Which specimen is routinely decontaminated when trying to recover Mycobacterium spp.?

Which specimen is routinely decontaminated when trying to recover Mycobacterium spp.?

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

Answer: (D)

Sputum is routinely decontaminated because the respiratory tract carries abundant normal flora that can overgrow cultures. Mycobacteria grow slowly, so reducing competing bacteria with a decontamination step (such as NaOH or NALC-NaOH digestion) helps isolate and recover them more reliably. Other specimens like lung tissue biopsies, pleural fluid, or cerebrospinal fluid come from sterile or low-flora sites, so decontamination is not routinely used there; harsh decontamination could damage or kill the mycobacteria and reduce yield, so these samples are processed with methods that preserve viability instead.

Sputum is routinely decontaminated because the respiratory tract carries abundant normal flora that can overgrow cultures. Mycobacteria grow slowly, so reducing competing bacteria with a decontamination step (such as NaOH or NALC-NaOH digestion) helps isolate and recover them more reliably. Other specimens like lung tissue biopsies, pleural fluid, or cerebrospinal fluid come from sterile or low-flora sites, so decontamination is not routinely used there; harsh decontamination could damage or kill the mycobacteria and reduce yield, so these samples are processed with methods that preserve viability instead.