GTS Legionella Water Testing Lab

Question: How does your test result compare to culture results?

Answer: Our test method produces quantitative results with environmental samples that are 10-fold to 100-fold more sensitive than culture. We use a modification of the original CDC test method; direct fluorescent monoclonal antibody (DFA) epifluorescence microscopy. Our test result of no legionella observed (<10/ml) is equivalent to a culture result of <0.1/ml to <1.0/ml, assuming that the culture procedure is properly performed and validated by the DFA monoclonal antibody test.

Question: Is your laboratory certified?

Answer: There are no federal or state certification programs for laboratories that perform legionella testing of environmental samples. Therefore, our laboratory and all others do not have a certification to perform environmental legionella testing. Therefore, care must be taken when selecting a testing laboratory.

Question: Do you use culture methods?

Answer: No, we use a modification of the original CDC test method; direct fluorescent antibody (DFA) epifluorescence microscopy. Culture methods are good during outbreaks for bio-typing; but culture methods lack sensitivity for routine, quantitative monitoring. Many factors will inhibit growth and identification of legionella on BCYE agar culture medium with or without supplements, antimicrobial agents or sample heat or acid treatment.

Question: Why do you use the direct fluorescent antibody (DFA) method?

Answer: Because we can identify non-culturable legionella that can cause outbreaks. Non-culturable, viable legionella have been reported in several peer-reviewed journals, for example, Acta Pathologica, Microbiologica et Immunologica Scandinavica 113:45-53, 2005. Only DFA tests performed by trained laboratory personnel can identify these legionella. Direct fluorescent antibody (DFA) tests using a battery of monoclonal antibodies have proven to be more sensitive and reliable with environmental water samples.

Question: Where do legionella bacteria come from?

Answer: Legionella are naturally found at the air-water interface in surface water, in ground water (Appl Environ Microbiol 71:663, Feb 2005), and in aerated biofilms. Very low numbers of Legionella enter buildings and mechanical equipment in the water supply. Legionella then may multiply to high numbers in cooling towers, evaporate condensers, air washers, humidifiers, hot water heaters, spas, fountains, car wash facilities, and plumbing fixtures. Within one month, we have observed legionella numbers in warm water-containing systems going from less than 10 per milliliter to over 10,000 per milliliter of water sample. The Europeans have reported that assumed Legionella counts in spa bulk water related to an outbreak was 1,000 to 3,600 CFU/ml (Eurosurveillance Weekley 8(21): May 20, 2004).

Question: What is Legionnaires' Disease?

Answer: Legionnaires' Disease is a serious pneumonia caused by bacteria from the genus Legionella that requires prompt medical attention. There are 8,000 to 18,000 cases of Legionnaires' Disease every year in the United States.