Mycobacterium tuberculosis

Mycobacterium tuberculosis
Lecture (14)
Dr.Baha, AL-Amiedi
Ph. D.Microbiology
Robert Koch
1843-1910
German physician
Became famous for isolating
the anthrax bacillus (1877),
tuberculosis bacillus (1882)
and cholera vibrio (1883)
First linked M. tuberculosis to
the disease TB, winning the
Nobel Prize in 1905


Tuberculosis - species
Mycobacterium tuberculosis
In immunosuppressed
people, occasionally:
M. bovis
M. africanum
M. microti
M. leprae
Mycobacterium tuberculosis
CHARACTERISTICS
• rod shaped bacteria ,non-spore , cell wall,
Unusually with high glycolipid (mycolic acid)
• Special stain Ziehl-Neelsen (acid-fast stain
required) non-motile
• Aerobic, very slow growth in
Culture Lowenstein-Jonsens medium
• Capable of long-term survival in
the human body (persistence) resistance for heat,drying,germicides and other enviremental factores,perphas because of various lipid in cell wall
Mycobacterium tuberculosis

Transmission and Pathogenesis
TB: Transmition
Infection = Person to Person via Airborne
Infectious Aerosol:
Coughing
Sneezing
Talking

Aerosolized Droplets 5 Micrometers = 1-400
Bacilli
• Estimated 5-200 Organisms Required for infection
Microorganisms and pathogenesis
Virulence Factors
Ability to survive in lung macrophages
• Cell wall components that elicit damage to tissue
• Ability to survive for decades in walled-off lesions
• Difficult to study
Virulence Factors
• Only recently amenable to genetic studies
–
– Microarray Technology and Whole genome transcriptome
(
is used to study the interaction of Mycobacterium tuberculosis with
macrophages.
Cellular constituent:
Vairluent strains have pathogenic components
1-alipid (2mycolic acid it is alarge fatty acid with disaccharide called cord factor),Experimentally inhibit neutrophil migration and damage mitochondria of
The infected host(stain due to mycolic acid)
2- several proteins are present that evoke tuberculin reaction in skin
3..polysaccharide of tubercule bacilli that induce the immediate Hypersensitivity type
(lV)

Pneumonia caused by acid-fast bacterium Mycobacterium
Tuberculosis

•
• Course of infection
– Acquired from organisms inhaled in airborne droplets
– Organisms lodge within pulmonary alveoli
– Cell-mediated immunity develops
– Activated macrophages attack and destroy many of the
organisms
– Characteristic granulomas form
– Infection arrested in majority of cases


Pathogenesis:
T.B is a granulomatous inflammatory disease
Infected macrophages become surrounded by
Tand B lymphocytes and fibroblasts, aggregating
to form a “granuloma”, limiting dissemination
Granulomas can become necrotic in the centre


Primary sight of infection is the lungs
Mycobacterium reach pulmonary alveoli
Replicate within alveolar macrophages
Bacteria enter dendritic cells (do not replicate)
and travel to distant lymph nodes
Enter blood and spread to any organ of the body



• Miliary Tuberculosis
– Mass of tuberculous inflammatory tissue erodes
into a large blood vessel
– Dissemination of organisms by bloodstream
• Extrapulmonary tuberculosis
– Result of hematogenous spread of tubercle
bacilli
– Sites
• Kidneys
• Bone
• Uterus
• Fallopian tubes
Tuberculosis in human body



Epidemiology-
Several factors increase susceptibility to TB and
increase mortality among infected individuals:
HIV / immunosuppression (TB is the most
frequent cause of death in people with HIV)
Smoking (4 fold excess risk
diabities

1/3 World population has been exposed
to the T.B infection
1 new infection per second world-wide
Most infections are latent (non-infectious)
1/10 progress to active TB
Of those, 50% die (1.6-2 million people/yr
Incidence per 100,000: Red>300, Orange 200-300,Yellow 100-200, Green 50-100, Grey<50
Oral aspect of pulmonary tuberculosis
Pulmonary tuberculosis in open form that is actively releasing viable bacilli present in risk to the dentist, dental technical since it releases into the mouth in numerable bacilli, these may found contaminating the lips,gingival ,teeth and oral mucosa membrane as well as saliva.
TUBERCULOSIS
DIAGNOSIS
– Skin test indicates previous exposure to organism
– Chest x-ray indicates pulmonary infiltrate
– Culture identifies organism in sputum
Detection molecular characteristic by:
1-polymerase chain reaction technique
2-high performance liquied chromotography

CXR with evidence of TB infection

TB: Determinants of Disease
Defects in Cell Mediated Immunity*
Advanced Age
Malnutrition
Genetic Factors
Immunosuppressive Meds**
Co-existing Disease: Diabetes
Malignancy
HIV
Renal Failure
TB: Disease Pattern
Primary Tuberculosis




• Reactivation Tuberculosis
TB: Diagnosis
• PPD
• Sputum Examination
• Chest X-Ray
• Culture
T.B: PPD= (Tuberculin skin Test)(Purified Protein Derivative)
The Tuberculin Skin Test Identifies Individuals
Who Have Been Infected With Mycobacterium
Tuberculosis, it Does not Differentiate Between
Old and New Infection
TB: PPD•
Dose of Tuberculin = 5TU
• Injection Site = Intradermally Dorsal Side of
Forearm
• Inflammatory Reaction = 24-72 Hours
• Result Test in 48-72 Hours (If Positive at 6 Days = true positive
Testing for TB Disease and Infection

TB: BCG Vaccination(Bacilli Calmetti Guerin)
Live Attenuated Vaccine Derived From M. Bovis
• WHO: Recommended For Young Children
• Vaccination = 60-80% Decrease in Disease Does
Not Prevent Infection
• Effect of BCG on PPD Decreases With Time
.It given interademally over deltoid region

Principles of Tuberculosis Treatment
Principles of Tuberculosis Treatment
The World health Organization Advocates
Directly Observed Therapy
(DOT)
Drugs in Current Use
Isoniazid
• Rifampin
• Pyrazinamide
• Ethambutol
• Streptomycin
Mycobacterium leprae
It is causative agent of leprosy, it is acid fast bacilli
and it is slightly curved occurring in bundule with characters weakly acid fast stain 5% H2SO4 is used in stain.
Leprosy:
Leprosy is the main disease caused by (M. leprae)
Which differs from all other mycobacterium in that it
Can not be cultured , it is a very chronic disease the organism entirely in intercellular&extracellular.
The lesion fluid of leprosy essentially involved the collar of body such as skin facial nerve the nose and pharynax

The End