ence monitoring the number of stainable organisms in

the sputum during treatment can provide an early and

objective measure of response.

It should be noted that in patients receiving

antimycobacterial therapy not all stainable organisms are

viable. Should the number of organism fail to decrease

after therapy is started, the possibility of drug resistance

must be considered. Additional cultures should be taken

and drug susceptibility studies obtained.

Two types of acid-fast stains are frequently used:

1. Carbol fuchsin based stains;

2. Fluorochrome based stains.

The carbol fuchsin stains, so called because of the

Reagent formed by mixing of the stain basic fuchsin with

the disinfectant phenol (carbolic acid). Carbolfuchsin

stained mycobacteria appear bright red/pinkish against a

bluish background.

Two procedures using carbol fuchsin based stains are in

common use:

a. Three component Ziehl-Neelsen, or “hot stain”, and

b. Three component Kinyoun or “cold stain”.

The Kinyoun stain is a modification of the classical

Ziehl-Neelsen “hot stain”. The classical Ziehl-Neelsen

“hot stain” requires application of heat to the fixed smears

flushed with the stains during staining process, whereas

the Kinyoun stain does not require the application of heat

and is less tedious to perform and standardize.

Recent advances in staining techniques have been

reported where the cold Kinyoun stain has been further

modified to accommodate the decolorizer within the

counter stain. The novel two component two step stain is

time, labor and cost saving, more user friendly and easy to

standardize. It also has good correlation with the classical

Ziehl-Neelsen “hot stain” and AFB cultures.

Contd...

Microbiology and Bacteriology 851

RAPID TWO STEP COLD AFB STAIN

(Courtesy: Tulip Group of Companies)