1. Mycobacteria - Acid Fast Bacilli (AFB)
Tuberculosis (TB) is a chronic granulomatous infectious disease caused by Mycobacterium tuberculosis
it can affect any part of the body including the oral cavity. Extrapulmonary TBis rare,
he mode of spread of tuberculous infections isthrough airborne particles, when an infectious patient coughs, sneezes, talks or sings.
OPTO 435, Lecture 7

2. Mycobacterium tuberculosis
Very thin , rod shape.
Aerobic, need high levels of oxygen to grow.
Non-motile.
Non-spore forming.
Acid-fast rods  it has unusual cell wall, rich in lipids; which makes it:
Difficult to stain with gram stain (not gram positive or negative).
Resist decolorization by acidified alcohol used in gram stain.
Hence acid-fast staining technique is used instead (Ziehl-Neelsen stain)

3. Mycobacterium tuberculosis
It divides every hours, colonies may be visible in up to 60 days; which is extremely slow compared to other bacteria.
It can withstand weak disinfectants, and survive dry state for weeks.
It can be killed by heat or ultraviolet radiation.
The acid fastness of this organism enable us to distinguish them from other genera.

4. M. tuberculosis .
Red bacilli against a blue background

5. Mycobacterium tuberculosis
Laboratory Diagnosis:
Microscopy:
Looking for Acid Fast Bacilli using special stain such as Ziehl- Neelsen.

6. Mycobacterium tuberculosis
Culture:
Culturing of organism:
This is the definitive identification of M.tuberculosis.
It usually grow after 6-8 weeks of cultivation on Lowenstein-Jensen medium (this media have malachite green which prevent growth of most other contaminant)

7. Mycobacterium tuberculosis - Epidemiology
It is the cause of tuberculoses.
Currently about 1/3 of world’s population is infected with M.tuberculosis, 30 million people have active disease.
M.tuberculosis can grow in macrophages and remain viable for decades.
After being inhaled, mycobateria reach the alveoli in the lungs and it multiply in the tissue macrophages. The bacilli that are not destroyed by the immune system will spread to extra-pulmonary sites.

12. Mycobacterium tuberulosis - Pathogenicity

13. The organism capable of intracellular multiplication in the MQ
Often the host unable to eliminate the org-- result in systemic hypersensitivity 2 mycobacterium Ag
1-Granuloma or tubercle forms in the lung from lymphocytes, MQ and cellular pathology including gaint cell formation
2-If the mycobacterium Ag is high the hypersensitivity reaction may lead to tissue necrosis
3-in some patients the disease may spread via the blood or lymph sys leading to disseminated tuberculosis

14. Mycobacterium tuberculosis
Tissue damage is by tubercles which are small granulomata of epithelioid cells and macrophages as multinucleated giant cells.
Central cheesy necrosis is called caseation.

17. ClinicalSignificance
A mode of transmission
Spread through the air by inhaled droplet nuclei.
Transmission can occur from an infectious TB case by coughing, sneezing, or laughing.
Spread mainly through lymphatic and rarely through hematological spread
Usually mild or asymptomatic
B- Primary disease or tubercle formation.
Primary means active TB infection in lungs or other sites
Tubercle may forme (80%) focal granuloma.
Caseous (cheesy necrosis)
C-Primary tuberculosis follows one of two courses.
Tubercles  fibrosis and calcification.
Lesion breaks down  spread of infection.
D-reactivation of tuberculosis.
Caused by M. tuberculosis
Mostly in pulmonary sites.
Usually due to impairment in immune status (malnutrition, alcoholism, advanced age or severe stress).

20. Appendix 12 - Fundamentals of TB Presentation
Latent TB Infection (LTBI)
Immune system keeps bacilli contained
and under control
Person is not infectious and has no
symptoms

21. Appendix 12 - Fundamentals of TB Presentation
TB Disease
Occurs when immune system cannot
keep bacilli contained
Bacilli begin to multiply rapidly
Person develops TB symptoms

22. Appendix 12 - Fundamentals of TB Presentation
LTBI vs. TB Disease
LTBI
TB Disease
Tubercle bacilli in the body
TST or QFT-Gold® result usually positive
Chest x-ray usually normal
Chest x-ray usually abnormal
Sputum smears and cultures negative
Symptoms smears and cultures positive
No symptoms
Symptoms such as cough, fever, weight, loss
Not infectious
Often infectious before treatment
Not a case of TB
A case of TB

