Answer
The waxy, fatty chemicals in their cell walls act like a waterproof shield that blocks stains and antibiotics.
Work Step by Step
Bacteria like those that cause TB and leprosy have special cell walls that contain a lot of waxy, fatty (lipid) materials, mainly a substance called mycolic acid.
Because of this:
1. They are hard to stain
The waxy layer acts like a waterproof coat.
Normal stains cannot pass through easily.
That is why you must use steam heat, which softens the wax and helps the stain enter the cell.
2. They resist many antibiotics
The thick, waxy layer also works like a strong shield.
Many antibiotics cannot pass through this fatty layer.
This makes it difficult for the drug to reach inside the bacteria to kill it.
Chemical explanation:
The cell wall contains long-chain fatty acids (mycolic acids).
These fatty acids are hydrophobic (water-hating).
Because they repel water, they block water-based stains and antibiotics, which makes the bacteria:
Hard to stain
Hard to kill
