Rosh Internal Medicine Boost Practice Exam

For a medical student showing a 13 mm induration in a Mantoux tuberculin skin test, what monotherapy is appropriate?

1. Ethambutol

2. Isoniazid

3. Pyrazinamide

4. Streptomycin

The correct answer is: Isoniazid

In the scenario of a 13 mm induration observed in a Mantoux tuberculin skin test, the appropriate monotherapy is Isoniazid. A 13 mm induration typically indicates a positive test for tuberculosis, especially in individuals who have certain risk factors or are in higher risk categories, such as healthcare workers or the immunocompromised. Isoniazid is the first-line treatment for latent tuberculosis infection (LTBI) and is effective in preventing the progression to active TB disease. It works by inhibiting mycolic acid synthesis in the bacterial cell wall, which is crucial for the growth and replication of Mycobacterium tuberculosis. This makes it a primary choice in the management of LTBI, particularly in cases where the individual is at significant risk for developing active disease. Ethambutol, Pyrazinamide, and Streptomycin are also used in the treatment of active tuberculosis but are not first-line agents for LTBI. Ethambutol is primarily used in combination therapy for active TB due to its efficacy against drug-resistant strains. Pyrazinamide is effective in the intensive phase of treatment for active TB but is not typically used for latent infections. Streptomycin is guided mainly in resistant cases