BISC209: Preparing a bacterial smear slide

Preparing a bacterial smear slide

Preparing a bacterial smear slide is useful for microscopic examination of dead bacterial cells.
1. Place a very small loopful of tap or deionized water on the slide (you can use the deionized water bottle on your bench-remove the cover and dip your loop in – sterility is not required for this step).
Note: If the bacterial smear is being made from a broth, simply place a loop or two of the broth culture on the slide and spread, do not use additional water.
2. Flame the loop, cool and touch it to the colony or slant growth and place the now contaminated loop into the drop. Use large circular motions to spread the drop to about the size of a quarter over the slide.
3. Reflame the loop.
4. Be sure all the water on the slide has evaporated before proceeding to heat fixation.
5. Heat fix (kills and attaches organisms to slide) by rapidly passing the slide (smear side up) through a flame 3 times. Use a slide holder and avoid contact with hot glass.

With practice it is more efficient to put multiple samples on one slide. Just be careful to apply the solutions so they cover all the smears evenly and for the same amount of time. Label the slide in the ground glass section or far left of the slide and be aware that the ingredients in the Gram Stain can remove your labels. By convention the labels (top to bottom) match the smears (right to left).
An example of a multiple smear labeled slide: