Premi®Test - for the detection of antimicrobial substances in eggs

Background

Using egg fluids in a microbial inhibition test may result in false positive results due to the presence of several naturally occurring inhibitors in egg yolk. To prevent these inhibitors interfering with the test result a special protocol is required to use the Premi®Test for the detection of antibiotic residues in eggs. Therefore DSM has developed a proprietary technology. This patented technology is described in this technical bulletin. The influence of naturally occurring inhibitors can easily be prevented by inactivating the proteinaceous factors in eggs through a short heat pre-treatment step of the egg fluid.

1. Sample preparation method

1. Wash hands before use and make sure to use a clean working surface.
2. Make a hole of approximately 1-2 cm in the egg.
3. Prick into the egg yolk, so the yolk will flow out of the egg easier with the egg white.
4. Place the egg with the hole down on a clean bottle.
5. After the egg is empty, close the bottle.
6. Homogenize the egg fluid by shaking the bottle for several seconds.

2. Instructions for using Premi®Test

1. Remove the aluminum foil carefully from the ampoule(s).
2. Use a clean pipet tip on the syringe: Cut a small part from the pipet tip to avoid blocking.
3. Transfer 100 µl of homogenized egg fluid onto the agar in the ampoule, by pressing the syringe once and releasing it. It will automatically take up the required volume.
4. Close the ampoules with the plastic foil supplied with the kit.
5. Place the ampoule(s) in the Premi®Test 2-Step Incubator and push the “program” button, as described in the instructions of this Incubator.
6. The Premi®Test 2-Step Incubator automatically heats the samples for 10 minutes at 80°C.
7. After this heat pre-treatment, the Premi®Test 2-Step Incubator incubates the samples at the required temperature of 64°C (± 0,5 °C).
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8. Incubate the sample until the negative control (egg fluid what has been tested before negative) changes color.

3. Reading the test results

1. When the negative control changes color from purple to yellow (approx. 3 hours), the results can be red. 
2. Read the results from the bottom 2/3 part of the ampoule.
3. A clear color change purple to yellow indicates that the antimicrobial compounds are below the Premi®Test detection limits.
4. A purple color indicates  the presence of antibiotics at or above the detection limits of the Premi®Test.

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