Environmental Sampling for the Detection of Microorganisms

Laboratory Procedure MFLP-41A
September 1992

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Health Protection Branch
Ottawa

1. Application

This method is applicable to the sampling of the environment in food establishments in support of compliance activity relative to Section 7 of the Food and Drugs Act. The sampling includes, but is not restricted to, equipment and food contact surfaces. It describes the procedures to be used for the collection and handling of environmental samples for microbiological assessment.

2. Principle

The presence of pathogens or of high numbers of bacteria in the environment of food establishments may indicate poor sanitation or microbial growth niches. This method estimates the number or presence of viable microorganisms removed from a defined sampled surface. Samples obtained are then inoculated into or onto selective media, specific to the microorganism(s) of interest. It is assumed that each viable microorganism will multiply under these specified conditions of incubation in media and give rise to visible growth which can be measured, counted and identified. This method is still considered semi-quantitative since there is very little relationship between the number of colonies found on the agar and the actual number of viable cells that are present on the surface being sampled. However, identification of microorganisms isolated may provide valuable information.

3. Background

Environmental sampling for the detection of microorganisms was first used by the Health Protection Branch during the seventies to investigate Salmonella contamination in milk powder plants. It can be used to determine the presence of pathogens as well as indicator microorganisms (e.g. coliforms) on equipment and food contact surfaces. It is now recognized that bacteria can grow on food contact surfaces and may form biofilms which are very difficult to remove during cleaning operations.
Microbiological results of environmental sampling can be used by inspectors to document deviations from good manufacturing practices for enforcement purposes and as an educational tool to convince plant management where corrective measures are needed. It is important that a proper and common technique be used by Health Protection Branch inspectors across the country to maintain uniformity.

4. Collection Of Samples

Before commencing the environmental sampling, the person responsible should take the following steps:

- Draw a process flow chart and plant traffic pattern;

- Determine target organism(s) or hazards;

- Identify the critical control points;

- Determine sampling sites;

- Arrange with laboratory personnel for sterile equipment and sterile material; and

- Identify material and record according to sampling sites.

Aerobic colony count and coliform enumeration are most often used to assess overall sanitation. If information is needed regarding cleaning and sanitation conditions in the plant, it is recommended that samples be taken immediately before production just after cleaning and sanitation have been completed. If information is needed regarding the microbiological environmental conditions during production, it is recommended that samples be taken during production.

5. Materials and Special Equipment

5.1 Sterile equipment¹:

1) Spoons (short and long handles)
2) Forceps
3) Knives (Victorinox (local supplier) or equivalent)
4) Plastic cups (8 oz., Becton Dickinson Labware, #4015, or 10 oz. Georges Gagné and ass.², or equivalent)

5) Cotton swabs
6) Pre-moistened sponges, J-cloths, gauze or cloths in Nalgene jars
7) Disposable overalls, head cover, overshoes, facial hair-cover³ (if sterile clothing is needed)
8) Prepackaged surgical gloves⁴ (wrist)
9) Sleeves
10) Whirlpak™ bags
11) RODAC plates
12) Petrifilm™ plates (pre-m 13) Polypropylene containers (Nalgene or equivalent)
14) Appropriate nutrient media

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¹Each sterile package should be marked with an expiry date

²Georges Gagné and ass., 784 Prom. Iroquois, Cornwall, Ontario, K6H 5C5 (Tel: 613-933-6050)

³(Kimberley-Clark Canada Ltd., 365 East Bloor St. Toronto, Ont., M4W 3L9, (Tel: 1-800-361-5876)

⁴Becton-Dickinson, Tru-Touch, Stretch Vinyl, Medical Gloves, Single Use