Carolina 3M Petrifilm Coliform Count Plates User Manual

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3M™ Petrifilm™Coliform

Count Plates

Instruction Manual

CAROLINA

®

Teamed with Teachers

Description

The 3M™ Petrifilm™ Coliform Count (CC) Plate is a ready-made culture
medium system designed to facilitate counting coliforms. Petrifilm CC Plates
contain nutrients, a cold-water-soluble gelling agent, and an indicator dye.
Petrifilm plates are prepared on a grid background to facilitate counting
colonies.

Petrifilm CC plates are designed to allow organisms to grow in an oxygen­limited environment. Their system of nutrients and dyes enables the user to
identify colonies formed by coliforms. For more information, please see

Interpretation. Petrifilm plates can be used in a variety of ways:

• Petrifilm plates can be hydrated with a bacterial culture, or a dilution of a
culture, for counting the viable organisms present. See Method A.

• Petrifilm plates can be hydrated first with water or buffer, then inoculated
by swabbing, streaking, or touching to surfaces. See Method B.

• Antibiotics can be added to the hydration fluid to select for resistant
organisms in Method A or B.

• Cells can be removed from colonies growing on Petrifilm plates and used
to inoculate additional cultures or for staining.

• Experimental results on Petrifilm plates can be saved for future reference
by scanning the plates on a standard computer-linked scanner. Do not
open the plates for scanning.

Petrifilm plates were developed for use in the food and beverage industry.
They have been certified for official analyses in many countries. For more
information about these applications, see the 3M page on the World Wide
Web at www.3m.com.

©2000 Carolina Biological Supply Company Printed in USA

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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. Disinfect the work area
by wiping thoroughly with alcohol or other disinfectant before and after use.
Used Petrifilm plates may contain viable organisms. Do not open the plates
unnecessarily. The procedures in this instruction booklet should be used for
educational purposes only.

Method A. Inoculation with liquid sample

Inoculate and spread each Petrifilm plate before going on to the next plate.

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. 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.

Figure 3

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