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Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
Mycobacteria - Prac. Microbiology
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Mycobacteria - Prac. Microbiology

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  • 1. MYCOBACTERIA
  • 2. Characters • Acid-alcohol fastness • Slow rate of growth
  • 3. Members of the Genus Mycobacterium 1. Mycobacterium tuberculosis Complex: M. tuberculosis, M. bovis, M. africanum & M. microti. 2. Non-tuberculous mycobacteria (NTM): e.g. M. avium complex & M. fortuitum. 3. Mycobacterium leprae: causes leprosy. 4.The Bacillus of Calmette-Guerin (BCG)
  • 4. Mycobacterium Tuberculosis Morphology: - Acid-alcohol-fast bacillus - Slender - Straight or curved - Arranged singly or in small groups - Ziehl-Neelsen (Z-N) --- pink in a blue background.
  • 5. Lipid-Rich Cell Wall Gram Stain
  • 6. Ziehl-Neelsen (Z-N) Stain • Carbol-fuchsin dye • Heat • Acid-alcohol (decolourization) • Methylene blue • Acid-fast = Mycobacteria
  • 7. Cultural Characters Media include: - Lowenstein-Jensen (L-J) medium - Middlebrook's medium
  • 8. Cultural Characters • Strict aerobe (5 - 10% CO2 stimulates its growth). • Colonies appear after 2-4 weeks of incubation at 37°C and may be delayed to 8 weeks.
  • 9. Human Tuberculosis Mode of Infection Inhalation of droplet nuclei from a patient with open pulmonary tuberculosis. Ingestion of milk contaminated with M. bovis. TB may affect other systems (e.g. TB meningitis, lymphadenitis, renal, genital & intestinal TB).
  • 10. Oral mainfestations of tuberculosis 1. Primary complex 2. Oral ulceration secondary to pulmonary tuberculosis 3. Lupus vulgaris 4. Tuberculous periapical infection and osteomyelitis.
  • 11. Laboratory Diagnosis of Open Pulmonary TB Specimens: include sputum, BAL Early morning sputum specimens collected on 3 consecutive days, from a deep productive cough, give the best results
  • 12. Direct Detection: 1. Smears: Ziehl-Neelsen (Z-N). Under the ordinary light microscope, AFB appear pink in a blue background.
  • 13. 2. Molecular tests: • For rapid detection • Expensive
  • 14. Cultivation: Conventional culture media: (incubated in 5 – 10% CO2 at 37o C): L-J tube - Results may be relatively delayed (2-8 weeks).
  • 15. Fluid Medium Systems (4-14 days identification) Middle brook broth and Bactec AFB media
  • 16. Laboratory Diagnosis of Extra-Pulmonary TB Same as mentioned for pulmonary TB, but by collecting the appropriate specimens. However, specimens collected from normally sterile sites, e.g. CSF, do not require decontamination.
  • 17. Tuberculin Skin Test (TST) Principle: detects a delayed type hypersensitivity (DTH) response to previous exposure of the host to tubercle bacilli.
  • 18. Interpretation of the Tuberculin Skin Test An induration of 10 millimeters or more is considered positive
  • 19. Prevention is Always Better than Treatment 1. General Measures e.g., Pasteurization of milk. 2. Treatment of latent tuberculosis. 3. BCG Vaccine.
  • 20. MCQ Questions 1.M. tuberculosis are characterized by being: a.Strict anaerobes b.Acid fast bacilli c.Capsulated d.Motile e.Able to grow on ordinary media
  • 21. 2.One of the following media is used for growing M. tuberculosis: a.MacConkey’s agar b.Blood agar c.Nutrient agar d.Lowenstein Jensen medium e.Loeffler’s serum
  • 22. 3.The following methods are used in the diagnosis of pulmonary tuberculosis except: a.Examination of ZN stained direct sputum smear b.PCR of sputum c.Culture on selective medium d.BACTEC AFB system e.Detection of specific antibodies
  • 23. Thank You

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