What is the generally recommended digestion and decontamination method for processing clinical specimens for recovery of Mycobacterium tuberculosis?

• A. 6% NaOH
• B. HCl
• C. NALC-NaOH
• D. Trisodium phosphate

Answer: (C)

Processing specimens for Mycobacterium tuberculosis relies on liquefying mucus and removing contaminating organisms while keeping the tubercle bacillus viable. The standard approach uses N-acetyl-L-cysteine (NALC) as a mucolytic to break down sputum and Sodium hydroxide (NaOH) as a decontaminant. This NALC-NaOH combination, followed by neutralization and concentration of the bacilli via centrifugation, preserves M. tuberculosis better than stronger acids or bases alone and reduces overgrowth by contaminants. Higher concentrations of NaOH alone can kill or harm the mycobacteria, lowering yield, which is why that option isn’t preferred. HCl or trisodium phosphate aren’t the typical digestion/decontamination methods used for routine recovery of M. tuberculosis. So, the recommended method is the NALC-NaOH approach.