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Public Health Inspector's (PHI's) Guide – Environmental Swabs

Environmental swab testing is performed to support foodborne illness outbreaks and investigations. This section provides information for public health inspectors (PHIs) when submitting environmental swabs to Public Health Ontario laboratory (PHOL) for testing.

Contents

Swab – Microbiological Analysis Test Menu

PHOL performs microbiological testing of environmental swabs to support foodborne outbreak investigations or for R.R.O. 1990, Reg. 562: Food Premises, Section 80 as outlined below. 

The standard plate count from a multi-service article shall not exceed 100 bacterial
colonies after cleaning and sanitizing and prior to re-use when tested by an official
method in accordance with the standard plate test, utilizing the swab technique.
R.R.O. 1990, O. Reg. 562, s. 80

 

 


 

 

Standard Plate Count (SPC) results are obtained from the Aerobic Colony Count (ACC) method
performed by PHOL. SPC and ACC are name variations of the same test method. 

Environmental swabs processed during foodborne outbreak investigations will be tested for the
presence or absence of a specified clinically confirmed bacterial pathogen from a physical environment
(e.g., cutting board, meat slicer, etc.).

Sampling instructions for environmental swabs are provided below. Test information including testing
frequency, turnaround times and reporting limits, is dependent on the specific analysis.
Click on individual testing links for test directory details:

Sample Selection

Instruction for sample selection of sanitation swabs:

Select items (e.g., cup, plate and/or utensils) for testing of a typical sanitation cycle run (i.e., routine cycle on dishwasher) or surfaces.

 

 

 

Instruction for sample selection of swabs for an outbreak investigation:

To identify the source of the pathogen, selection of sampling sites for the investigation should be informed by environmental and epidemiological factors. Random sampling may delay the identification of the source of the outbreak. Samples deemed as most likely to be positive should be sampled and submitted first.

 

 

 

 

 

PHOL should be notified prior to sample submission to allow for preparation of materials required for testing. Please contact the laboratory by calling PHOL Customer Service Centre at 416-235-6556 or toll free 1-877-604-4567.

Containers for Sampling

Instructions

  • Environmental swabs are available from the PHOL warehouse and can be ordered by calling the
    PHOL Customer Service Centre at 416-235-6556 or toll free 1-877-604-4567. The swab vial
    contains neutralizing solution as transport medium. This medium can neutralize quaternary
    ammonium compounds and phenolic disinfectants.
  • Refer to the test directories Aerobic Colony Count (swab) or the specific foodborne pathogen test
    directories, i.e., Salmonella spp. , Listeria monocytogenes or E. coli O157:H7 for additional details.
  • Each sample and its accompanying requisition must be labeled with a unique identifier.

Sample Preparation

The following steps are recommended to organize and minimize sample collection time:

  • Investigate before sampling to determine a sampling plan.
  • Ensure all materials required are available prior to collection.
  • Label sample container using a permanent marker.
  • Complete requisition(s) before or after, never during, sample collection.
  • After collection, double check to ensure the sample unique identifier on the sample container and requisition are legible and match.

Sample Collection

Instructions

  • Using aseptic technique, open the sterile swab container; grasp the handle end of the swab.
  • Remove the swab aseptically being careful not to touch any portion that might be inserted into the vial.
  • Moisten the swab head and press out the excess solution against the interior wall of the vial with a rotating motion.
  • Hold the swab handle to make a 30 ° angle contact with the surface. Rub the surface slowly and thoroughly over approximately 50 cm2 of the surface three times, reversing direction between strokes.
  • After the area has been swabbed, using aseptic technique, return the swab to the vial.
  • Complete all sections of the Environmental Bacteriology Swab Tests requisition with appropriate information to ensure accurate tracking of sampling. If the swab was collected due to a foodborne illness outbreak investigation, check “Other analysis” and record the pathogen, e.g., Listeria monocytogenes, in the same area.
  • Ensure samples are submitted to the laboratory under refrigeration conditions (2 – 8 °C) in a manner that will not leak during transport.

Considerations

  • Leaking swab vials will be rejected by the laboratory. Ensure the vial is closed tightly to prevent leakage resulting in sample rejection.
  • Absence of a unique identifier linking sample(s) to a sampling location on a requisition will result in rejection of sample(s) by the laboratory.
  • For an investigation where sampling areas are smaller and physically different, a new swab should be used for each different area. If the sample area is large, multiple sections may be swabbed with one swab.
  • For sanitation testing, swabs received at greater than 10 ° C will be subject to rejection.

Environmental Swab – Laboratory Acceptance Criteria

The accuracy of the test results may be affected by improper collection, handling and/or shipping. Swab samples that do not meet the acceptance criteria may be rejected by the laboratory and a new sample may be re-submitted with a newly completed requisition. The acceptance criteria are outlined below.

​Description ​Acceptance Reason
​Submitter
  • ​Swab samples must be received from an authorized board of health submitter.
​Sample Type
​Sample Requisition
  • ​The requisition must be completed when it is received at the laboratory, including date and location of collection. If a sample is received without a requisition it will not be processed; however, the sample will be held for 24 hours.
  • The requisition must have a unique identifier that matches the unique identifier on the swab collection vial.
​Sample Collection
  • ​Environmental swabs are available from the PHOL warehouse and can be ordered by calling PHOL Customer Service Centre at 416-235-6556 or toll free 1-877-604-4567. Unapproved swabs will not be accepted.
​Sample Transport
  • ​The sample container must be secure to avoid leaks during transport.
  • The sample temperature must meet the requirements listed below when received at the laboratory:
    • Swabs should be shipped with cold packs to maintain a temperature between 2.0 to 8.0 °C during transport to the laboratory.
    • Swabs received frozen or greater than room temperature may be rejected and not processed.

Environmental Swab – Reporting and Interpretation of Environmental Microbiological Test Results

The following tables outline the reporting limits and interpretation of the environmental swab analyses.
Information such as collection conditions, time and date, and sanitation details should be considered
when interpreting swab results.

INDICATOR BACTERIA

​Testing Type ​Reporting Limit (count per vial) ​Unsatisfactory Level (count per vial)
(Standard plate count)

 

​< 10 to > 2.0 x 103

​> 100

High Aerobic Colony Count on the article or surface indicates inadequate sanitation. According to R.R.O. 1990, Reg. 562: Food Premises , Section 80, the standard plate count from a multi-service article shall not exceed 100 bacterial colonies after cleaning and sanitizing and prior to re-use when tested by an official method in accordance with the standard plate test, utilizing the swab technique.8

FOODBORNE PATHOGENS

​Testing Type Reporting Limit​ ​Unsatisfactory Level
Escherichia coli O157:H7 ​Not Detected / Detected ​Detected
Listeria monocytogenes ​Not Detected / Detected ​Detected
Salmonella species ​Not Detected / Detected ​Detected

Foodborne pathogens should not be detected from a ready-to-eat food preparation surface swab and
would indicate poor food handling, inadequate work surface sanitation practices or possible
contamination from an ill food handler. Appendix C: Major Foodborne Diseases: General Features
provide additional information regarding the organisms incubation period, clinical symptoms, mode of
transmission and associated foods.

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Page last reviewed:
Page last updated: 12/10/2017 11:00 AM
Uncontrolled print copy. Valid only on day of Print: [date]
Page updated on [date/time] 12/10/2017 11:00 AM
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