Which specimen is routinely decontaminated when trying to recover Mycobacterium species?

• A. Sputum
• B. Pleural fluid
• C. Lung biopsy
• D. Cerebrospinal fluid

Answer: (A)

Processing to recover Mycobacterium often starts with removing other bacteria that can overgrow the culture. Sputum is routinely decontaminated because it comes from the respiratory tract and is filled with normal oral flora. Using a chemical decontaminant (such as NaOH with NALC) liquefies mucus and kills many bacteria and fungi, while Mycobacterium species remain viable long enough to be concentrated and cultured. In contrast, pleural fluid, cerebrospinal fluid, and lung tissue are normally sterile or have much lower contamination, so they are not routinely subjected to the same decontamination process, and aggressive alkali treatment could harm the organisms being sought. Therefore, sputum is the specimen commonly decontaminated.