MYCOBACTERIUM TUBERCULOSIS

MORPHOLOGY, PATHOGENECITY AND LABORATORY DIAGNOSIS

INTRODUCTION

• Mycobacteriaceae is the causative agent of tuberculosis.
• First discovered in 1882 by Robert Koch, M. tuberculosis has an unusual, waxy coating on its cell surface primarily due to the presence of mycolic acid.
• The bacteria usually attack the lungs, but TB bacteria can attack any part of the body such as the kidney, spine, and brain.
• If not treated properly, TB disease can be fatal. 

MORPHOLOGY

• M. tuberculosis is a small, Gram-positive, rod-shaped, strictly aerobic, acid-fast bacillus  Acid-fast bacilli are bacilli, which once stained, resist discoloration by acid and alcohol.
• Like other mycobacteria, it is slow growing, resulting in more gradual development of disease when compared with other bacterial infections.
• Under the microscope, the bacillus is seen as a bright red rod, while the surface that it grows on is colored blue.
• Mycobacterium tuberculosis a chemo- organotrophic, non-motile, non-spore-forming bacillus. Grow under optimal laboratory conditions at 37 C, doubles every 24h, taking approximately 3weeks to form buff-coloured, rough colonies on agar plates.

PATHOGENECITY

• Mycobacterium tuberculosis is a human pathogen.
• M. tuberculosis is taken up by alveolar macrophages (Mφ) (step 1) and replicates efficiently (step 2) until the host cells are killed (step 3).
• M.Tuberculosis (TB) is a disease caused by germs that are spread from person to person through the air.
• Bacteria can also enter the body through a break in the skin, such as a puncture wound that gets contaminated with water or soil.
• Tuberculosis most commonly affects the lungs.
• Symptoms include productive cough, fever, weight loss, and malaise.
• The period from infection to development of the primary lesion or significant tuberculin reaction is about 3–9 weeks.

LAB DIAGNOSIS

• The Mantoux tuberculin skin test (TST) or the TB blood test can be
• Broad-range PCR assays followed by postamplification analysis, such as DNA sequencing, used to test for M. tuberculosis infection.

Skin test

• A tiny amount of a substance called tuberculin is injected just below the skin on the inside of one forearm. Within 48 to 72 hours, a health care worker will check your arm for swelling at the injection site. The size of the raised skin is used to determine a positive or negative test.

Blood test

• The blood test finds out whether certain immune system cells can "recognize" tuberculosis. A positive test shows that you have either a latent TB infection or active TB disease. 

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X-ray

• A chest X-ray can show irregular patches in the lungs that are typical of active TB disease.

Sputum tests

• A sample of the mucus that comes up when you cough, also called sputum. If you have active TB disease in your lungs or voice box, lab tests can detect the bacteria.

Other lab tests

• Other lab tests that may be ordered include:
• Breath test.
• Procedure to remove sputum from your lungs with a special tube.
• Urine test.
• Test of the fluid around the spine and brain, called cerebrospinal fluid.

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TREATMENT

• The active TB disease can be treated with a combination of antibacterial medications for a period of six to 12 months.
• The most common treatment for active TB is isoniazid INH in combination with three other drugs—rifampin, pyrazinamide and ethambutol.
• If not treated properly, TB disease can be fatal.

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THANK YOU

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BY

M. JERLINE

Head and Assistant Professor

Department of Biochemistry

Dr.R.A.N.M Arts and Science College

Erode.