Which of the following is a major component of TB drug therapy?

Isoniazid is a major component of tuberculosis (TB) drug therapy because it is one of the first-line agents used in the treatment of both drug-sensitive and, in some cases, drug-resistant TB. Isoniazid works by inhibiting the synthesis of mycolic acids, which are essential components of the bacterial cell wall in Mycobacterium tuberculosis. This inhibitory action is crucial for effectively reducing the bacterial load in an infected patient.

The significance of isoniazid in TB therapy is underscored by its effectiveness when used in combination with other first-line drugs, such as rifampicin, pyrazinamide, and ethambutol, which together form a comprehensive treatment regimen. This multi-drug approach helps prevent the development of resistance and improves treatment outcomes.

Other options listed, such as amphotericin B, posaconazole, and azole antifungals, are not used in the treatment of TB. Amphotericin B primarily targets fungal infections, while posaconazole and azole antifungals are also antifungal agents, making them irrelevant in the context of treating a bacterial infection like TB.