Which test is commonly used to identify Mycobacterium tuberculosis?

The acid-fast bacillus (AFB) smear is a commonly used test for identifying Mycobacterium tuberculosis due to the unique characteristics of this bacterium. Mycobacterium tuberculosis has a waxy cell wall, primarily composed of mycolic acids, which gives it the property of acid-fastness. During an AFB smear, a sputum sample is stained using special dyes (such as the Ziehl-Neelsen stain), followed by an acid-alcohol wash. If the mycobacteria retain the dye and appear red under a microscope, it indicates the presence of acid-fast bacilli, confirming the potential presence of Mycobacterium tuberculosis.

While other tests like PCR and culture tests are also valuable for diagnosing tuberculosis, the AFB smear is particularly significant for its rapid preliminary results. ELISA tests are not typically employed for the direct detection of Mycobacterium tuberculosis and are rather used for serological testing in other contexts. Therefore, the AFB smear is a cornerstone in the laboratory diagnosis of tuberculosis due to its specificity, speed, and effectiveness in highlighting the presence of the bacterium.