Introductory scenario A patient visits the local free clinic with complaints of

Question

Introductory scenario A patient visits the local free clinic with complaints of night sweats and excessive coughing. He is fatigued and has a fever. When giving his patient history, he reports that he recently returned from a mission trip in Africa. Clinic staff members are concerned that the patient may have tuberculosis (TB) and send the patient to the emergency department (ED). At the hospital, the ED employees take droplet precautions with the patient and call the laboratory for consultation. The physician assistant (PA) in the ED talks to the microbiologist about TB testing. The microbiologist explains that the type of bacteria that causes TB, Mycobacterium tuberculosis, is very slow growing. Growth through culture is not usually seen for 2 to 4 weeks, and susceptibility testing typically takes 2 to 4 weeks after that. Continue to questions Chapter 12 Molecular Diagnostic Techniques

Explanation / Answer

1) As the culturing of Mycobacterium tuberculosis takes too much time, the microbiologist would recommend amplification testing to detect the bacterium through the presence of its DNA(b). It is the fastest method for the diagnosis of tuberculosis, even if the load of bacterium is low. The Gram staining is not recommended for the identification of this bacterium, due to the presence of mycolic acid in its cellwall which cannot absorb the stain.

2) The amplification technique used for the rapid diagnosis of Mycobacterium tuberculosis is the Polymerase chain reaction or PCR (A). This is the fastest and sensitive method for the diagnosis of tuberculosis, by the identification DNA of causative organism.

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