Legionella are a group of Gram negative bacteria that causes Legionnaires’ disease, a type of pneumonia. Legionella bacteria are found naturally in aquatic environments, preferring warm conditions. They are frequently isolated from cooling towers, hot water tanks, hot tubs and plumbing systems. There are currently a wide range of analytical methods available for screening of water samples for Legionella, including PCR, culture and fluorescent antibody techniques. However, the “gold standard” method of testing is still culture using selective media.
Culture of Legionella in water can be difficult for laboratories, particularly with samples that have high levels of background bacteria. Analyst experience is also a factor in learning to identify characteristic Legionella colonies. The U.S. Centers for Disease Control and Prevention (CDC) operates a voluntary proficiency program called “ELITE” that allows laboratories to demonstrate their ability to isolate and enumerate Legionella.
Under the ELITE Program, laboratories receive two sets of unknown samples each year. It is up to the laboratory to determine the culture method for sample analysis, but only culture techniques may be used. Results are reported to the CDC for evaluation and scoring.
Once a laboratory has demonstrated proficiency with Legionella testing, it is included in the CDC’s ELITE Members List (https://wwwn.cdc.gov/elite/Public/MemberList.aspx). Laboratories in the ELITE list have demonstrated their ability to culture Legionella and correctly identify/enumerate the colonies.
The CDC’s program is unique and important. Legionella is not a regulated pathogen in water, and state certification programs generally do not license laboratories for this parameter. This Program provides an assurance of quality in the laboratories’ test procedures.
LEGEND’s Phoenix, Arizona laboratory is proud to be a member of the CDC’s ELITE Program. LEGEND accepts both water and surface samples for Legionella culture. For more information on Legionella testing, please contact LEGEND’s Phoenix laboratory.