24. Appendix 12 - Fundamentals of TB Presentation
Sites of TB Disease
Pulmonary TB occurs in the lungs
85% of all TB cases are pulmonary
Extrapulmonary TB occurs in places other than the lungs, including the:
Larynx
Lymph nodes
Brain and spine
Kidneys
Bones and joints
Miliary (disseminated) TB occurs when tubercle bacilli enter the bloodstream and are carried to all parts of the body

25. Tuberculosis of the Conjunctiva
It is uncommon.
Usually in young people.
It may or may not be associated with systemic tuberculosis.
Usually there is lymph glands involvement.
Treatment:
Streptomycin drops.
Systemic anti-tuberculous therapy (minimum of 6 month).

26. Mycobacterium tuberculosis
Prevention:
BCG vaccine (80% protective).
It is given to children at countries at risk.
Individuals under heavy risk of infection, such as special groups of health-care workers.
Tuberculin skin test:
It is done to see if you have ever been exposed to tuberculosis (TB)
The test is done by putting a small amount of TB protein (antigens PPD) under the top layer of skin on your inner forearm. If you have ever been exposed to the TB bacteria (Mycobacterium tuberculosis), your skin will react to the antigens by developing a firm red bump at the site within 2 days

27. Tuberculin Skin Test (TST)
intradermal injection of 0.1 ml of purified protein derivative (PPD) in the forearm, just beneath the surface of the skin.
The reaction to the TST should be read 48 to 72 hours after the injection
(Source: CDC, 2013e.)

28. Reading the Tuberculin Skin Test
Correct:
only the induration is being measured
Incorrect:
the erythema is being measured.
(Source: CDC, 2013e.)

29. Interpreting TST Reactions
Skin test interpretation depends on the measurement of the induration and the individual’s risk of being infected with TB or progression to disease if infected

31. Appendix 12 - Fundamentals of TB Presentation
Sputum Collection
Sputum specimens are essential to confirm TB
Specimens should be from lung secretions, not saliva
Collect 3 specimens on 3 different days
Spontaneous morning sputum more desirable than induced specimens
Collect sputum before treatment is initiated

32. Appendix 12 - Fundamentals of TB Presentation
Smear Examination
Strongly consider TB in patients with smears containing acid-fast bacilli (AFB)
Use subsequent smear examinations to assess patient’s infectiousness and response to treatment

33. Appendix 12 - Fundamentals of TB Presentation
Culture
Used to confirm diagnosis of TB
Culture all specimens, even if smear is negative
Initial drug isolate should be used to determine drug susceptibility

34. Treatment of TB Disease
Appendix 12 - Fundamentals of TB Presentation
Treatment of TB Disease
Include four 1st-line drugs in initial regimen
Isoniazid (INH)
Rifampin (RIF)
Pyrazinamide (PZA)
Ethambutol (EMB)
Adjust regimen when drug susceptibility results become available or if patient has difficulty with any of the medications
Never add a single drug to a failing regimen
Promote adherence and ensure treatment completion

35. Mycobacterium leprae Skin scraping will show the acid-fast bacilli
Bacteria difficult to culture.
PCR techniques not very sensitive.
Diagnosis is based on clinical manifestation of the disease:

36. Mycobacterium leprae
It is very rare disease, found in tropical countries.
Low infectivity, prolonged close contact & host immunologic status play a role in infectivity.
Transmission occurs person to person through inhalation or contact with infected skin.
The immune response of the host is responsible for the damage to the skin and nerve.

37. Leprosy
Leprosy:
Is is a chronic disease of the skin, mucous membranes and nerve tissue
Etiology:
Mycobacterium leprae.
Leprosy involves predominantly the anterior uvea and may manifest as:
Chronic iritis due to direct invasion of the bacteria of the iris.
Acute iritis may occur and is manifested by intense exudative reaction.

38. Self read topics Mycobateria tuberculosis Epidemiology: Pathogenicity:
Immunity:
Clinical Significance (all phases of the disease a,b,c,d)
Tuberculin reaction.
Laboratory Identification.
Prevention.