The preparation of a smear is required for many laboratory procedures, including the Gram-stain. The purpose of making a smear is to fix the bacteria onto the slide and to prevent the sample from being lost during a staining procedure. A smear can be prepared from a solid or broth medium. Below are some guidelines for preparing a smear for a Gram-stain.
1. Place one needle of solid bacterial growth or two loops
of liquid bacterial growth in the center of a clean slide.
2. If working from a solid medium, add one drop (and only one drop)
of water to your specimen with a water bottle. If using a broth
medium, do not add the water.
3. Now, with your inoculating loop, mix the specimen with the water
completely and spread the mixture out to cover about half of the
total slide area.
4. Place the slide on a slide warmer and wait for it to dry. The smear is now ready for the staining procedure.