In the decontamination and digestion procedure for the isolation of mycobacteria from sputum samples, what is the role of NALC?

• A. Bactericidal for normal biota
• B. Liquefies mucus
• C. Growth stimulant
• D. Neutralizes pH to prevent damage to mycobacteria

Answer: (D)

The main idea here is that NALC acts as a mucolytic agent in the sputum processing step. N-acetyl-L-cysteine breaks down the mucus, liquefying the sample so Mycobacterium tuberculosis and other mycobacteria are released from the thick, mucous matrix and can be concentrated for culture. The NaOH in the same procedure is the decontaminant that kills many of the normal respiratory bacteria, reducing overgrowth. After digestion and decontamination, the mixture is neutralized with an appropriate buffer to protect the mycobacteria from damage by the alkaline NaOH. So, the role of NALC is to liquefy mucus and release organisms, not to neutralize pH itself.