Question

Frodo, a 32-year-old mineworker, has developed a persistent cough over the last two weeks accompanied with fever and night sweats. Her doctor is suspecting a tuberculosis (TB) infection.

a. List the detection methods that can be used to confirm TB diagnosis.

b. Name two drugs to be included in the first-line treatment regimen and discuss their mechanism of action in treating TB.

c. What is the purpose of the intensive and continuous phases of TB treatment?

d. While on first-line therapy, Frodo discovers that his contact lenses are starting to turn orange. Which drug is most likely responsible for this effect and why?

Due to his busy schedule, he has neglected to take his medication properly and has now developed a multidrug-resistant TB. The doctor has decided to add streptomycin to his treatment regimen.

e. Since starting his new treatment regimen, Frodo has been experiencing frequent bouts of vertigo. Discuss the most likely reason for this.

f. A few weeks later, Frodo develops an anaerobic bacterial infection in his GIT. He thinks that because he is already taking streptomycin, it should eradicate the infection. Discuss why this assumption is incorrect.

Answer 1

Answer:(a) There are two kinds of tests that are used to detect TB bacteria in the body:

1.The TB skin test (TST) and

2. TB blood tests.

Answer:(b) Isoniazid (INH), rifampin (RIF), ethambutol (EMB), and pyrazinamide (PZA) are considered first-line anti-TB drugs and form the core of standard treatment regimens.

Mechanism of action of INH:

Isoniazid is a prodrug that inhibits the formation of the mycobacterial cell wall. Isoniazid must be activated by KatG, a bacterial catalase-peroxidase enzyme in Mycobacterium tuberculosis. KatG catalyzes the formation of the isonicotinic acyl radical, which spontaneously couples with NADH to form the nicotinoyl-NAD adduct. This complex binds tightly to the enoyl-acyl carrier protein reductase InhA, thereby blocking the natural enoyl-AcpM substrate and the action of fatty acid synthase. This process inhibits the synthesis of mycolic acids, which are required components of the mycobacterial cell wall. A range of radicals are produced by KatG activation of isoniazid, including nitric oxide, which has also been shown to be important in the action of another antimycobacterial prodrug pretomanid.