Question

1)Describe the progression of a DIFFERENT bacterial, fungal OR protozoan microbial pathogen (causes disease) from acuteinfection to acuteinflammation to acutenecrosis to chronicinfection and chronicinflammation and chronicnecrosis.

(Virus assigned for this question is tuberculosis)

Answer 1

Tuberculosis is caused by Mycobacterium tuberculosis. The progression from acute to chronic stages of tuberculosis are as follows-

1. This organism is spread easily and pulmonary infection usually results from inhalation of small droplets of respiratory secretions that contains a few bacilli. This inhaled bacilli are ingested by alveolar macrophages and are able to survive and can be multiplied intracellularly by inhibiting phagolysosome formation. The infected macrophages lyse eventually as a result large number of bacilli are released. A cell mediated response CD4+ T cells is responsible for much of the tissue damage in the disease.

2. In this pattern of pulmonary tuberculosis , CD4+ T cells are activated within 2-6 weeks after infection, inducing the infiltration of large numbers of activated macrophages. These cells walls off the organism inside a granulomatous lesion called a tubercle.

3. From this phase chronic progression starts. This progression may occur years after the primary infection. In this clinical pattern accumulation of large concentrations of mycobacterial antigens within tubercles leads to extensive and continual chronic CD4+ T cell activation and ensuing macrophage activation. The resulting high concentrations of lytic enzymes cause the necrotic caseous lesions to liquefy, creating a rich medium that allows the tubercle bacilli to proliferate extracellularly. Eventually with time the lesions rupture and the bacilli disseminate in the lung and are spread through the blood and lymphatic vessels to the pleural cavity, bone, urogenital system, meninges, peritoneum or skin.