A patient with multidrug-resistant TB would likely be treated with which drug class?

• A. A fluoroquinolone
• B. Isoniazid
• C. Rifampin
• D. Ethambutol

Answer: (A)

Multidrug-resistant TB arises when the TB bacteria are resistant to at least isoniazid and rifampin, the two most potent first-line drugs. Because of this, treatment shifts to second-line agents, with fluoroquinolones coming to the forefront. Fluoroquinolones such as levofloxacin or moxifloxacin have strong bactericidal activity against Mycobacterium tuberculosis and penetrate well into tissues and inside cells, making them highly effective against resistant strains when used as part of a coordinated regimen. The other options are first-line drugs that MDR-TB strains are resistant to, or are less central to MDR-TB therapy, so they’re not the primary class used in this situation.