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.

10. 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).

11. Oral mainfestations of tuberculosis
1. Primary complex
2. Oral ulceration secondary to pulmonary
tuberculosis
3. Lupus vulgaris
4. Tuberculous periapical infection and osteomyelitis.

12. 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

13. Direct Detection:
1. Smears:
Ziehl-Neelsen (Z-N).
Under the ordinary light
microscope, AFB
appear pink in a blue
background.

14. 2. Molecular tests:
• For rapid detection
• Expensive

15. Cultivation:
Conventional culture media:
(incubated in 5 – 10% CO2 at
37o
C):
L-J tube
- Results may be relatively
delayed (2-8 weeks).

16. Fluid Medium Systems
(4-14 days identification)
Middle brook broth and Bactec AFB media

18. 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.

19. Tuberculin Skin Test
(TST)
Principle:
detects a delayed type
hypersensitivity (DTH)
response to previous
exposure of the host to
tubercle bacilli.

20. Interpretation of the Tuberculin Skin Test
An induration of 10 millimeters or more is considered
positive

21. Prevention is Always Better
than Treatment
1. General Measures
e.g., Pasteurization of milk.
2. Treatment of latent
tuberculosis.
3. BCG Vaccine.

22. 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

23. 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

24. 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

25. Thank You