Legionella spp. – Swab

Consistent with O. Reg. 671/92 of the French Language Services Act, laboratory testing information on this page is only available in English because it is scientific or technical in nature and is for use only by qualified health care providers and not by members of the public.

This page provides environmental microbiology testing information for the Legionella spp. – Swab analysis available at Public Health Ontario (PHO).

This test information sheet now consists of additional details on the algorithm and interpretation of Legionella spp. swab analysis.

Testing Indications

Acceptance/Rejection Criteria

Refer to the Public Health Inspector’s Guide to Environmental Microbiology Laboratory Testing.

Specimen Collection and Handling

Specimen Requirements

Test Requested Required Requisition(s) Specimen Type Minimum Volume Collection Kit

Legionella spp.– Swab1

Environmental swabs


Requisition for Specimen Containers and Supplies form

Sterile environmental swabs, record “Environmental swabs” and quantity required on the comment section of the form

Submission and Collection Notes


This analysis is available for investigations and/or outbreaks with a confirmed clinical case(s) of Legionella.


Use the Environmental Microbiology Investigation Requisition Form (07/2019 version, or newer) and ensure all mandatory fields on the form are completed, including Legionella as the confirmed etiological agent.

Storage and Transport

Samples should be stored at refrigeration temperature (2 to 8°C) and shipped to the laboratory as soon as possible.

Special Instructions

For sampling instructions, refer to the Public Health Inspector’s Guide to Environmental Microbiology Laboratory Testing.

Shipping Instructions:                

  • Ship swab samples in containers with hard walls and lids secured in the closed position.
  • Shipping containers must be labelled with the submitting organization, unique identifier and contents e.g., SWAB SAMPLES on the outside of the container.
  • DO NOT SHIP WITH CLINICAL SPECIMENS. Shipping containers used for swab samples should be dedicated to swab samples.
  • Ship swab samples in an insulated container with sufficient cold packs to maintain a temperature of 2 to 8°C. If ice is used, contain the ice in a manner that does not allow water contact with the samples.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Legionella spp. testing is performed Monday to Friday at PHO’s Toronto laboratory. Upon receipt at PHO’s Toronto laboratory, the turnaround time for culture is up to 14 business days. Additional time may be required for confirmation testing, where applicable.

Test Methods

PHO’s laboratory analyzes environmental swab samples using a modified Centers for Disease Control and Prevention culture methodology. The presence of Legionella spp. on the environmental swab is determined by the culture method by isolation of the bacterial filtrate on selective agar plates, followed by biochemical and serological identification. Results are reported as Detected with the specific Legionella spp. or Not detected, as appropriate.


The following table provides possible test results with associated interpretations for Legionella culture testing:  

Result Interpretation Comments
Not Detected Viable Legionella did not grow on the bacteriological medium. Note: the presence of other non-Legionella bacteria in the environment may also mask the presence of the Legionella.
Detected Viable Legionella did grow on the bacteriological medium.  

Results must be interpreted within the context of the clinical, environmental, epidemiological and laboratory information/data.


Results are reported to the submitter (e.g., Board of Health) as indicated on the requisition.


  1. Public Health Ontario. Public Health Inspector’s Guide to Environmental Microbiology Laboratory Testing [Internet]. Evergreen ed. Toronto, ON: King’s Printer for Ontario, current version [cited December 29, 2023]. Available from: Public Health Inspectors Guide
  2. Biotecon Diagnostics. microproof® Legionella Quantification LyoKit – 5´Nuclease – . [Internet]. Germany, 01/2020 [cited December 29, 2023]. Available from https://cms.hygiena.com/sites/default/files/media/KIT230119-120_Legionella_Quantification_LyoKit.pdf
  3. U.S. Department of Health and Human Services. CDC Laboratory Guidance for Processing Environmental Samples. Atlanta, GA: Centers for Disease Control and Prevention (CDC), reviewed April 30, 2018 [cited December 29, 2023]. Available from https://www.cdc.gov/legionella/labs/procedures-manual.html
  4. Government of Canada. Mechanical Design 15161—2013: Control of Legionella in Mechanical Systems. [Internet]. Ottawa, ON, modified: August 31, 2022 [cited December 29, 2023]. Available from: https://www.tpsgc-pwgsc.gc.ca/biens-property/legionella/index-eng.html
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Updated 31 Jan 2024