Acid fast staining Q

[lordman]

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What makes Mycobacterium stains with ZN stain?
1-cord factor
2-surface lipids

I know that it stains because of lipids. However, choices are confusing! cord factor, although just a virulent factor and not the direct cause of staining, it has two mycolic acids, so lipids!

 

[Myxedema]

Just because something has a lipid component doesn't mean it has a big role in the staining of the bacterium.

 

[stronghold]

Seems a hard question!

 

[notbobtrustme]

errr, mycolic acids are separate from lipids. They are unique, large, hydrophobic acids that tether themselves to proteins/lipids/cord factor, but aren't lipids per-se. They are more like wax than anything else.

Anyways, by definition, ZN stains mycolic acid and cord factor is composed of mycolic acid, so there's yer answer.

 

[Transposony]

What makes Mycobacterium stains with ZN stain?
1-cord factor
2-surface lipids

I know that it stains because of lipids. However, choices are confusing! cord factor, although just a virulent factor and not the direct cause of staining, it has two mycolic acids, so lipids!

The key word here is mycolic acid, which is responsible for the acid fast-ness and is the common denominator among acid fast organisms like Mycobacteria, Nocardia, Corneybacterium etc.

It is the high lipid due to mycolic acids and long chain fatty acids, which causes them to bind and retain the complex basic dye carbol-fuchsin.

Cord factor is the virulence factor for mycobacterium due to the fact that it contains mycolic acid. Also, the surface lipid of mycobacteria has free mycolic acid along with other glycolipids like lipoarabinomannan. This means that cord factor is a part of cell wall. But since surface lipid is too non specific I'll go for cord factor since it for sure contains mycolic acid with bind with carbol-fuchsin.