PATHOPHYSIOLOGY OF TUBERCULOSIS: AN UPDATE REVIEW
Devender Sharma*1, Deepika Sarkar1
1Hi – Tech College of Pharmacy, Chandrapur, Maharashtra (India)
Tuberculosis is a hypersensitive granulomatous infectious disease caused by Mycobacterium Tuberculosis (M.TB).In India 40% people are affected by T.B. So need of knowledge about T.B. and pathophysiology of T.B. to people or society. Pathophysiology means, when a human being or animal being suffering from a disease this is because deranged or change in function on that organ or human body. Infection is caused by air- borne droplets of organisms person to person. The main object of this review is how to diagnose and how it is cure or treat. It is diagnosed by PPD, IGRA, Sputum studies, X-rays and Biopsies. Mostly antibiotics are preferred for the first treatment.
Reference Id: PHARMATUTOR-ART-2563
Tuberculosis (TB) is an infectious disease caused by the bacillus Mycobacterium tuberculosis (Mtb). It is the most dangerous bacterial infection responsible for severe increase in death cases. The tubercle bacillus was discovered by Robert Koch in 1882. There are several reports indicating that tuberculosis (TB) is an age old dreadful disease even from ancient times.1 The disease was called "consumption" in the past because of the way it would consume from within anyone who became infected.
Tuberculosis is a chronic granulomatous infectious disease. Infection occurs via aerosol, and inhalation of a few droplets containing M. tuberculosis bacilli. After infection, M. tuberculosis pathogenesis occurs in two stages. The first stage is an asymptomatic state that can persist for many years in the host, called latent TB. (Kaufman, 2014)
In the year 1993, World Health Organization (WHO) declared TB a global public health emergency. About one-third of the world’s population (> 2 billion), are infected with TB bacilli. 10% of the people infected with TB bacilli will become sick with active TB in their lifetime.2,3 According to WHO report, global population with burden of disease caused by TB from 1990-2011 was 6948 million and total number of Multi-Drug Resistant (MDR) cases from 2005-2011 were 61690.3 In 2011, there were an estimated 8.7 million incident cases of TB (range, 8.3 million–9.0 million) globally. Highest numbers of incidences were reported in Asia (59%) and Africa (26%). Estimates of the burden of TB disease among children have also been carried out. The figures are 4,90,000s cases and 64,000 deaths among HIV-negative children per year. TB is one of the leading causes of death among women. 0.5 millions women succumbed to TB. This includes 3, 00,000 (range, 2, 50,000–3, 50,000) TB deaths among HIV-negative women. (Kaufman, 2014)
The burden of TB is highest in Asia and Africa. In 2011, largest number of cases was reported from India, China, South Africa, Indonesia and Pakistan. India and China alone accounted for 26% and 12% of global cases, respectively. Of the 8.7 million TB incident cases reported
in 2011, about 1.2 million people are also suffering from HIV. In the African region, 39% of TB cases were estimated to be co-infected with HIV. (Kaufman, 2014)
Most cases of TB are caused by M. Tuberculosis and the reservoir of infection is humans with active TB.
Most cases of TB are pulmonary and acquired by person to person transmission of air-borne droplets of organisms. Oropharyngeal and intestinal TB contracted by drinking dairy milk contaminated with M. Bovis rarely seen nowadays and usually in countries with tuberculosis dairy cows and unpasturised milk. (Hachart et al., 2016)
Tuberculosis is a common disease prevalent through out the world. It is a chronic specific inflammatory infectious disease caused by Mycobacterium tuberculosis in humans. Tuberculosis usually attacks the lungs but it can also affect any parts of the body. (Alexander et al., 2015)
Etiology of tuberculosis (Alexander et al., 2015)
Mycobacturium tuberculosis–most common cause Other than tuberculosis-includes:
a. M. aviumintracellulare
b. M. kansasi
c. M. scrofulaceum
d. M. marinum
f. M. fortuitum
g. M. chelonei
Sites involved (Hachart et al., 2016)
a. Pulmonary tb-85% of all tb cases
b. Extrapulmonary sites.
c. Lymph node
d. Genito-urinary tract
e. Bones & joints
Characteristics of m. Tb (Alexander et al., 2015)
a. Rod shape, 0.2-0.5 in D, 2-4 in L.
b. My colic acid present in its cell wall, makes it acid fast,
c. So it resists decolourization with acid & alcohol.
d. Aerobic and non motile.
e. Multiplies slowly.
f. Can remain dormant for decades.
How is TB Transmitted (Hachart et al., 2016)
a. Person-to-person through the air by a person with active TB disease of the lungs.
b. Less frequently transmitted by:
1. Ingestion of Mycobacterium bovis found in unpasteurized milk products or autoingestion.
2. Inoculation (in skin tuberculosis).
3. Transplacental route (rare route).
Pathogenesis of tuberculosis (Alexander et al., 2015)
1. M.tuberculosis starts a IV hypersensitivity immune reaction inside the lung which damages the lung tissue while killing the foreign microorganism.
2. Pathologic manifestation of tuberculosis like caseating granuloma and cavitation are result of hypersensitivity that develops in concert with the protective host immune response.
3. Macrophagesare the primary cells infected by M.tuberculosis.
Morphology of Tb
Primary tuberculosis: (Alexander et al., 2015)
1. Form of disease that develops in a previously unexposed person.
2. Almost always begins in lungs.
3. Inhaled bacilli implant in the distal airspaces of lower part of upper lobe or upper part of lower lobe.
4. It forms a small sub pleural parenchymallesion in the mid zone of the lung (ghonfocus inflammation +caseousnecrosis )
5. Tubercle bacilli drain to the regional lymph node which also often undergo caseousnecrosis.
6. Parenchymallung lesion + Nodal involvement= Ghon’scomplex.
Granulomatous inflammation forms both caseating and non caseating tubercles. Tuberculous Granuloma has the following characteristics:
2. Transformed macrophages called epithelioid cells.
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