Carolina 3M Petrifilm Yeast Molds Count Plates User Manual

82-4010

3M™ Petrifilm™

Yeast and Mold Count

Plates

Instruction Manual

CAROLINA

®

Teamed with Teachers

Description

The 3M™ Petrifilm™ Yeast and Mold Count (YM) Plate is a ready-made
culture medium system that contains nutrients supplemented with
antibiotics, 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. Petrifilm YM plates can be used
in place of standard fungal nutrient media such as Potato Dextrose Agar in
many applications, as described below:

• Petrifilm plates can be hydrated with a 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.

• 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 converted into electronic files
by scanning the plates on a standard computer-linked scanner. Do not open
plates to scan them.

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.

Storage

Refrigerate unopened packages at ≤ 8ºC (≤ 46ºF). Use before expiration date
on package.

To seal an opened package, fold the end over and tape it shut (fig. 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.

Figure 1

©1999 Carolina Biological Supply Company Printed in USA

2

3

Safety

Petrifilm YM plates contain the antibiotics chloramphenicol and tetracycline
to prevent bacterial growth. The hydrated medium should not come into

contact with skin. Do not inoculate Petrifilm YM plates by touching them.

After use, Petrifilm YM plate will contain viable yeast and mold colonies.
Opening a used YM plate risks spreading spores. If allowed to sit for
several days, molds can grow out of the plates and spread spores. For
these reasons, it is recommended that Petrifilm YM plates be taped shut
after inoculation, and disposed of within a week of inoculation.

Use sterile technique when handling Petrifilm plates. Disinfect work area
before and after use, and wash hands before leaving the laboratory.

Directions for Use

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 buffer. If
antibiotics are to be added to the medium, add them to the inoculating
liquid at the working concentration.