CARBOL FUCHSIN TENSOACTIVE, 1000 mL

PRINCIPLE

Ziehl–Neelsen staining is used to diff erentiate acid-fast microorganisms. These microorganisms have a special lipid cell wall, which contains mycolic acid, amongst other substances. This enables the wall to resist destaining with acid-alcohol after staining with basic dyes such as fuchsine. The cell wall appears a reddish-pink colour, while the remainder of the microorganisms are stained with the counterstain, normally Methylene Blue. Classic staining requires heat in order for the stain to penetrate the bacterial wall. It appears that intact cells are required in order for the acid-fast property to be demonstrated. It is assumed that permeability through intact membranes may be an important component of the mechanism involved in the phenomenon of resistance to destaining by the acid-alcohol solution indicated above. Although the mechanism of diff erentiation is not fully established, the method is fully accepted as a procedure for early diagnosis, as well as to provide information on the number of bacilli present in the sample. Acid-fast microorganisms are basically mycobacteria, although there are other microorganisms which also present this characteristic, such as the genus Nocardia and some parasites, such as Cryptosporidium.

DIAGNOSTIC USE

Stains for Ziehl–Neelsen staining are used to perform staining of cultures or samples which are suspected of containing mycobacteria, for early diagnosis of mycobacterial infection and its characterisation.