Question

A culture of Mycobacterium leprae was subjected to alkaline ethanol extraction before acid-fast staining. The color of the culture following staining will be
A. Red
B. Green
C. Yellow
D. Blue.

Answer 1

Hint:- The bacteria which possess certain features that resist the bacteria from taking stain or decolorization acid medium. These bacteria are known as acid-fast bacteria or AFB. The process of acid fastness is not only applied to the bacteria but also attributes to other structures of an organism. This structure involves the sperm head, Sarcocystis, cysts of Hydatid, etc. Example: Mycobacterium sp.

Complete step-by-step solution:- Acid fast bacteria causes mainly mycobacterial infection or Tuberculosis. The two most common tests which are done to identify the acid-fast bacteria are Ziehl- Neelsen stain and Kinyoun method.
The acid-fast testing method involves:
- The first sample is collected from the patient.
- The smear is prepared.
- Heat fixation of the smear is done. Heat fixation involves 60C temperature. After providing the heat the smear is allowed to sit for 5min.
- Then fuchsin stain is applied.
- Then Washing of stains is done by the water.
- 3% acid alcohol solution is applied then for 2-5 min.
- Then the smear is washed again with water.
- .5% methylene blue is then added to the smear and allowed to sit for 1-2 min.
- Then again washing, air drying is done.
- The prepared sample is then checked under the microscope.

Note:- The group of bacteria which does not show a positive result in the acid-fast technique is called nonacid fast bacteria. The nonacid fast bacteria stains in blue color. The acid-fast bacterial wall contains a long fatty acid called mycolic acid. Mycolic acid is responsible for the positive result shown by the acid-fast bacteria during the acid-fast process. Mycolic acid is found in the cell wall of Tuberculosis.