Q: I was diagnosed for tuberculosis (TB) using a Mantoux or PPD test. The results showed swelling greater than 22 mm. My doctor confirmed me positive for TB. I used to smoke 10-12 cigars a day but have stopped it now. Is TB curable? How can TB be treated effectively?

A:Tuberculosis is caused by a bacterium called Mycobacterium tuberculosis (very rarely due to Mycobacterium bovis or Mycobacterium africanum). The bacterium is very hardy and can survive under adverse environmental conditions. Humans are the only known reservoirs for M tuberculosis. TB occurs when an individual inhales bacteria, which have been aerosolised by infected persons (droplet infection). This infective droplet is very small (<5 mm), may contain approximately 1-10 bacilli and can remain suspended in the air for a prolonged period of time. Although theoretically it is possible for even a single organism to cause disease, about 5-200 inhaled bacilli are usually required to cause infection. The primary infection is of the respiratory tract due to inhalation of infected droplets. The chances of infection increase in small, enclosed spaces and in areas with poor ventilation. Following inhalation, the bacteria are ultimately deposited in the terminal part of the respiratory tract – alveoli or the distal respiratory bronchiole where they are ingested by cells called alveolar macrophages. These cells are unable to kill the bacteria and the organism continues to multiply. The organism is then transported to the neighbouring lymph nodes by the infected cells. There is also the possibility of the bacteria spreading via the blood (or lymph) to other lymph nodes and distant parts of the body like bone, brain, kidney etc. The occurrence of lung infection with involvement of the draining lymph node is called a primary complex. Most infected persons do not develop active disease and the bacillus grows slowly or may remain inert for months to years before getting reactivated, and causing disease. People who have lowered immunity like children and elderly, patients on steroids or chemotherapy or diseases like HIV, malnutrition, etc have a higher risk of developing TB. The definitive diagnosis of TB depends on demonstration of the organism (stained smears &/or culture) from secretions or biopsy tissues. Appropriate specimens include sputum, gastric lavage, bronchoalveolar lavage, lung tissue, lymph node tissue, bone marrow, blood, liver, cerebrospinal fluid (CSF), overnight urine, and stool, depending on the location of the disease. X-ray of the chest is a classic diagnostic tool when evaluating patients for pulmonary TB. It is difficult to comment on a Mantoux test alone. The disease is completely curable. Most patients are given 4 drugs thrice weekly for 2 months followed by 2 drugs thrice weekly for 4 months. Please consult a chest specialist.