Important Information To Avoid
• Outbreaks and New Construction
With renovation, installation of low flow/electronic
Commissioning process ineffective for Legionella
Long dormant periods (months) before occupying
• CDC ELITE Labs
All are not equal in Legionella testing proficiency
• Cooling Tower Biocides
All are not effective against Legionella
ELITE Certified Labs
Did You Know That Labs
Differ in Their Methods for
Legionella Testing &
“Apples To Apples”
“Apples To Oranges”?
• Processing Methods
Pretreatment (heat and/or acid)
Filtration (yes/no or how much)
Culture media (types and how many)
• Identification (ID) Methods
Only presumptive agglutination test?
Definitive ID with DFA or sequencing for
Testing Can Be Revealing
testing are more likely to
prevent cases of
Squier CL, Stout JE, Krystofiak S, McMahon J,
Wagener MM, Dixon B. Yu VL. Am. J. Infect.
Control 2005; 33(6): 360-367.
Questions to Ask
• Was Legionella found in the water
• Pathogenic species?
• Extent of colonization?
Colonization Rate of >30% (Percent
Positivity) = Increased Risk (Especially if
L. pneumophila serogroup 1 present)
• Colonization in sensitive areas?
TO TEST OR NOT TO TEST?
Evaluating Risk of
Exposure to Legionella
• Initiate environmental
• if >30% sites positive
for L. pneumophila,
surveillance for cases
• If cases identified, then
Approach to Environmental Sampling
• Select a minimum of 10 distal sites
(faucets or showers) that roughly
represent the water distribution system,
plus hot water tanks or recirc. line.
• Include sites on multiple floors and wings,
high risk areas like oncology, transplant
units, medical surgical units.
Calculating Percent Positivity
• Number of OUTLETS positive for
Legionella of 10 distal sites (faucets
or showers) that were tested
• Estimating the probability of a patient
“bumping into” Legionella (Percent
Risk – Potable Water
Risk of Legionnaires’ disease was better
predicted by the
of water system sites
testing positive for Legionella
than by the
concentration of Legionella bacteria.
Kool J L, et al. Infect. Control Hosp. Epid. 1999 20:797-805
Risk Criteria Based on
Environmental Monitoring Results
establish target values
in CFU per liter or
OK for cooling towers
as a performance-
based target (not
• Colonization rate
or proportion of distal
sites in the water
system that are
positive for Legionella
Best for hospitals and
• Legionnaires’ disease is increasing
• Potable Water systems, especially in
hospitals (and other buildings) with
complex hot water systems, are the most
important source of Legionella
• Proactive prevention = ASHRAE 188
Water Management Programs and Risk
• Environmental testing for Legionella is a
key indicator for disease risk
Start Your ASHRAE 188
Water Safety Program
Establish a Plan to Respond Not React