Preparing a Slide Smear

Preparing a Slide Smear

A. Place the culture onto the slide.

1. Flame your loop to sterilize the metal and first add a loopful of water to the slide.
Use this procedure if the culture is to be taken from a Petri dish or a slant culture tube. Only a small amount of water is required. Do not transfer a huge bubble of water but rather a small bit.

2. Flame your loop and allow the loop to cool. Touch the colony from the Petri dish or slant to get a small amount of the bacteria on the loop.
Note that only a very small amount of culture is needed; if you can see a chunk of the culture on an inoculation loop already indicates that too much is taken. Flame the loop and try again. Also, do not push the loop into the inside of the agar. That will disrupt the cultures.

(Note: If the culture is from a suspension/liquid culture, transfer a drop of suspended culture to be examined on a slide with an inoculation loop instead of

B. Spread the culture on the slide

1. Spread the culture with an inoculation loop.
Allow the culture to be spread to an even thin film over a circle approximately the size of a dime. Thus, a typical slide can simultaneously accommodate 2 to 3 small smears if more than one culture is to be examined.

2. Spread the water/culture mix sufficiently so that it can air-dry evenly and completely.
All of the rest of the procedure requires you to air-dry the culture and not let the culture stay wet or be heated with the flame until air-dried completely.

C. Fix the culture to the slide

1. Fix the culture through a gentle flame, by moving the slide quickly in a circular fashion.
Go in a circular fashion to avoid localized overheating. The applied heat helps the cell adhesion on the glass slide to make possible the subsequent rinsing of the smear with water without a significant loss of the culture.

Heat could be applied to facilitate drying the smear, however, this is not the point of flaming and if you have a lot of water on the slide that is not still present, spread it out with a loop before flaming. There should be little to no water present on the slide. Ring patterns can form if heating is not uniform, e.g. taking the slide in and out of the flame, this will mess up the stain and the smear must be restarted.

2. After the slide has cooled for about 1 minute proceed to the first step of the stain to be done

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