Sampling Method Microbiological Testing | Microbiological Sampling Method

To lay down the procedure for sampling method for micro testing. There are 4 basic methods for sampling methods for micro testing enumerating micro-organisms on surfaces, the swab-rinse, the rinse, the agar contact, and direct surface agar plating. Numerous other methods that have been described in the literature are mainly modifications of these techniques.

Procedure Sampling methods Microbiological testing

A 500ml sample in a sterilized plastic bottle is required for this analysis (sterilized bottles are provided by the laboratory on request).

Samples should be taken at the supply and at various taps in the distribution system (see sampling techniques below).  All samples must be chilled to 4°C (except those to be analyzed for Amoeba) and should arrive within 24 hours of collection. Label each bottle with the Location, Date, and Time.

Do not rinse the sample bottle before sampling.

The cap of the bottle should not be placed lid down at any point nor should fingers come into contact with the underside of the lid.

It is helpful to leave small air space in the bottle to facilitate mixing by shaking before the examination

Microbiological sampling Method

Taps. When sampling from a tap, open it fully and let the water run to waste for 2-3 minutes or for a time sufficient to permit the clearing of the service line. Reduce the flow to permit filling the bottle without splashing. 

If tap cleanliness is questionable apply a solution of Sodium Hypochlorite (100mg/L) or flame the faucet before sampling. Let the water run for an additional 2-3 minutes after treatment. 

If sampling from a hot/cold tap, run hot water for 2 minutes then cold water for 2-3 minutes, and collect samples as above. 

Reservoirs (e.g.: Tanks, Swimming Pools, Cooling Towers, etc) Hold the closed bottle near its base and plunge it below the surface. 

Remove the top and turn the bottle until its neck points slightly upward and the mouth is directed toward the current. 

If there is no current, create one by pushing the bottle forward away from the hand. 

Replace the cap before pulling the sample out.