mycobacterium tuberculosis

Mycobacterium tuberculosis
Lecture (12)
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. lepra.
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

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
• Whole genome of the pathogen is sequenced
– 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 VI
t
Pneumonia caused by acid-fast bacterium Mycobacterium
Tuberculosis
Granulomatous inflammation
• 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


TUBERCULOSIS
• 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




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

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(PCR)
2-high performance liquied chromatography-
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
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


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




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