Mycobacterium tuberculosis

 Lecture           (13)              

 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

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

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