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Mycobacteria.ppt - PowerPoint Pr

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									MYCOBACTERIA
       MYCOBACTERIUM
• Aerobic bacilli     –non spore forming
                        non motile
• Cell wall         –rich in lipids
• Acid-fast bacilli
• Very slow growing
      MYCOBACTERIA ASSOCIATED WITH
            HUMAN DISEASE
Mycobacterium    Environmental contaminant   Reservoir
M tuberculosis   No                          Human
M bovis          No                          Human, cattle
M leprae         No                          Humn
M kansasii       Rarely                      Water, cattle
M marinum        Rarely                      Fish, water
M scrofulaceum   Possibly                    Soil, water
M avium          Possibly                    Soil, water, birds
intracellulare
M ulcerans       No                          Unknown
M fortuitum      Yes                         Soil, water, animals
M chelonae       Yes                         Soil, water, animals
           CLASSIFICATION OF MYCOBACTERIA
           ASSOCIATED WITH HUMAN DISEASE
Mycobacterium              Clinical significance   Pigmentation      Growth
Unclassified
M Tuberculosis , M bovis   Strict pathogens        No                No
M ulcerans
M leprae                   Strict pathogen         -                 -
Runyon Group 1
M marinum , kansasii       Usually pathogenic      Photochromogens   slow
Runyon Group 2
M scrofulaceum             Rarely pathogenic       Scotochromogens slow
Runyon Group 3
M avium intracellulare      Pathogenic in    No                      slow
                           immunocompromised
Runyon Group 4
M fortuitum, M chelonae    Rarely pathogenic       No                ‘rapid’
Mycobacterium tuberculosis
•   Causes tuberculosis
•   Classic human disease
•   Pathogenesis
•   Transmission
•   Clinical presentations
•   Diagnosis
•   Treatment
•   Prevention
                   Pathogenesis
• Inhaled aerosols
             Engulfed by alveolar macrophages
             Bacilli replicate
             Macrophages die
• Infected macrophages migrate               local lymph nodes
• Develop Ghon’s focus            Primary complex
• Cell mediated immune response

      stops cycle of destruction and spread
• Viable but non replicating bacilli present in macrophages

EVIDENCE OF INFECTION WITH M TUBERCULOSIS
        Chest x-ray / positive skin test
        CLINICAL PRESENTATION
           Pulmonary tuberculosis

               Primary complex
                Asymptomatic
HEALS

         Acute pulmonary disease    REACTIVATION
             Systemic spread         Post-primary
        Aymptomatic /symptomatic     tuberculosis

 LATER DISEASE            MILIARY TUBERCULOSIS
   Renal / CNS etc              Pulmonary
                                meningitis
                    DIAGNOSIS
          Pulmonary tuberculosis

  1        1 Primary complex
              Asymptomatic
HEALS
                                           2
                3
         Acute pulmonary disease    REACTIVATION
             Systemic spread         Post-primary
        Aymptomatic /symptomatic     tuberculosis

 LATER DISEASE            MILIARY TUBERCULOSIS
 3 Renal / CNS etc              Pulmonary   3
                                meningitis
                     DIAGNOSIS
1. Evidence of infection
  a. Chest x-ray - hilar lymphadenopathy
                   calcification of primary focus/LN
  b. Delayed hypersensitivity response to purified protein
     derivative (PPD) MANTOUX /HEAF TEST
2. Evidence of active disease
  a. Sputum for AFB      positive
3. Evidence of active disease
  a. Indirect evidence of infection   (Mantoux)
  b. Direct evidence of infection     PCR / culture
  c. Histo-pathological evidence
              TREATMENT
• Anti-tuberculous drugs
  –   INAH
  –   Rifampicin
  –   Ethambutol
  –   Pyrazinamide
• DOT
• Multi-drug resistant tuberculosis
                  PREVENTION
• Incidence declined before availability of anti-
  tuberculous drugs
• Improved social conditions       - housing /nutrition
• Case detection & treatment
• Contact tracing
• Evidence of infection / disease
• Treatment of infected / diseased contacts

            ROLE OF IMMUNIZATION
          BCG (bacillus Calmette Guerin)
              Mycobacterium leprae
•   Acid fast bacilli
•   Strict human pathogens
•   Cannot be cultivated in-vitro
•   Armadillo’s used for obtaining M leprae
•   Transmission - ? Air borne
•   Low infectivity - prolonged contact required
•   Spectrum of clinical presentations
    – dependent on host –parasite interactions
                 Borderline       Borderline
Tuberculoid                                      Lepromatous
                Tuberculoid      lepromatous
Non tuberculous mycobacteria
M KANSASII

      Infection of respiratory compromised hosts
        Present like pulmonary tuberculosis
       Treatment – resistant to anti TB drugs


 M SCROFULACEUM

         Infection of cervical lymph nodes
       Presents as cervical lymphadenopathy
              Treatment – surgery
Non tuberculous mycobacteria
M avium intracellulare       Immuno competent host

        Infection of cervical lymph nodes
        Presents as cervical lymphadenopathy
        Treatment – surgery

M avium intracellulare         Immuno deficient host

                    severe RTI
      AIDS       severe GI infection
                   septicaemia
Non tuberculous mycobacteria
  M ulcerans

          ‘Burundi’ ulcer
          Prolonged incubation required for growth



 M fortuitum / M chelonei

              Injection related abscesses
        Associated with sternal wound infections
            following cardo-thoracic surgery

								
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