3M environment Listeria test strip operation and interpretation

3M environment Listeria test strip operation and interpretation
First, the test environment Listeria number operation method
1. Store unopened test pieces in <= 8 oC (46 oF) and use them within the expiration date indicated on the package. In high humidity areas, it is best to return the test piece to room temperature before use.
2. The opened test piece, reflexed the opening and sealed with tape.
3. To prevent exposure to moisture, do not refrigerate the opened test piece. The test piece sealed with the tape is stored in a low-temperature and dry place for a period of not more than one month. Do not place the test piece in an environment with a temperature > 25 oC (77 oF) and/or a relative humidity > 50%.
4. Collect environmental samples with a stick, sponge or other sampling device. The liquid of the wet sampling device should be <= 10 mL. The humectant can be sterile water, Buffered Peptone Water (BPW), or a neutralization buffer such as Letheen Broth or Dey/Engley (DE) Neutralizing Broth.
5. Add 5 mL, 20-30oC, sterile buffered buffered water (BPW) solution to the collected sample in a sterile environment. Do not share Petrifilm EL test strips with Vermont medium (UVM), Fraser broth, Listeria enrichment medium (LEB) or Listeria monocytogenes (BLEB).
6. Mix, wriggle or rotate the mixture of sample and BPW for approximately one minute. The sample is placed at room temperature (20-30 oC) for 1 h and no longer than 1.5 h for repairing the damaged Listeria.
7. Place the test piece on a flat surface and uncover the upper film.
8. Using a 3MTM electronic pipette or other pipette, add 3 mL of the sample vertically to the center of the lower membrane.
9. Slowly cover the upper film to avoid air bubbles.
10. Gently place the plastic platen on the upper film on the inoculation area. Do not press, twist or slide the platen. Lift the platen. Wait at least 10 minutes for the colloid to solidify.
11. Place the test piece with the transparent side facing up and stack it up to 10 pieces and incubate at 35oC ± 1oC or 37oC ± 1oC for 28h ± 2h.
12. Petrifilm EL test strips can be counted or interpreted using standard colony counters or other optical amplifiers. Do not count colonies on a circular outline as they are not affected by selective media.
Petrifilm EL test strip method for qualitative, semi-quantitative and quantitative detection
Not detected
13. For qualitative testing, the results are counted as detected and not detected based on the presence or absence of purple colonies.
If the result of yes/no is enough to meet the reporting requirements, then you can choose qualitative testing.
14. For semi-quantitative testing, record the results based on the relative amount of purple-red colonies. If you take the appropriate measures based on the relative amount of colonies and there is no need to record the actual number of colonies, then you can choose semi-quantitative testing. Listeria monocytogenes should be recorded as instructive for sampling areas and corporate standards (eg low, medium, high, or acceptable and unacceptable)
15. For quantitative testing, count all purplish colonies. If you take the appropriate measures based on the number of colonies, you can use quantitative testing. Number of Listeria on the test piece: 16
Please refer to the “Quantitative Sampling and Interpretation” section of the Interpretation Manual to calculate the number of Listeria in each environmental sample.
16. Colonies can be picked for further identification. Pick up the upper membrane and pick up the colony from the gel.
Quantitative sampling and interpretation
If you use 3M Petrifilm EL test strips in a quantitative manner, please refer to the product's package insert and calculate the number of colonies per unit area (CFU) as follows. At the same time, you should also pay attention to the following points:
1. Stability is a key point in obtaining useful information during environmental monitoring, so the same steps should be used during the sampling process. Ideally, the same type of sampling equipment, template area, technician and sampling technique should be used.
2. The size of the sampling area can be set according to regulations, internal standards, and/or monitoring locations. For example, considering the lower number of bacteria, a larger sampling area should be used for the finished line.
3. For more information on environmental sampling, please see the references below, or refer to the 3M Petrifilm Test Strip Environmental Monitoring Manual.
In order to determine the number of Listeria in a unit sampling area, you need to record the following data:
Sampling area
2. The amount of liquid in the wet sampling device
3. Add buffer protein to the volume of water
4. Inoculation volume
5. Number of Listeria on the test piece
Use the following equations and tables to calculate the number of colonies per unit of sample area (CFU/area sampled). See the next page for an example. See the package plugin and operating instructions for details on the method.
You can also measure the results of a unit sample, such as CFU / per discharge
or
Environmental quantitative sampling meets the following literature:
Standard Methods for the Examination of Dairy Products, Section 3.7D, American Public Health Association, Washington DC, 1992.
Compendium of Methods for the Microbiological Examination of Foods, Section 3.512 and 3.521, American Public Health Association, Washington DC, 2001
Quantitative interpretation
1. Dip the sponge with 10 mL of liquid and apply the sample surface as 1 square foot (1 ft2).
2. Place the sponge back into the sterile container and add 5 mL of Buffered Protein Water (BPW).
3. After the repair is complete, pipette 3 mL of the mixture into the Petrifilm EL test piece.
4. After the culture, colony counts are performed (in this example, the number of colonies is assumed to be 90).
