CAROLINA ® Teamed with Teachers 82-4000 3M™ Petrifilm™ Aerobic Count Plates Instruction Manual
Description The 3M™ Petrifilm™ Aerobic Count (AC) Plate is a ready-made culture medium system that contains nutrients, a cold-water-soluble gelling agent, and an indicator dye that makes colonies easier to see. Petrifilm plates are manufactured with a grid background to facilitate counting colonies.
Figure 1 Directions for Use Use sterile technique when handling Petrifilm plates. Disinfect the work area by wiping throughly with alcohol or other disinfectant before and after use. Used Petrifilm plates may contain viable organisms. Do not open the plates unnecessarily. Method A. Inoculation with liquid sample 1. If a Petrifilm plate pack has been stored in the refrigerator, let the package come to room temperature before opening it. This step prevents condensation from forming inside the package. 2.
3. With pipet perpendicular to the Petrifilm plate, place 1 mL of sample onto the center of the bottom film (fig. 3). If necessary, samples can be diluted with distilled water, liquid culture medium, or buffers with pH between 6.6 and 7.2.* If antibiotics are to be added to the medium, add them to the inoculating liquid at the working concentration. Figure 3 4. Release the top film. Allow it to drop onto the bottom film. Do not roll the top film down (fig. 4).
. Hold the spreader with the circular ridge down (flat side up). Place the spreader on the top film over the inoculum (fig. 5). Figure 5 6. Gently apply pressure on the spreader to distribute the inoculum over a circular area. Do not twist or slide the spreader (fig. 6). Figure 6 7. Lift the spreader. Wait at least one minute for the gel to solidify (fig. 7).
8. Incubate plates with the clear side up in stacks of up to 20 plates. Incubation time and temperature will vary according to the application and equipment available. 9. Colonies on Petrifilm plates can be counted on a standard colony counter or other light source (fig.8). Bacterial colonies on Petrifilm AC plates are red because of the indicator dye in the medium. Figure 8 Figure 9 10. Colonies may be isolated for further study or to inoculate additional cultures.
2. Lift the spreader. Wait at least 2 hours for the gel to solidify (fig. 10). Figure 10 3. Hydrated Aerobic Count plates can be stored in the refrigerator in a sealed bag for up to 14 days before use. 4. To inoculate the medium, lift the top film. The circular gel area will adhere to the top film (fig. 11). Hydrated Petrifilm can be used in many ways: • Streak for isolated colonies with a sterile loop, more gently and with less pressure than you would a standard plate.
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