Med. Mico. Lab Final_2.Preparation of Bacterial Smear

Why are thick or dense smears less likely to provide a good smear preparation for microscopic evaluation?

It will diminish the amount of light that can pass through making it difficult to visualize the morphology of single cells under the microscope.

Some times the stain can't penetrate all of the bacteria.

Why is it essential that smears be air-dried? Why can't they be gently heated over the flame to speed up the drying process?

1. Overheat will denature and rupture the cell wall. 2. excess water on the slides will boil during fixation destroying the overall shape of the bacteria

Why should you be careful not to overheat the smear during the heat-fixing process?

Overheating will distort the morphology through plasmolysis of the cell wall

*Why do you think the presence of grease or dirt on a glass slide will result in a poor smear preparations?

1. Bacteria will attach to the grease or dirt and wash away when staining. 2. It can also diminish the microscopic light making it hard to see the cells.