Description

Enumeration of micro-organisms: bacteria, fungi and yeasts

To determine the level of pollution by micro-organisms in a sample, the following procedure is followed:

Aqueous sample: 0,1 ml of water is spread on Petri dishes.
Oily sample: oil, fuel, lubricants: 2 ml of the sample is emulsified in 18 ml of a Tween 80 solution. Then 0.1ml of emulsion is spread on Petri dishes. This method is covered by a Qualification Certificate for Special Processes from SAFRAN Laboratories N° AQPS 490.
surface sampling: using a swab previously soaked in diluent or a dry swab, depending on the surface, take the sample by squaring an area estimated to be between 20 cm³ and 100 cm³. The swab should be turned between thumb and forefinger, making ridges perpendicular to each other. Return the swab to the tube with diluent if necessary.
Depending on the micro-organisms to be tested, the agar will be adapted. The swab is spread on the agar in a grid pattern, while rotating the swab.