Pulmonary Tuberculosis (TB) is an infectious disease that largely affects the lungs. It can be generally transmitted to other parts of the body such as in the lymph nodes, bones, kidneys and meanings which is referred to as extra-pulmonary tuberculosis. The principal infectious agent is Mycobacterium tuberculosis, is an acid fast aerobic rod shaped bacteria that grow insidiously and is highly sensitive to heat and ultraviolet light. Other similar causative agents such as Mycobacterium avium and Mycobacterium bovis are likewise associated with the development of TB infections.
Pulmonary Tuberculosis is global public health problem with mortality and morbidity rates still continuing to rise especially in developing countries. Mycobacterium tuberculosis infects as estimated one third of the world’s population and is considered to be the leading cause of death of communicable and infectious disease in the world according to the World Health Organization. TB is closely associated with poverty, overcrowding, malnutrition, inadequate health care, poor sanitation practices and substandard housing.
Transmission and risk factors of Pulmonary Tuberculosis
Pulmonary tuberculosis spreads from person to person primarily by airborne transmission. An infected individual release droplet nuclei (particles 1 to 5 µm in diameter) through coughing, sneezing, talking and laughing. Larger droplets settle while much smaller droplets remain suspended in the air which can be inhaled by unsuspecting and highly susceptible individuals. Risk factors for TB include:
- Immunocompromised individuals such as those with HIV infection, cancer patients undergoing chemotherapy.
- Close contact with someone who has active TB, inhalation of airborne nuclei from an infected person.
- Any person without adequate health care including the homeless, impoverish, emaciated/malnourished individuals, the very young and very old.
- Institutionalized individuals under long-term care such as is prison facilities and mental health institutions.
- People living in overcrowded and substandard housing with poor sanitation practices.
Pathophysiology of Pulmonary Tuberculosis
Pulmonary Tuberculosis begins when a susceptible individual inhales the causative agent causing TB and becomes infected. The bacteria are transmitted through the airway to the alveoli where the microorganisms are deposited and begin to multiply at an exponential rate. The bacilli are also transported via the blood stream and the lymphatic system to other organ systems which is responsible for extra-pulmonary TB infections. After the initial exposure and infection of TB, active disease may develop when the immune response becomes compromised due to an underlying disease condition or low immunity status of an individual. Active disease may also occur with the infection and activation of dormant Mycobacterium tuberculosis bacteria.
Clinical manifestations of Pulmonary tuberculosis
The manifestations of the signs and symptoms of pulmonary tuberculosis are
usually slow and insidious. Most individuals with active TB infection of the lungs have low-grade fever, night sweats, weight loss and fatigue. The incessant coughing may or may not be productive, coughing out of blood is present during the advance stages of the disease. Both the systemic and pulmonary symptoms are chronic and may have been present for several weeks and even months. Finally, elderly patients commonly are presented with much less pronounced symptoms than younger patients suffering from pulmonary tuberculosis and patients with HIV-AIDS, extra-pulmonary TB infection is more prevalent than pulmonary tuberculosis.