To identify the presence of mycobacterium tuberculosis, which test should be ordered?

The acid-fast stain is the appropriate test to identify the presence of Mycobacterium tuberculosis due to its unique cell wall structure that incorporates mycolic acids, making it resistant to conventional staining techniques. In this test, a specimen is treated with specific dyes, such as carbol fuchsin, followed by a decolorization process and a counterstain. The acid-fast bacilli retain the original dye, appearing bright red under a microscope, while non-acid-fast bacteria take on the counterstain color, which typically appears blue. This characteristic makes the acid-fast stain a reliable and rapid method for diagnosing tuberculosis.

Culturing tests can also confirm the presence of M. tuberculosis but typically take weeks to yield results due to the slow-growing nature of the bacteria. X-rays are useful for assessing lung pathology associated with tuberculosis but do not directly identify the organism. Blood tests for tuberculosis can evaluate immune responses but are not definitive for identifying the bacteria itself. Each of these methods serves a role in the broader diagnostic process, but the acid-fast stain directly identifies the bacteria efficiently in clinical settings.