disease
Clinical Microbiology Reviews
Cooling Technology Institute
more resources...

Legionella images courtesy of CDC, Public Health Image Library (PHIL)