Question

What are the lesions found in the lungs in mycobacterium tuberculosis?

Answer 1

Tuberculosis is caused by obligate aerobic, acid fast bacillus called Mycobacterium tuberculosis. The host resistance levels are affected by various factors and these include presence of other illness, physiological and environmental factors, malnutrition and stress may lead to the infection. The infection is caused by inhaling the bacillus. The bacilli reach the lungs where the alveolar macrophages phagocytize them to destroy the bacilli. But the bacilli usually escape this host defense action because of the mycolic acids that occur in the cell wall of the bacteria stimulate the inflammatory response in the host. The infection is initiated by lesion in the lungs called tubercle. The lesions become calcified and show up Ghon’s complexes in the X-ray films. The tubercle breaks down releasing the virulent bacilli in to the lungs, cardiovascular and lymphatic systems. Coughing is the obvious system of lung infection. Sputum may contain blood because of the tissue damage result in fatal hemorrhaging. The disseminated infection is called miliary tuberculosis.

First effective antibiotic used was streptomycin and was introduced in 1944. The current treatment recommended by world health organization (WHO) requires minimum 6 months of antibiotic therapy including 3 to 4 drugs. Anti T.B drugs like isoniazid and rifampin are mostly administered. Other drugs include pyrazinamide, rifapentine and ethambutol. Diagnosis can be done by tuberculin skin test which is resulted due to sensitized T cells as response of humoral immunity develops in the skin. Other tests like Mantoux skin test and chest X-ray are C.T examination to detect lung lesions are carried out. The BCG vaccine containing the live culture of M.bovis responsible for causing bovine tuberculosis has been made avirulent by long cultivation on artificial media. The BCG vaccine (bacillus of Calmette and Guerin) has been available since 1920 and was found to be effective and new vaccines are also developing to control the multidrug resistant strains