Page 43 - MNUmicrobiology practical 2025

General Microbiology & Immunology (PM 401) second level Semester 4 2024/2025

Bacterial smear preparation requirements

1. Clean and Grease or oil free slide

2. Bacterial broth culture

3. Inoculating loop.

4. Bunsen burner.
5. Slide holder.

6. Marker pen

Steps

1. Clean a plain microscope slide thoroughly using lens tissue.

2. Label a microscope slide with a marker pen to record the culture being used; this is

also a useful reminder of which side of the slide is being used.

3. Draw a circle on the center of the slide up to 2 cm length.

4. Flame a wire loop to ensure that no culture accidentally remains from a previous

operation.

5. Transfer 3-6 loopfuls of bacteria onto the center of the slide

Precaution
Do NOT make your smear suspensions too thick:

The dye will not penetrate well, and there will be far too many bacterial cells
to see individual shapes and arrangements

6. Gently spread the transferred loopfuls evenly over the marked area

Note
If you spread too aggressively, you will lose the bacterial

morphology
General Microbiology & Immunology (PM 401) Practical note Page 32