Tuberculosis

Tuberculosis
Etiology
TB properly refers only to disease caused by Mycobacterium tuberculosis (for which humans are the main reservoir). Similar disease occasionally results from the closely related mycobacteria, M. bovis, M. africanum, and M. microti—together known as the Mycobacterium tuberculosis complex.
TB results almost exclusively from inhalation of airborne particles (droplet nuclei) containing M. tuberculosis that formed by coughing, singing, and other forced respiratory maneuvers by people who have active pulmonary TB that include:
1- Smear +ve
2- pulmonary cavitary lesions are especially infectious because of the high number of bacteria contained within a lesion.
3- Laryngeal & endo-bronchial TB
Droplet nuclei (particles < 5 ? in diameter) containing tubercle bacilli may remain suspended in room air currents for several hours, increasing the chance of spread. However, once these droplets land on a surface, it is difficult to resuspendagain by sweeping the floor, shaking out bed linens. Contact with fomites (eg, contaminated surfaces, food, and personal respirators) do not appear to facilitate spread.