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Tuberculosis (TB) is a bacterial infection caused by Mycobacterium tuberculosis that primarily affects the lungs but can involve other organs. Diagnosis relies on clinical presentation, imaging studies, microbiological testing including acid-fast bacilli smears and cultures, and newer molecular diagnostic techniques like GeneXpert.
M. tuberculosis is transmitted through airborne droplets and establishes infection in alveolar macrophages, where it can remain dormant (latent TB) or progress to active disease. The bacteria's waxy cell wall containing mycolic acids makes it resistant to many antibiotics and allows it to survive within host cells, leading to granulomatous inflammation and tissue necrosis.
Treatment requires prolonged multi-drug therapy typically lasting 6-9 months with first-line agents (isoniazid, rifampin, ethambutol, pyrazinamide) to prevent resistance development. Drug resistance patterns, patient adherence, and potential drug interactions must be carefully considered when selecting treatment regimens, with directly observed therapy (DOT) recommended to ensure compliance and treatment success.
Key imaging focus: Apical cavitary lesions (reactivation), hilar lymphadenopathy (primary), miliary pattern