Mycobacterium tuberculosis is the bacterium that causes tuberculosis (TB). It is a slow-growing acid-fast rod-shaped bacterium. TB is transmitted through airborne droplets when people with active TB cough, sneeze or spit. The bacteria are able to survive inside alveolar macrophages in the lungs without being destroyed. This can lead to the formation of lesions called tubercles and caseous necrosis, causing the symptoms of TB. Diagnosis involves microscopic examination of samples for acid-fast bacilli, culturing of samples, and radiological examinations. Treatment requires taking a combination of antibiotics for several months.

1. Mycobacterium tuberculosis
Presented to:
Dr. P. Saranraj
Head,
Department of microbiology
Sacred heart college (Autonomous)
Tirupattur
Presented by:
A.R. Deborah (BP211501)
I M.Sc. Applied microbiology
Department of microbiology
Sacred heart college (Autonomous)
Tirupattur

2. Introduction
 Tuberculosis (TB) most probably begins around 70,000 years ago. The humans
and animals was affected by TB.
 The TB which infects respiratory tract and lung tissues.
 In 1882, the causative agent was first described by Robert Koch and named as
“mammalian tubercule bacilli”. It is caused by Mycobacterium tuberculosis (in
humans) and Mycobacterium bovis (in animals) .

3. Morphology
 Mycobacterium tuberculosis is a rod-shaped bacterium which stains poorly by
gram stain because its cell wall contains lipids (mycolic acids) , maybe in pairs or
small clumps.
 It retains carbol fuchsin dye during decolourisation with acid and alcohol in
Ziehl-Neelson staining technique and observed as Red colour Acid fast bacilli.
 Aerobic respiration
 Non-motile
 Non-sporing and non-capsulated
 Generally growth is low, it takes several weeks to form visible colony.

4. Cultural characteristics
 The bacilli grow slowly, the generation time is 14-15 hours. The colonies takes 2
weeks time to appear or more than 4 weeks.
 The optimum temperature is 37 ͦ C, it does not grow below 25 ͦC or above 40 ͦC. The
optimum pH is 5.4-6.5.
 The cultivation of tubercle bacilli have been in both solid and liquid media.
 For solid media Lowenstein-Jensen (LJ) medium is used for Mycobacterium
tuberculosis, this media consist of coagulated hens eggs, mineral salt solution,
asparagine and malachite green act as a selective medium for tuberculosis. M.
tuberculosis forms dry, rough, raised, irregular colonies with a wrinkled surface,
creamy white after some time of incubation it appears in yellowish colour in media.

5. Pathogenesis of tuberculosis
 The infection occur by airborne transmission of droplets nuclei containing a few
viable cells of virulent organisms. These droplet nuclei are the major agents
responsible for tuberculosis.
 After the inhalation of droplet nuclei, the bacilli deposited in the alveolar spaces
of the lungs.
 The tubercle bacilli multiply in the Alveoli.
 In lungs, Mycobacterium tuberculosis is phagocytosed by alveolar macrophages,
but they are unable to kill and digest the bacterium. Its cell wall prevents the
fusion of the phagosome with lysosome, contains host of antibacterial factors.

6. Pathogenesis of tuberculosis
 The alveolar macrophages cells form a barrier shell called Granuloma, that keeps
the bacilli contained and under control.
 If the immune system is weak, the Bacilli multiply rapidly (TB disease) and
enters into the blood stream.
 The blood stream process occurs in different areas in the body like lungs, kidney,
brain.

7. Clinical Diseases by Mycobacterium tuberculosis
 Pulmonary Tuberculosis
This tuberculosis infection commonly involved in lungs. About 25 % of people may
not have symptoms. People may cough blood in small amounts, in very rare cases
the infection may enter into the pulmonary artery (massive bleeding).
 Extrapulmonary Tuberculosis
This infection spreads outside the lungs, causing other kind of Tuberculosis, and
commonly in people with weak immune system and young children. HIV patients
more than 50 % are affected.
 A potentially more serious, widespread form of tuberculosis is called
Disseminated tuberculosis, also known as Miliary Tuberculosis.

8. Clinical Manifestation
 Chronic productive cough
 Pain in chest
 Low-grade fever
 Night sweats
 Fatigue
 Weight loss
 Secretion of sputum (the sputum appears red coloured if blood is mixed with lung
cavity).

9. Laboratory diagnosis
 The collection of samples like sputum, blood, bronchial washings, pleural
fluid and cerebrospinal fluid are collected. The sputum should be collected in
the early morning.
 The microscopic examination such as acid-fast bacilli and motility test and
biochemical test.
 Laboratory diagnosis of tuberculosis includes isolation of acid-fast bacterium,
chest X-ray, gas-liquid chromatography, HPLC test, thin-layer
chromatography, tuberculin skin test and Interferon – γ release tests.

10. Treatment
 The anti-mycobacterial drugs are isoniazid, rifampin, pyrazinamide,
ethambutol and streptomycin was one in the combination.
 Prophylaxis for exposure to tuberculosis can include INH for 6 to 9 months.
 Mostly combined drugs are used for the treatment of tuberculosis, it reduce the
resistant nature of pathogen.
 This combined therapy is administered for 12-24 months.

11. Prevention
 A vaccine for M.tuberculosis is BCG (Bacillus of Calmette and Guerin).
 It is a live vaccine attenuated strain derived from M.bovis.
 This vaccine is not 100 % effective. So it may effective from 60 – 80 % rate in
children.
 Cover the mouth and nose while sneezing and coughing it reduces the spreading
of TB.

12. THANK YOU FOR LISTENING!