Tuberculosis (TB)


Tuberculosis (TB)

Definition of Tuberculosis (TB)

Tuberculosis is a chronic granulomatous disease caused by bacteria belonging to the Mycobacterium tuberculosis complex.

  • The disease usually affects the lungs, although in up 1/3rd of cases other organs are involved.
  • Transmission usually takes place through the airborne spread of droplet nuclei produced by patients with infectious pulmonary tuberculosis.
  • The causative organisation (M. tuberculosis (Tubercle bacillus or Koch’s bacillus)] is a strick aerobe (0.5μm by 3μm) and thrives best in tissues with high oxygen tension such as in the apex of the lung.

Etiology (causes) of Tuberculosis (TB)

  1. Unpasteurized milk.
  2. Transmitted from a patient with infectious pulmonary tuberculosis by cough, sneeze, speaking.
  3. Through skin and placenta of infected person.

Types of Tuberculosis (TB)

Tuberculosis is classified as pulmonary or extra pulmonary. Before the recognition of HIV infection, more than 80% of all cases of tuberculosis were limited to the lungs. However, up to 2/3rd of HIV infected patients with tuberculosis may have both pulmonary and extra-pulmonary disease or extra-pulmonary alone.

Pulmonary Tuberculosis

It is categorized as primary and post primary (secondary)

  1. Primary Tuberculosis – It is seen in the person who has not infected previously. It is result of initial infection with tubercle bacilli. The organism enters the body through the lungs. Within an hour of reaching the lungs, the tubercle bacilli reach the draining lymph nodes at the hilum of the lungs and few organisms enter the systemic circulation (I.e, blood stream)
    Features – 
    1. Increased resistance is seen.
    2. T cells (cellular immunity) prevent the spread of disease and the organisms remain inactive in the host.
    3. Reactivation of tubercle bacilli leads to progressive primary tuberculosis or Miliary tuberculosis (hematogenous spread of tubercle bacilli the lesions formed are yellowish granulomas 1-2 mm in diamter that resemble millets seeds. Hence, the name Miliary).
  2. Secondary Tuberculosis (post Primary) – It is seen in persons who have already infected with primary lesions. It affects the apex of the lungs and other sites like tonsils, pharynx, larynx, small intestine and skin.
    Features –
    1. Caseous necrosis rapture of blood vessels, thereby spreading the mycobacteria throughout the body.
    2. Infection of the airway tract by mycobacteria.

Extra-pulmonary Disease

It is seen more commonly today than in past. In order of frequency the extra-pulmonary sites most commonly involved in tuberculosis are the lymph nodes, plerua, bones, joints, meninges, peritoneum and pericardium. However, virtually all organ systems may be affected. As a result of hematogenous determination in HIV infected individuals.

Tuberculosis details

Pathophysiology of Tuberculosis (TB)

Tuberculosis is an infectious disease which occurs when a droplet nuclei containing tubercle bacilli is inhaled.
arrowDroplet nuclei reach the terminal bronchioles and alveoli of the lungs and prevents the activation of defense mechanisms in the upper airways.
arrowAlveolar macrophages inject the bacilli but fail to destroy them.
arrowBacilli multiply within the macrophages.
arrowAs the Bacilli profliferate, macrophage present the bacilli as antigen to T-lymphocytes.
arrowThis increase the concentrate of degrading enzymes in macrophage and improve the ability to destroy the bacilli.
arrow[ CASE – 1 ]
When the pathogens inhaled are low and the host has an intact immune system, the destruction and control of bacilli results in formation of grey-white granulomatous lesion in lung called Ghon’s focus (Primary lesion), it contain bacilli, macrophages, immune cells.
arrow[ CASE – 2 ]
If pathogens inhaled are high and the host has compromised immune system.
arrowBacilli causes Ghon’s focus to undergo caseous (pasty, yellow and cheese like) necrosis.
arrowBacilli present in the Ghon’s focus drain along with lymph channels and reach the lymph nodes of affected lung.
arrowFrom caseous granulomas with Ghon’s focus, which is together called as Ghon’s complex (undergo healing)
arrowIf body’s defense mechanism fail, the primary infection turn into secondary tuberculosis.


Tuberculosis chest pain

Signs and Symptoms of Tuberculosis (TB)

A patient with active tuberculosis presents the following clinical manifestations:

  1. Fatigue, fever, night sweats and loss of weight.
  2. Cough which is initially non-productive but is accompanied by purulent sputum in the later stages. The production of sputum is triggered by inflammation and tissue necrosis.
  3. Patient, though rarely, may cough up blood in the sputum (haemoptysis).
  4. Chest pain and hoarseness of the voice.

Risk factors of Tuberculosis (TB)

  1. Infection with HIV, the virus that causes aids and weakens the immune system.
  2. Diabetes mellitus.
  3. Low body weight
  4. Head and neck cancer, leukemia/hodykin’s disease.

Complications of Tuberculosis (TB)

If left untreated, tuberculosis can be fatal. Although it mostly affects the lungs, it can also spread through the blood, causing complications, such as –

  • Meningitis : Swelling of the membranes that cover the brain.
  • Spinal pain.
  • Joint damage.
  • Damage to the liver or kidneys.
  • Heart disorders : this is more rare.

Prevention of tuberculosis (TB)

  1. Tuberculosis vaccination (BCG injections).
  2. Pasteurized milk helps prevent borine.
  3. Usage of respirators and masks.
  4. Isoniazid preventive therapy.
  5. Antivetroviral therapy (HIV patients)

Treatment for Tuberculosis (TB)

Medications are cornerstone of tuberculosis treatment. But treating tuberculosis takes much longer than treating other types of bacterial infections.
For active tuberculosis, you must take antibiotics for at-least six to nine months. The exact drugs and length of treatment depend on your age, overall health, possible drug resistance and the infection’s location in the body.

Most common Tuberculosis drugs are

  1. Isoniazid : Any bacterial infection infested due to complications of Tuberculosis is treated using Isoniazid. Consumption of Isoniazid should be on empty stomach since, if any food is consumed before or after 1 hour period of consuming Isoniazid then it may interact with foods containing tyramine, which may cause heavy increase in blood pressure and may even cause dizziness. The dosage differs from person, depending on the weight, work load and their daily in-take of food. If you have any prescribed drugs under consumption then it may increase the risk on in-take. It’s better to consult your doctor and share the prescription and get the proper approval before starting, stopping or changing the dosage of medication either Isoniazid or any other.
  2. Rifampin
  3. Ethambutol
  4. Pyrazinamide

If you have drug-resistant tuberculosis, a combination of anitbiotics called fluoroquinolones and injectable medications, such as amikacin or capreomycin, which are generally used for 20 to 30 months.
Some drugs that can be used as add-on therapy includes:

  • Bedaquiline (Sirturo)
  • Linezolid (Zyvox)

Read about World tuberculosis day that is going to be celebrated on 24th March this year. Have a glance on it’s theme, which is “It’s time”. Understand why we must take a stand against Tuberculosis and start treating it as much as possible. World TB Day 2020 Theme (Tuberculosis)

Some more related diseases can be found below :
Ischemic Heart Disease –
Hypertension (High Blood Pressure) –
Jaundice –

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