This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
Acid fastness of tubercle bacilli is 
Select and explain. 
A. Presence of mycolic acid, B. Integrity of cell wall, C. Both of the above, D. None of the above
A: Presence of mycolic acid
Answer: A: Presence of mycolic acid 
Explanation: Acid fastness - ability to resist decolorisation TB bacilli is 20 % acid fast This propey is due to presence of mycolic acid it has nothing to do with integrity of cell wall