TB is a communicable disease caused by Mycobacterium tuberculosis , or the tubercle bacillus. If another person inhales air containing these droplet nuclei, transmission may occur.
Some bacilli reach the alveoli, where they are ingested by macrophages.
Infection begins with the multiplication of tubercle bacilli within these alveolar macrophages. Although the majority of TB cases are pulmonary, TB can occur in almost any anatomical site or as disseminated disease. In the United States, the vast majority of TB cases are caused by Mycobacterium tuberculosis , sometimes referred to as the tubercle bacillus. Mycobacteria other than those comprising the M. tuberculosis complex are called nontuberculous mycobacteria. What the Clinician Should Know 4th.