Carolina 3M Petrifilm Yeast & Molds Count Plates - Manual (Page 3)

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.