In this module, you have learned that...

• TB is an infectious disease caused by the Mycobacterium tuberculosis (M. tuberculosis).
• People who have pulmonary TB (PTB) are infectious and can transmit TB to others.
• Primary infection occurs on initial exposure to M. tuberculosis.
• Since inhaled droplet nuclei (containing M. tuberculosis) are so small, they can escape the mucociliary defenses of the bronchi and lodge in the terminal alveoli of the lungs.
• Infection begins when the bacilli start replicating in the lungs, forming the pneumonic focus.
• Post-primary TB may develop several years after the primary infection as a result of reactivation of a latent TB focus.
• Drug resistance can be primary or acquired – but is often the result of monotherapy