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  • Pilar G. Burkhard

Legionella Testing Method Comparison

Most of our customers request the CDC method due to its looser restrictions regarding hold times and temperature requirements. The ISO 11371 method has stricter requirements for sample receiving, along with a more in-depth procedure. Samples may still be processed if they do not meet the requirements, per the analyst’s discretion, with the reason noted on the report. Below is a guide to help decide which method best meets your testing needs.


Legionella Isolation and Identification Method Comparison

CDC ELITE

ISO 11371

SAMPLE VOLUME

250 mL is acceptable for routine testing. 1 liter is recommended for potable samples.


1 liter is required for an outbreak investigation.*

250 mL is acceptable for routine testing. 1 liter is recommended for potable samples.

HOLD TIME

72 hours

48 hours

TEMPERATURE UPON RECEIVING

Ambient is acceptable, but samples should be refrigerated if not processed within 24 hrs.

5°C ± 3°C, OR ambient if received within 24 hrs.

SAMPLE PROCESSING

​Non-potable samples are directly plated on agar suitable for Legionella growth.


Potable samples are filter concentrated before plated on agar suitable for Legionella growth.

​Non-potable samples are plated on agar suitable for Legionella growth.


Potable samples are filter concentrated before plated on agar suitable for Legionella growth.


All samples are processed in duplicate with and without pretreatment.

LEGIONELLA CONFIRMATION

​Any colonies suspected of being Legionella are confirmed by subculture.

​Any colonies suspected of being Legionella are confirmed by subculture.

LEGIONELLA IDENTIFICATION

Latex Agglutination

Latex Agglutination

* Unless otherwise specified, the CDC ELITE method is the preferred method for an outbreak investigation





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