Question

How long does TB diagnosis take via culture in liquid/solid media?

1) 1-2 weeks
2) 2-4 weeks
3) 4-6 weeks
4) 6-8 weeks

Answer 1

TB diagnosis via culture takes 1-2 weeks in liquid media and 4-6 weeks in solid media due to the slow growth of M. tuberculosis. Colony morphology and molecular tests are used to confirm the presence of the bacterium.

Step-by-step explanation:

The diagnosis of tuberculosis (TB) via culture in liquid media can take 1-2 weeks, while a culture on solid media generally takes 4-6 weeks. This difference in time is because Mycobacterium tuberculosis (M. tuberculosis), the bacterium that causes TB, grows very slowly.

Upon direct microscopic examination using the Ziehl-Neelsen technique, acid-fast bacilli can be detected, but the culture needs more time for M. tuberculosis to grow into visible colonies. The Löwenstein-Jensen (LJ) agar is a common solid media used for TB cultures.

For a definitive diagnosis, characteristic colony morphology and molecular tests such as nucleic acid hybridization or direct nucleic acid amplification (NAA) testing can be employed once growth is observed. The DNA of the bacterium is also distinguished by its high G+C content, which is vital in confirming the species is M. tuberculosis.