OVER VIEW OF TUBERCULOSIS “IS IT DISEASE OF PAST DECADE?”

WHAT IS TUBERCULOSIS?
Tuberculosis is a contagious infectious disease. Mycobacterium bacillus / Tubercle bacillus is causative agent for TB infection. Tuberculosis is not the disease of past decade but nowadays, it prevalence is increasing in the world due to factors mentioned below,

FACTORS RESPONSIBLE FOR INCREASE NUMBERS OF TB CASES IN THE WORLD
• In developing countries, it is a life threatening disease due to poor hygienic condition and dense population in which people live very close to each other .
• Immune compromised patient like HIV and AIDS are more prone to get TB infection primarily because of compromised immunity.
• New strain of bacillus is resistant to conventional antibiotics which is also a major contributing factor of TB prevalence 
Lets break down some information about Mycobacterium Bacillus, the route of TB infection, active and inactive TB, types of TB and pathogenesis of TB as follows,

WHAT IS MYCOBACTERIUM BACILLUS?
Mycobacterium bacillus is a gram positive, non-motile, non-spore forming, rod shape and highly aerobic bacteria which require high concentration of oxygen for its metabolism due to which it attacked the lungs first. Although, it can affect any part of body but primarily highly oxygenated areas of body are the first targeted areas. It envelops (cell wall) due to which exhibits the strong features of gram-negative bacteria cell wall. The outer most layer of cell wall has high content of MYCOLIC ACID which has a great role in the pathogenesis of TB. Its replicates slowly unlike the others bacteria which show division rate after every 20 minutes. Mycobacterium bacillus show division rate after every 18-24 hours. It is a facultative intracellular bacterium which means to live in more than one environmental condition.

ROUTE OF INEFCTION
It spreads through the cough, sneeze, talking of infected person as minute droplets in the air which carry live Mycobacterium bacillus in it. After entering into healthy person body as minute droplet, a war is set up between the body defensive army and the Mycobacterium bacillus. If body defensive army defeat the TB bacteria, then bacteria will remain dormant position in the body but if a person defensive system is weak then pathogenesis of TB will start.

PATHOGENESIS OF TUBERCULOSIS
Tubercle bacilli cause a peculiar (unusual) tissue reaction in the lungs which includes the following steps,
1. Mycobacterium bacillus is an invader who after entering into body infect the tissues of lungs then there will be invasion of the infected tissue by macrophage (defensive army of body).
2. Due to immune system of body Mycobacterium bacillus trapped in tissue of body which is surrounded by immune cells which is WALLING OFF of a lesion by fibrous tissue to form the so-called tubercle (hard nodular substance). This walling off process helps to limit further transmission of the Mycobacterium bacillus in the lungs and therefore, it is part of protective process against the extension or spread to the infection. At this stage, TB is called INACTIVE TUBERCULOSIS or LATENT TUBERCULOSIS.

WHAT IS LATENT TUBERCULOSIS?
In LATENT TUBERCULOSIS, the patient is asymptomatic (showing no symptoms of TB) and patient cannot spread the infection to others because Mycobacterium bacillus is in dormant (sleeping) position.  In LATENT TUBERCULOSIS, host (body defensive system) is dominate over pathogen. As we already discussed, Mycobacterium bacillus is facultative intracellular bacteria who escape the body defense mechanism and persists in relatively lower acidic condition with in host macrophage. When person immunity become compromised or LATENT phase TB untreated then walling off process fails and Mycobacterium bacillus spread throughout the lungs and showed ACTIVE TUBERCULOSIS.

WHAT IS ACTIVE TUBERCULOSIS?
In ACTIVE TUBERCULOSIS, the pathogen (Mycobacterium bacillus) become dominate over host defensive system. Now the patient shows all symptoms of TB which are persistent cough, fever, weight loss. Now the patient can spread infection through coughing, sneezing and talking.

HOW MYCOBACTERIUM BACILLUS SPREAD TO OTHER PARTS OF BODY?
From the lungs, Mycobacterium Bacillus can infect any part of body because they get their way (enter) into blood or lymphatic system and through these channels they can infect any part of body.

HOW OCCURRENCE OF CNS TUBERCULOSIS CAN BE PREVENTED?
Early treatment of lung tuberculosis will be helpful in prevention of CNS and other type of TB prevalence.

TYPES OF TUBERCULOSIS
Beside the LATENT and ACTIVE TUBERCULOSIS, TB can be classified on the basis of body part which gets infected as follows,
• PULMONARY TUBERCULOSIS
In this type of TB, lungs are infected.
• PLEURAL TB
In this type of TB, there is accumulation of fluid in pleural space of lungs (space between lining of lung and lung tissues).
• EXTRA PULMONARY TUBERCULOSIS
In this type of TB, infected site is other than lungs which are the other parts of body. It can be classified as,
• MILIARY TUBERCULOSIS
It is rare form of TB and fatal one. It’s affected all over body parts. It is also known as DESSIMNATED TUBERCULOSIS.
• PERICARDITIS TUBERCULOSIS
In this type of TB, pericardium of heart (thin sac like tissues surrounded the heart) gets infected. There is inflammation of pericardium.
• SKELETAL TUBERCULOSIS
There is involvement of bones and joint. Osteomyelitis and arthritis are also observed.
• POTT TUBERCULOSIS (SPONDYLITIS)
In this type, spinal cord gets infected. Different vertebrae of spine are infected.
• GASTROINTESTINAL TUBERCULOSIS
It affected gastrointestinal tract and exhibits abdominal pain and bleeding problem.
• LIVER OR HEPATIC TB
Infected part of body is liver.
• GENITOURINARY TUBERCULOSIS
Involve urinary tract and genital (reproductive) parts of body.
• CNS TUBERCULOSIS
CNS tuberculosis mainly include tuberculous meningitis which is followed by tuberculoma, tuberculosis brain abscess and hydrocephalus (a complicated disease requires surgical intervention along with medical treatment).

WHAT IS BCG VACCINE AND ITS EFFICACY AGAINST PREVALENCE OF TB?
BCG vaccine is live attenuated vaccine derived from Mycobacterium Bovis. It is not as effective as it should be in stopping TB prevalence. Despite of it, it is given to newly born babies immediately after birth especially in under development countries where TB is infection is very common. As we know that children immunity is under development therefore, with BCG vaccine many serious complications of TB can be prevented especially tuberculous meningitis which is fatal one in children. BCG vaccine is not effective against adult against pulmonary TB due to which it is not given to adult patients. However, health care workers who are at great risk of developing TB due to any reason are being vaccinated with BCG vaccine.

TREATMENT OF TUBERCULOSIS
If someone has LATENT TB, then treatment is daily single dose of Isoniazid (INH) for 6 to 9 months but if TB is active tuberculosis, then Isoniazid (INH) is prescribed along with 3 more medication which are ethambutol, pyrazinamide and rifampin/ rifabutin. If first line treatment fails then moxifloxacin, ciprofloxacin and bedaquiline are prescribed.

CONCLUSION
In short, TB prevalence is increasing because of drug resistance compromised immunity, patient non adherence to treatment and unavailability of effective vaccine. Now, it is no more the disease of past decade but in future, there will be further increase in the number of tuberculosis cases.