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
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
EpidemiologySeveral 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 (noninfectious)
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 = 2472 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