Pretomanid is used in combination regimens for highly drug-resistant TB. It is not used for latent TB infection, and it should not be used as monotherapy for MDR-TB because TB treatment relies on multiple drugs to prevent resistance and ensure effective killing of the bacteria. In practice, pretomanid is included with other drugs, most commonly bedaquiline and linezolid, as part of regimens for adults with MDR-TB or XDR-TB that have limited treatment options. This combination approach is what makes it the appropriate context among the choices.

Drugs are classified by their role in treatment: primary versus secondary. Primary drugs are the first-choice agents used in the initial, standard TB regimen because they have strong bactericidal activity, good tolerability, and work well together to prevent resistance. Secondary drugs come into play when the initial regimen fails or when the strain is resistant or the patient cannot tolerate the primary drugs; these options are used for retreatment or drug-resistant TB and often have more toxicity and a narrower evidence base. This framework keeps therapy effective and helps prevent the emergence of resistance by reserving the more potent or specialized drugs for when they’re really needed.

Longer therapy for MDR-TB is needed because the bacteria causing this form are resistant to the most potent first-line drugs, so the regimen cannot kill the infection as quickly or as completely. Treating MDR-TB relies on a combination of second-line drugs that have different targets, but these drugs are generally less potent and have slower bactericidal and sterilizing activity. To achieve a durable cure and prevent relapse, the course must be long enough to eradicate both actively growing bacilli and persisting dormant bacteria. Using multiple drugs in combination also helps prevent the bacteria from developing additional resistance, which is more likely if treatment is too short. While patient adherence matters, the overarching reason for the longer duration is the need to overcome resistance with a less potent drug mix and to ensure complete, lasting eradication.

Imaging provides a clear map of how widespread tuberculosis is and where it has spread beyond the lungs, which is essential for planning care. A chest X-ray is usually the first step and can reveal typical TB patterns such as upper-lobe infiltrates, cavitation, and signs of pleural effusion or other complications. CT adds detail when the chest X-ray isn’t enough, helping to identify mediastinal or hilar lymph node involvement and to detect extrapulmonary sites that might not show up on X-ray alone. This information guides practical decisions: where to obtain diagnostic samples to confirm TB, how to tailor treatment in complex or extrapulmonary cases, and how to anticipate potential complications. Imaging is also used to monitor how the disease responds to therapy by showing changes in lesion size or number, cavity resolution, or reduction of effusions. However, imaging alone cannot confirm TB; microbiological tests (like cultures or molecular tests) are still required for a definitive diagnosis. Also, radiographic improvement may lag behind actual bacteriologic clearance, so treatment decisions rely on microbiology and the clinical picture in addition to imaging.

Bedaquiline has safety signals you must actively watch for: it can prolong the QT interval on the ECG and can cause liver injury. Because of the risk of dangerous arrhythmias, an ECG should be done at baseline and then periodically during treatment to monitor QTc. Liver function tests are also important, with baseline values and repeats during therapy to catch potential hepatotoxicity early. Visual testing won’t reveal cardiac repolarization changes or liver injury, and focusing only on renal function misses the main risks. So, monitoring these two areas—ECG QTc and liver function tests—is essential, rather than assuming no monitoring is needed.