Capsule Staining by Manewal's staining method.

Hey lovelies..
Today the topic of discussion is capsule and their staining.
So, what is a capsule?

It is mostly polysaccharide layer around the cell, but may also contain polyamines and polyalchols,together also often termed as glycocalyx. They can be rigid avoiding any dyes or antibiotics, or they can be slime which can be easily deformed.
Capsules increases virulence of micro-organisms preventing them from phagocytosis, prevents dehydration and provides attachment to the host cells.

So, how can it be observed??
By a simple and preferred microscopic staining technique using Manewal's method.
Manewal's staining technique uses tow stains:

1. Congo red as negative stain.
2. Manewal's stain (Mixture of acetic acid and acid fuchsin).

Now congo red is a pH indicator dye which will turn blue if the surrounding pH lowers at or below 3. Hence the cells are first stained with congo red which colors the entire background and the cells in red color. When Manewal's stain is added after congo red, the acetic acid in the stain lowers the pH of congo red causing it to turn blue. Acid fuchsin present in the stain colors the cells bright red. The capsule remain colorless and is observed as a space between the cell and blue background.

When observed under light microscope you will see bright red cells surrounded by a circular colorless space (which is the capsule) and the background as blue. If the capsule is absent you will observe red cells present in the entire blue background.

Protocol:
A very simple method that we followed was:

1. Taking a drop of congo red to one end of the slide.
2. Pick up a small isolated colony and mix with stain.
3. Now take an another smooth edged slide, and drag the drop to the other end of the slide forming a film.
4. Allow it to dry for 2-3 minutes.
5. Directly add Manewal's stain and after 4-5 minutes drain the excess stain.
6. Allow the slide to dry and observe under oil immersion

Lots of Love
-Staph