1. Wet the applicator with 1 mL of liquid and apply the sample surface, such as an area of ​​50 cm2 (50 cm2).
2. Place the applicator stick back into a sterile container and add 5 mL of Buffered Protein Water (BPW).
3. After the repair is complete, pipette 3 mL of the mixture into the Petrifilm EL test piece.
4. After culture, colony counts are performed (in this case, if the number of colonies is 90).
Second, the test environment Listeria method
The 3MTM PetrifilmTM Environmental Listeria (EL) test strip is a pre-prepared medium containing selective reagents, nutrients, cold water soluble gels and a color indicator that aids in colony detection. Petrifilm EL test strips can be used to detect or count the number of Listeria in environmental samples. Listeria detected by Petrifilm EL test strips including L. monocytogenes L. innocua, L.grayi/murrayi, L. welshimeri, but cannot distinguish between various bacteria.
Environmental conditions and disinfectants may inhibit or damage microorganisms. Buffered Peptone Water (BPW) can be used in combination with repair broth and Petrifilm EL test strips. However, the repair process of Listeria in buffered peptone buffer is not an enrichment step.
1. Figure 1 shows a typical Petrifilm EL test strip with Listeria. Interpret or count all purple-red colonies as Listeria. If there are gray or light pink colonies in the 26-29 hours, continue to culture. During the culture time, colonies that are darkened by gray or pale pink to purplish red should be judged as Listeria. Colonies that remain gray or pale pink at maximum incubation time (30 hours) should not be interpreted as Listeria. Colonies on a circular outline are not considered or counted because they are not affected by selective media.
Qualitative interpretation: The test piece detected Listeria.
Semi-quantitative interpretation: Listeria monocytogenes should be recorded in a form that is instructive for sampling areas and corporate standards (eg, low, medium, high, or acceptable and unacceptable).
Quantitative interpretation: Listeria number on the test piece: 11.
Please refer to the “Quantitative Sampling and Interpretation” section of the Interpretation Manual to calculate the number of Listeria in each environmental sample.
2. The Petrifilm EL test piece had no colony growth after 30 hours of culture, and the experiment was over.
Qualitative interpretation: Listeria was not detected on the test piece.
Semi-quantitative interpretation: Listeria monocytogenes should be recorded in a form that is instructive for sampling areas and corporate standards (eg, low, medium, high, or acceptable and unacceptable).
Quantitative interpretation: Listeria number on the test piece: < 1.
Please refer to the “Quantitative Sampling and Interpretation” section of the Interpretation Manual to calculate the number of Listeria in each environmental sample.
3. Petrifilm EL test strips are selective for Listeria and their colonies are shown in purplish red.
Qualitative interpretation: Listeria was detected on the test piece.
Semi-quantitative interpretation: Listeria monocytogenes should be recorded in a form that is instructive for sampling areas and corporate standards (eg, low, medium, high, or acceptable and unacceptable).
Quantitative interpretation: Listeria number on the test piece: 84.
Please refer to the “Quantitative Sampling and Interpretation” section of the Interpretation Manual to calculate the number of Listeria in each environmental sample.
4. Since there are three ways to interpret Petrifilm EL test strips, there is no recommended count range. When colonies are dense, qualitative or semi-quantitative results are interpreted as follows, or quantitative results are estimated.
Qualitative interpretation: Listeria was detected on the test piece.
Semi-quantitative interpretation: Listeria monocytogenes should be recorded in a form that is instructive for sampling areas and corporate standards (eg, low, medium, high, or acceptable and unacceptable).
Quantitative interpretation: Estimated number of Listeria on the test piece: approximately 460. When a large number of Listeria is present, it is estimated by counting the number of colonies of two or more representative squares. Calculate the average number of colonies per square and multiply by 42. The inoculation area of ​​the Petrifilm EL test piece was approximately 42 cm2.
5. When the number of colonies is large, there may be many small, unclear colonies on the test piece, and/or all pink to brown.
Qualitative interpretation: Listeria was detected on the test piece.
Semi-quantitative interpretation: Listeria monocytogenes should be recorded in a form that is instructive for sampling areas and corporate standards (eg, low, medium, high, or acceptable and unacceptable).
Quantitative interpretation: The number of Listeria on the test piece is Too Numerous To Count (TNTC). The number of colonies in this figure is approximately 104.
6. The background color may change due to dust, dirt, sand, or other deposits in the environmental sample, or it may be caused by different brands of sampling equipment and/or buffered protein (repair fluid). The purple-red colony was interpreted as Listeria.
Qualitative interpretation: Listeria was detected on the test piece.
Semi-quantitative interpretation: Listeria monocytogenes should be recorded in a form that is instructive for sampling areas and corporate standards (eg, low, medium, high, or acceptable and unacceptable).
Quantitative interpretation: Listeria number on the test piece: 11.
Please refer to the “Quantitative Sampling and Interpretation” section of the Interpretation Manual to calculate the number of Listeria in each environmental sample.

AM Detector

Eas anti-theft antenna is mainly suitable for large supermarkets, shopping malls, bookstores, audio stores with Security hard tags, rf soft label, AM lable,Pin and Lanyard, eas detacher, Hook Lock,EAS Self Alarm Tag, EAS Safer Box,etc.

WENZHOU BOSHINE ELECTRONIC SECURITY CO.,LTD , https://www.cnboshine.com