Mycobacterium tuberculosis is the bacterium that causes tuberculosis (TB). It is a slow-growing aerobic bacterium with a lipid-rich cell wall containing mycolic acid. TB is transmitted via airborne droplets when people with active TB disease cough, sneeze or spit. Symptoms include cough, fever, fatigue and weight loss. TB is treated with a combination of antibiotics taken over 6-9 months to combat drug-resistant strains. While the BCG vaccine is used in high prevalence countries, it is not recommended in the US due to low risk and variable effectiveness.

1. Mycobacterium tuberculosisMycobacterium tuberculosis
by
Mahmoud Kh. Mahmoud
Soran University
Department of Microbiology
Medical Bacteriology
13 May 2014 Tuesday

2. What is Mycobacterium Tuberculosis
M. tuberculosis and seven very closely related
mycobacterial species (M. bovis, M. africanum, M.
microti, M. caprae, M. pinnipedii, M. canetti and M.
mungi) together comprise what is known as the M.
tuberculosis complex. Most, but not all, of these species
have been found to cause disease in humans. The
majority of TB cases are caused by M. tuberculosis.
M. tuberculosis organisms are also called tubercle
bacilli.
TB is an airborne disease caused by the bacterium
Mycobacterium tuberculosis (M. tuberculosis)

3. Characteristics
Considered as weak Gram positive
Obligate aerobe
Non-spore-forming
Non-motile rod
0.2 to 0.6 x 2-4um
Slow generation time: 15-20 hours
• May contribute to virulence
Lipid rich cell wall contains mycolic acid—50% of
cell wall dry weight

4. Cell Wall Structure
Cell wall composed of mycolic acid, a waxy lipid made of
60-90 carbon atoms
The high concentration of lipids gives these properties:
 Impermeability to stains and dyes
 Resistance to many antibiotics
 Resistance to killing by acidic and alkaline
compounds
 Resistance to osmotic lysis via complement
deposition
 Resistance to lethal oxidations and survival inside
of macrophages

5. Mycobacteia sometimes show branching,
filamentous forms resembling fungal mycelium
Classification
The genus Mycobacterium contains two groups
Obligate parasites
Opportunistic pathogens

6. Taxonomy classification
Kingdom: Bacteria
Phylum: Actinobacteria
Order: Actinomycetales
Suborder: Corynebacterineae
Family: Mycobacteriaceae
Genus: Mycobacterium
Species: Mycobacterium tuberculosis

7. Brief History
Historically known by a variety of names,
including:
Consumption
Wasting disease
White plague
TB was a death sentence
Until mid-1800s, many believed TB was hereditary
1882 Robert Koch discovered M. tuberculosis, the
bacterium that causes TB

8. Diagnosis
Biochemical Test Reaction
niacin accumulation Positive
nitrate reduction Positive
pyrazinamidase activity Positive
urease activity Positive
catalase test Negative (heat-labile)
iron uptake Negative
NaCl tolerance Negative
tellurite reduction Negative

9. Pathogenesis of TB
Infection occurs when a person inhales droplet nuclei
containing tubercle bacilli that reach the alveoli of the
lungs. These tubercle bacilli are ingested by alveolar
macrophages; the majority of these bacilli are
destroyed or inhibited. A small number may multiply
intracellularly and are released when the macrophages
die. If alive, these bacilli may spread by way of
lymphatic channels or through the bloodstream to
more distant tissues and organs (including areas of
the body in which TB disease is most likely to develop:
regional lymph nodes, apex of the lung, kidneys,
brain, and bone).

10. 

11. TuberculosisTuberculosis
M. tuberculosis causes disease (Tuberculosis) in
healthy individuals
transmitted man-man
airborne droplets
Five stages of tuberculosis
Stage 1-5

12. TB Infection TB disease in lungs
MTB present MTB present
Tuberculin skin test positive Tuberculin skin test positive
Chest X-ray normal Chest X-ray usually reveals lesion
Sputum smears and cultures
negative
Sputum smears and cultures positive
No symptoms Symptoms such as cough, fever, weight loss
Not infectious Often infectious before treatment
Not defined as a case of TB Defined as a case of TB

13. Symptoms of TB
Fever
Fatigue
Weakness
Weight loss
Night sweats

14. How is TB treated?
Optimal treatment of TB utilizes a combination of 2
to 3 antibiotics taken over a period of 6 to 9
months. Drug resistant strains of TB are not
uncommon, which is why multiple antibiotics are
used together during treatment. Drugs used most
commonly to treat TB include isoniazid, rifampin,
ethambutol, and pyrazinamide.

15. Is there a vaccine for this TB?
BCG (Bacille Calmette-Guerin) vaccine is an
attenuated vaccine that is used in many countries
around the world where TB prevalence is high. In
the U.S. however, the vaccine is not generally
recommended because of the low risk of infection,
its variable effectiveness, and its interference with
TB skin test reactivity.

16. Thank You For Listening!
Prepared by: Mahmoud Kh. MahmoudPrepared by: Mahmoud Kh. Mahmoud
Soran University
Microbiology Dept.
Medical Bacteriology