Tuberculosis Parts I

Question 1

Describe the Mycobacterium Tuberculosis organism

Answer 1

Unique cell wall- waxy with high lipid content–> hydrophobic
* Cell wall contains up to 60% mycolic acids – long chain fatty acids
* Responsible for unique staining characteristics of mycobacteria

This would normally remove stain from ordinary bacteria
* But mycobacteria hold onto the stain  they are ACID AND ALCOHOL – FAST

fast meaning it wont change.

Question 2

d explain why it is called an AFB (Acid-fast bacillus?

Answer 2

This would normally remove stain from ordinary bacteria
* But mycobacteria hold onto the stain  they are ACID AND ALCOHOL – FAS

Question 3

Describe the cause of TB

Answer 3

organism called Mycobacterium tuberculosis* complex

Question 4

attenuated

Answer 4

means lessened or weakened

Question 5

caseous

Answer 5

looks like cheese and smell

Question 6

Tuberculosis

Answer 6

is caused by organism call mycobacterium tuberculosis.

Question 7

Why are mycobacteria more resistant to drying?

Answer 7

are characterized by unique cell wall structures that contribute to their resistance to various environmental stresses, including drying. The distinctive features of mycobacterial cell walls and their physiological adaptations enable them to survive and persist in diverse environmental conditions, resist desiccation, and maintain viability under unfavorable conditions for extended periods.

Question 8

chronic inflammation

Answer 8

takes long
* Involves different cell types, namely lymphocytes, plasma cells and especially macrophages
lead to granulation and scar tissue.

Question 9

name one cause of chronic inflammation?

Answer 9

infection with mycobacteria and other that are resistant to phagocytosis and intracellular killing.

Question 10

Inflammation caused by mycobacteria is called ?

Answer 10

granulomatous inflammation

Question 11

The primary host cell of TB in humans

Answer 11

Macrophages

Question 12

The mechanism of action of TB

Answer 12

1.Intracellular pathogen
2. Primary host cell in humans is the macrophage
3. Require cell mediated immunity to control infection
4. Characteristic pathological feature of tuberculosis is granulomatous inflammation or the
formation of necrotising granulomas
5. Potentially lifelong

Question 13

what type of hypersinsitivity TB is

Answer 13

Type 4

associated with a Type IV hypersensitivity reaction, which is a delayed-type hypersensitivity (DTH) reaction mediated by T cells, particularly CD4+ T cells and CD8+ T cells, rather than antibodies (as seen in Type I, II, and III hypersensitivity reactions). The Type IV hypersensitivity reaction in TB is primarily directed against Mycobacterium tuberculosis antigens, leading to the recruitment and activation of macrophages, granuloma formation, and tissue damage in the lungs and other affected organs.

Question 14

pathogenesis of TB?

Answer 14

Occurs on first exposure to TB bacilli
* Following inhalation TB bacilli are phagocytosed by alveolar macrophages
* Normally phagocytosis leads to killing of micro-organism that has been engulfed
* But TB bacilli manage to upset this normal killing: they are not killed and in fact TB bacilli can multiply inside
macrophages
* Inside macrophages TB bacilli are transported via lymphatics to regional (hilar) lymph nodes
* In the lymph nodes TB bacilli stimulate an immune response, mainly by the cell mediated immune response :
* Infected macrophages present TB antigen to lymphocytes
* TB-specific lymphocytes proliferate and produce various cytokines including
* Interferon-gamma
* Tumour necrosis factor (TNF)
* Cytokines activa

Question 15

A granuloma consists of :

Answer 15

Central area of necrosis
* Surrounded by activated macrophages (some of which may fuse together to form giant
cells) Note activated macrophages also called epitheliod cells
* Surrounded on outside by T lymphocytes and fibrous tissue
* The granuloma contains the organism by walling it off

Question 16

Outcome of primary infection: usually healing?

Answer 16

In most cases the tubercles /small granulomas heal spontaneously
* Sometimes form a scar or even calcify
* May show up on CXR as nodule especially if calcified

Question 17

Latent TB

Answer 17

TB that is not killed initially, remain dominant and inactive. become active at a later stage.

Question 18

Secondary Tubercolosis

Answer 18

is due to reactivation of the primary dominant mycobacterium.

Question 19

what are the usual cause of secondary TB

Answer 19

because of declining immune system due to
HIV
MALNUTRITION
Chemotherapy for treatment of malignancy
* Other immunosuppressive medication, e.g. high dose steroids, medication to prevent
rejection after organ transplant, people being treated with anti-TNFα medicines
* Old age

Question 20

Site of the lung where the reactivation of the secondary TB take place

Answer 20

The apex of the lung

Question 21

why does reactivation takes in the apex of the lung???

Answer 21

possibly because this region is more highly oxygenated than elsewhere
* allowing the mycobacteria to multiply more rapidly.

Question 22

in secondary disease the lung gets ?

Answer 22

granulomas and caseous necrosis.

Question 23

complication of TB

Answer 23

The most frequent complications are intrapulmonary or
pleural spread.

Question 24

Miliary TB

Answer 24

So called because the small tubercules of uniform size look like grains of millet
* Uniform/same size because all spread happened at the same time.

Question 25

does Milliary TB occurs on sec or primary

Answer 25

• Occurs in either primary or secondary TB when there is severe impairment of host
  resistance
• Get widespread dissemination of disease with lots of small granulomas in many organs