Tuberculosis was considered a pandemic back in the 18th century. This is a condition that affects the lungs majorly. The symptoms can appear in other parts of the body as well making it even more deadly. Today medical science has evolved especially in the area of treatment and diagnosis of this condition. The drugs that are used are fixed combination drugs. The government of India introduced the National tuberculosis elimination program to control the widespread. Free medications are provided on the prescription by the general physician. The common symptoms are fever, weight loss and loss of appetite. The general physician will advise CBNAAT and confirm the diagnosis. Don’t forget to concern your family physician to prevent further spread in your family.
What is tuberculosis?
Tuberculosis, caused by mycobacterium tuberculosis is one of the oldest diseases of mankind, and is a major cause of death worldwide. It usually affects the lungs, although other organs as well. The species causing tuberculosis are so closely related to each other by antigenic and molecular analysis that they are regarded by many scientists as variants of a single species. However, they can be distinguished from each other by certain properties.
Antigens of M.tuberculosis are mainly of two types:
Cell wall (insoluble) antigens : The cell wall consists of several distinct layers
Peptidoglycan layer: It maintains the shape and rigidity of the cell.
Arabinogalactan layer: It is a major structural component of the mycobacterium cell wall.
Mycolic acid layer: It is the principal constituents made up of long chain fatty acids attached to arabinogalactan. It confers very low permeability to the cell wall and is responsible for acid fastness and also reduces the entry of most of the antibodies.
Outermost layer: It consists of lipids, glycolipids and mycosides.
Proteins: They are found throughout the various layers.
Plasma membrane : This layer is present beneath the cell wall, into which various proteins, phosphatidylinositol mannosides, and lipoarabinomannan (LAM) are inserted. LAM is an important antigen, which facilitates the survival of tubercle bacilli within the macrophages. It is also used as a target antigen for the TB diagnosis.
Cytoplasmic(soluble) antigens: These include the antigen 5, antigen 6, and used in the diagnosis of tuberculosis.
How is tuberculosis transmitted
Mode transmission is mostly air or through the infected person. M.tuberculosis is mainly transmitted by inhalation of aerosols, generated while coughing, sneezing, or speaking of the infected patients. They are tiny dry droplet nuclei, which may remain suspended in the air for several hours and are easily inhaled. There may be as many as 3,000 infectious nuclei per cough. Consult your family physician or a general physician to follow the right measures.
Inoculation : Transmission of infection through direct skin contact with an infected person is uncommon.
Ingestion : Swallowing of sputum (in infants) or consumption of unpasteurized milk.
Risk factors
Risk factors favouring the transmission include:
Sputum positive patients ( sputum showing acid fast-bacilli in microscopy) transmit more efficiently than sputum negative patients.
Bacillary load : At least more than thousand bacillary load is required for an effective transmission. Adult patients with cavitary lesions in the lung have more bacillary load in sputum, therefore transmit more efficiently. Culture-negative pulmonary TB and extrapulmonary TB patients are essentially non infectious.
Overcrowding in poorly ventilated rooms. Following infection, not all, but only a minor proportion of people develop progressive disease. They usually have the following endogenous risk factors such as:
Low cell mediated immunity for example HIV infected people.
Other comorbid conditions such as post silicosis, post transplantation (renal, cardiac), jejunoileal bypass, gastrectomy, chronic renal failure/ hemodialysis, diabetes, IV drug abuse, smoking, etc.
Age is a factor as every stage of your life you have a different metabolism. Late adolescence and early adulthood periods are more prone. Elderly people are at increased risk due to waning immunity and underlying comorbidity.
Women are at higher risk of getting TB especially in the age group of 25-34 years of age, while at older age, men have a greater risk. Online consultation with your general physician can minimise the risk factors.
Types of tuberculosis
It is classified as pulmonary and extrapulmonary forms.
Pulmonary tuberculosis (PTB)
Pulmonary tuberculosis accounts for 60-90% of all cases of TB. It can be further categorized into primary or post-primary (secondary) types. In India, most general physicians encounter pulmonary tuberculosis.
Extrapulmonary tuberculosis (EPTB)
EPTB results from hematogenous dissemination of tubercle bacilli to various organs. Though EPTB constitutes about 10-40% of all the cases of TB, in HIV-positive patients, the frequency is much higher accounting for two-thirds of all cases of tuberculosis.
Tuberculosis lymphadenitis
It is the most common form mainly in children, accounting for 35% of all EPTB cases. The most common sites are posterior cervical and supraclavicular lymph nodes. It presents as painless swelling in the neck region without warmth or colour changes.
Pleural tuberculosis
It accounts for 20% of all EPTB cases. It presents as pleural effusion. Tuberculosis empyema is a less common complication that develops due to rupture of a cavity into pleural space with spillage of tubercle bacilli, which may form a bronchopleural fistula.
Tuberculosis of the upper airways
Involving larynx, pharynx, and epiglottis. Hoarseness, dysphonia, and chronic productive cough are the common clinical presentations.
Genitourinary tuberculosis
Renal tuberculosis
Genital tuberculosis : In female patients, fallopian tubes and the endometrium are commonly involved causing infertility. In males, epididymis is the most common site.
Skeletal tuberculosis
Weight- bearing joints, such as spine, hips and knees are commonly affected.
- With advanced disease, collapse of vertebral bodies results in kyphosis(gibbus) and a paravertebral cold abscess may also form.
- Cold abscess may penetrate the chest wall to present as soft tissue mass, or may penetrate inguinal ligaments and present as psoas abscess.
Tuberculosis of Central nervous system
It occurs commonly in children. Tuberculosis meningitis and tuberculoma are the common forms.
Gastrointestinal tuberculosis
Terminal ileum and caecum are the most common sites involved. The route of spread may be due to swallowing of sputum with direct seeding, hematogenous spread, or ingestion of cow’s milk infected with tuberculosis.
TB peritonitis occurs either by direct spread, ruptured lymph nodes or hematogenous seeding.
Tuberculosis pericarditis
It occurs as direct extension from adjacent lymph nodes or following hematogenous spread. It occurs in elderly people, in countries with low TB prevalence.
Tuberculosis skin lesions
- Scrofuloderma : It is a skin condition caused by tuberculosis involvement of the skin by direct examination, usually from underlying tuberculosis lymphadenitis.
- Lupus vulgaris: Apple jelly nodules are formed over the face in females.
- Miliary or disseminated tuberculosis
Hematogenous spread of tubercle bacilli results in the formation of yellowish 1-2mm size granulomatous lesions resembling millet seeds(thus termed as miliary) in various organs.
Tuberculosis Diagnosis
Diagnosis of active TB:
Specimen collection
Two sputum samples recommended by the general physician are a spot sample (collected on the same day under supervision) and an early morning sample (collected on the next day).
Direct microscopy by acid- fast staining
Ziehl Neelsen (ZN) technique – long slender, beaded, less uniformly stained red colour acid fast staining
CBNAAT
It is used for identification and detection of resistance to rifampicin; it has a turnaround time 2hours. It is based on real-time PCR technique; simultaneously detects : MTB complex DNA, and rifampicin resistance. It used five probes targeting various sequences of rpoB genes. It is a new method. It is widely used for diagnosis of TB . National tuberculosis elimination programme introduced by the government of India. This program for tuberculosis uses CBNAAT as a primary diagnostic tool.