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.
Legionnaires' Disease typically causes a serious pneumonia that requires prompt medical attention.
Legionella species of bacteria cause Legionnaires' Disease. They are gram negative (but stain poorly), strictly aerobic rods.
Very low numbers of Legionella enter buildings and mechanical equipment in the water supply. Legionella then may multiply to high numbers in cooling towers, evaporative condensers, air washers, humidifiers, misters, hot water heaters, spas, fountains, car wash facilities, and plumbing fixtures.
Legionella infect people when people
inhale aerosols (small particles that do not settle out of the air)
containing these bacteria.
Legionella dispersion can extend over a
distance of at least 6 kilometers (Journal of Infectious Diseases
193:102-11, 2006)
Routine biocide treatments will not eradicate Legionella bacteria in the environment, only in laboratory studies.
Prudent practice involves removal of Legionella bacteria that cause this disease from aerosol generating equipment when the bacteria multiply to high numbers.
Once high numbers of Legionella have
been found, a relatively simple procedure for disinfecting water systems
with chlorine and detergent is available. This procedure is not part of
a routine maintenance program because equipment may become corroded.
The superheat and flush method is not an effective method to eradicate Legionella from water distribution systems (Acta Pathologica, Microbiologica et Immunologica Scandinavica113:45-53, 2005)
Legionella spp. can become heat
resistant after heating treatments for a long time. (Applied and
Environmental Microbiology, Feb. 2011, p. 1268-1275, Vol. 77, No. 4.)
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 highest number of Legionella that we have found in a water sample is 150,000 per milliliter of water.
Only 7% of the tower samples tested by our laboratory have Legionella counts greater than 200 per milliliter.
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There are no required federal or state certification programs for laboratories that perform Legionella
testing of environmental samples. Our laboratory and all
others do not have a required certification to perform environmental Legionella testing. Therefore, care must be taken when selecting a testing laboratory. |
We use a modification of the original CDC DFA test
method. We use a battery of monoclonal antibodies with direct fluorescent epifluorescence
microscopy (modified DFA). 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. |
We report the number of morphologically intact Legionella that have been associated with human disease in one milliliter of test sample.
We test for 14 serogroups of Legionella pneumophila and 15 other Legionella species associated with human disease;
L. anisa, L. bozemanii serogroups 1 & 2, L. dumoffii, L. feeleii serogroups 1& 2, L. gormanii, L. hackeliae serogroups 1 & 2, L. jordanis, L. longbeachae serogroups 1 & 2, L. maceachernii, L. micdadei, L. oakridgensis, L. parisiensis, L.
sainthelensi, L. santicrucis and L.
wadsworthii.
Our test result of <10/ml (sensitivity of the test) indicates
no observed evidence of legionella in
the sample. This is equivalent to a culture test result of <1/ml if the culture procedure is properly
performed and validated by the DFA monoclonal antibody test.
There
are no government regulations concerning permissible numbers of these bacteria
in water systems. We cannot make
definitive statements about safety of the levels of legionella species in your water-containing system.
If the
count is 200 per ml or greater, or if a review of this and previous reports
shows an increase in numbers of Legionella
per ml, decontamination is indicated.
This is not a routine maintenance procedure. Our recommended decontamination procedures follow the
State of Wisconsin Department of Health guidelines adopted by the CDC and the
US EPA guidelines.
Gilpin
Testing Service and Gilpin Limited assume no responsibility for the safety of
the water system at the time of analysis or for any condition that may arise
thereafter. |
Regular monitoring by trained personnel with a battery of DFA monoclonal antibodies for several serogroups and species of Legionella morphologically intact bacteria provides a means for exercising 'reasonable care' to deter potential litigation. |
Because
of legal liability for us and our customers, we do not use culture
methods found in the 2005 CDC Procedures for the Recovery of Legionella
from the Environment or the Association Francaise de Normalisation
(AFNOR) or the ISO 11731-2:2004 culture membrane method or the UK Health
and Safety Executive Legionella Guidelines or the OSHA Technical
Manual, Section III, Chapter 7, Legionnaires’ Disease Appendix III 7.2
Physical Survey and Water Sampling protocols.
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Detection of Legionella spp. by culture
techniques is insensitive. Overgrowth of culture media with competing
flora is a major problem. Some peer-reviewed papers are cited below:
1) Fields BS, Benson RF, Besser RE. Legionella and Legionnaires' disease: 25 years of investigation. Clin Microbiol Rev. 2002;15:506-26.
2) DOI: 10.1128/CMR.15.3.506-526.2002.
3) Bartram J, Chartier Y, Lee JV, Pond K, Surman-Lee S. Legionella and the prevention of legionellosis. Geneva: World Health Organization; 2007.
4) Parthuisot, N, Binet M, Touron-Bodilis A, Pougnard C, Lebaron P and Baudart J. Total and Viable Legionella pneumophila
Cells in Hot and Natural Waters as Measured by Immunofluorescence-Based
Assays and Solid Phase Cytometry. Applied and Environmental
Microbiology 77:6225-6232, September 2011. |
Culture methods will not identify non-culturable Legionella
that can still cause outbreaks.
Non-culturable, viable legionella have
been reported in several peer-reviewed journals, including Acta
Pathologica, Microbiologica et Immunologica Scandinavica 113:45-53,
2005. The American Academy of Microbiology recommends new approaches
for analyzing uncultivated microorganisms. Only DFA tests performed by
trained laboratory personnel can identify these legionella. |
Heterotrophic bacterial CFU are often inversely proportional to numbers of Legionella
in cooling tower samples, in our experience and experience of others.
(Miller RD and KA Kenepp, Risk Assessments for Legionnaires Disease
Based on Routine Surveillance of Cooling Towers for Legionellae, pp. 40-43. In, Barbaree, JM, RF Breiman and AF Dufour Eds., Legionella: Current Status and Emerging Perspectives, American Society for Microbiology Press, 1993, Washington, DC)
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Europeans have reported that 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). |
Legionnaires' Disease caused by Legionella longbeachae have increased worldwide since the 1980's. All confirmed cases of disease were associated with potting mixes and composts. (H. Whiley and Bentham R. Legionella longbeachae and Legionellosis. Emerging Infectious Diseases 17:579-583, April 2011). |
Genetic typing of Legionella isolates
confirmed cooling towers as likely sources of the 2000 and 2006
outbreaks in Rennes, France in a single mall in Rennes.
"High-Throughput Typing Method To Identify a Non-Outbread-Involved Legionella pneumophila
Strain Colonizing the Entire Water Supply System in the Town of Rennes,
France." D. Sobral, P. Le Cann, A. Gerard, S. Jarraud, B. Lebeau, F.
Loisy-Hamon, G. Vergnaud & C. Pourcel. Applied and Environmental Microbiology 77:6899-6907, October, 2011. |
The U.S. Environmental Protection Agency and the U.S. Occupational Safety and Health Administration recommend routine maintenance of water-containing equipment. GTS recommends monthly testing for Legionella as part of a routine maintenance program. |
