LEGIONELLA - World Health Organization

S te
Approx mate
number of
samples
Volume
of samples
Water source(s) near air intake(s) 4 ≥ 100 ml
Air samples where patients were ill with legionellosis 3 n.a.
Potable water f nal d str but on outlets
Haemodialysis water source
Before or after demineralizer 1 ≥ 1 litre
Intens ve care un ts
Respiratory therapy (patients’ room) 2 1 litre
Cardiac 2 1 litre
Services with different geographical locations 7 1 litre
Ice-maker (entry water) and ice ≥ 1 litre
A r-cond t on ng system
Air handling unit serving area where disease occurred 2 ≥ 100 ml
Cooling towers
Return from heat exchanger to water (spray/trough
and gutter) distribution or pond (sump)
2 ≥ 1 litre
Water supply 1 1 litre
Hot tubs
Pool and balance tank (if fitted) 1 1 litre
Jets and pipes 1 Swab
Other
Decorative fountain 1 1 litre
Creeks, ponds, sites of stagnant water 4 >1 litre
n.a. = not applicable
Source: Adapted from Barbaree et al., 1987
11.4.4 Collecting environmental samples
Two primary sample types — water samples and swabs of point-of-use devices or system
surfaces — should be collected when sampling for legionellae. Collection of at least 1 litre of
water allows the sample to be concentrated, if necessary. If the water source has recently been
treated with an oxidizing biocide, such as chlorine or bromine, sodium thiosulfate must be added
to each 1-litre sample in sufficient quantities to neutralize any disinfectant present. Depending
on the reason for sampling, the sample may be taken as a first flush (i.e. no disinfection). This
is appropriate for most occasions and will represent the worst case. After disinfection, the
sample will be taken from a running outlet representing the circulating system.
0 LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS