In processing sputum samples to isolate Mycobacteria, which sequence is correct?

In processing sputum samples to isolate Mycobacteria, which sequence is correct?

• A. Digestion > decontamination > centrifugation
• B. Digestion > decontamination > neutralization > centrifugation
• C. Decontamination > digestion > centrifugation > neutralization
• D. Centrifugation > digestion > decontamination > neutralization

Answer: (B)

Processing sputum for Mycobacteria relies on a sequence that first liquefies the mucus, then reduces competing flora, then restores a neutral pH, and finally concentrates the target organisms. Liquefying the sample with a mucolytic (digestion) frees the organisms from the thick mucus and improves contact with the decontaminant. Decontamination with an alkali kills many non-mycobacterial bacteria that could overgrow cultures. After that, neutralization brings the pH back to neutral so the mycobacteria remain viable and are less harmed by the alkali. Finally, centrifugation concentrates the organisms into a pellet for inoculation or further processing. If digestion happens after decontamination or centrifugation occurs before neutralization, the effectiveness of decontamination is reduced, and residual alkaline conditions can harm the Mycobacteria or reduce yield.

Processing sputum for Mycobacteria relies on a sequence that first liquefies the mucus, then reduces competing flora, then restores a neutral pH, and finally concentrates the target organisms. Liquefying the sample with a mucolytic (digestion) frees the organisms from the thick mucus and improves contact with the decontaminant. Decontamination with an alkali kills many non-mycobacterial bacteria that could overgrow cultures. After that, neutralization brings the pH back to neutral so the mycobacteria remain viable and are less harmed by the alkali. Finally, centrifugation concentrates the organisms into a pellet for inoculation or further processing. If digestion happens after decontamination or centrifugation occurs before neutralization, the effectiveness of decontamination is reduced, and residual alkaline conditions can harm the Mycobacteria or reduce yield.