CAROLINA ® Teamed with Teachers 82-4020 3M™ Petrifilm™ E.
Description The 3M™ Petrifilm™ E. coli/Coliform Count (EC) Plate is a ready-made culture medium system designed to facilitate counting coliforms and E. coli. Petrifilm EC Plates contain nutrients, a cold-water-soluble gelling agent, and indicator dyes. Petrifilm plates are prepared on a grid background to facilitate counting colonies. Petrifilm EC plates are designed to allow organisms to grow in an oxygenlimited environment.
Storage Refrigerate unopened packages at ≤8˚C (≤46˚F). Use before expiration date on package. To seal an opened package, fold the end over and tape it shut (fig. 1). Figure 1 Keep resealed packages at room temperature and less than 50% relative humidity. Do not refrigerate opened packages. Use plates from the opened package within one month after opening. Directions for Use Use sterile technique when handling Petrifilm plates.
2. Place the Petrifilm plate on a level surface, with the gridded side down. Lift the top film (fig. 2). Figure 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.
4. Roll the top film onto the bottom film. Do not drop the top film down (fig. 4). Figure 4 5. With the flat side down (not the side with the circular ridge), place the spreader on the top film over the inoculum (fig. 5). Ridge 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).
7. Lift the spreader. Wait at least 1 minute for the gel to solidify (fig. 7). Figure 7 8. Incubate plates with the gridded side down 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 EC plates are red or blue because of the indicator dyes in the medium.
10. Colonies may be isolated for further study or to inoculate additional cultures. Lift the top film and pick the colony from the gel. The medium will adhere to the top film (fig. 9). Figure 9 11. Disinfect before disposal. Petrifilm plates can be disinfected by autoclaving or by soaking in 20% bleach for 1 hour. Then, they can be placed in the trash. Alternatively, they can be taken to a facility such as a hospital or given to a school nurse for disposal with other biohazardous material.
4. To inoculate the medium, lift the top film. The circular gel area will adhere to the top film (fig. 10). Tape the Petrifilm plate to a flat surface in the open position for streaking. Streak with a sterile inoculating loop more gently and with less pressure than you would use on a standard agar plate. Figure 10 5. Incubate the plates with the gridded side down, in stacks of up to 20 plates. Colonies may be isolated for further study or to inoculate additional cultures.
Petrifilm EC plates appear red with no gas bubbles, coliform colonies appear red with gas bubbles, and E. coli colonies appear blue with gas bubbles. Sometimes gas bubbles are trapped when the inoculate is spread on Petrifilm plates. These bubbles are irregularly shaped and not associated with a bacterial colony, while gas bubbles produced by lactose-fermenting bacteria are associated with a colony (see fig. 11.) Figure 11.
To order call: 1-800-334-5551 (US and Canada) 336-584-0381 (International) For technical help call: 1-800-227-1150 www.carolina.
