Lecture 19 - Tuberculosis Flashcards Preview

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Flashcards in Lecture 19 - Tuberculosis Deck (85)
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0

Which bacteria cause TB?

M. tuberculosis
M. bovis

1

How long has tuberculosis been around?
When was it discovered?

Been around for centuries

Discovered in the 1880s

2

What does infection usually present as?

Chronic pneumonia

3

Describe the onset of TB

Insidious

Slow, eventually getting worse and worse

4

What are the symptoms of TB?

- Cough
- Weight loss
- Fever
- Chills

5

Which organs are affected in TB?

Usually lungs

Other organs can be affected:
- lymph nodes
- brain
- bone
- urinary tract

6

Is TB an important disease?

2nd most common infection after HIV
Third of the world infected
8.8 million deaths in 2010

7

Compare 'infection' and 'disease'

Latent infection: immune system is controlling disease
- no symptoms

Disease: bacteria escape the immune response
- symptoms

8

Can TB causing bacteria be drug resistant?
Talk to this

Yes

This year, there have been completely drug resistant strains reported

Resistance occurs through improper treatment with antibiotics

9

Which parts of the world experience the most TB infection?

Southern half of African continent
Russia
Asia
South east asia

10

How many species are there in the Mycobacterium genus?
Are they all pathogens?

There are many
Most are harmless
Some cause disease

11

What does M. tuberculosis cause?
What is the reservoir?

TB
Humans

12

What does T. bovis cause?
What is the reservoir?

TB
animals

13

What does M. ulcerans cause?
What is the reservoir?

Skin ulcers

Environment

14

What does M. leprae cause?
What is the reservoir?

Leprosy

Humans

15

What does MAC cause?
What is the reservoir?

TB-like disease in AIDS patients

Environmental

16

Are M. bovis infections commonly seen?

Not really anymore

Due to pasteurisation of milk

17

What are the oxygen requirements of M. tuberculosis?

Aerobic

18

What are some of the features of M. tuberculosis?

What are these features due to?

Acid fast
Resistant to drying
Resists killing by macrophages
Resistant to common antimicrobials
Slow growing

Due to the unusual cell wall composition

19

Describe the structure of the cell wall of M. tb

Plasma membrane
Peptidoglycan
Arabinogalactam
Mycolic acids
Superficial lipids
LAM: lipoarabinomannam

20

In one word, describe the cell wall of M. tb

Waxy

21

What can't the gram stain be used to visualise M. tuberculosis?

The cell wall is resistant to other dyes

22

How is M. tuberculosis stained?

Ziehl-Nielsen

1. Carbon fuschin (strong dye) added for 10 minutes
2. Every thing is now pink
3. Decolorise with acid-alcohol
4. Only M. tuberculosis retain the pink dye
5. Everything else counter stained with a blue dye

23

How does M. tuberculosis get into us?

1. Infected person has open lung lesion
2. Infected person coughs / sneezes / talks
3. Droplet nuclei released into air and remain for hours
4. Droplet nuclei inhaled

24

Once inhaled, what happens to M. tuberculosis in terms of immune response?

Avoids mucociliary elevator

Taken up by alveolar macropahages

25

Describe the normal innate response when microbes penetrate into the lower respiratory tract (LRT)

1. Microbe binds to PRR / antibody / C'
2. Phagocytosis by alveolar macrophage
3. Phagolysosome formation
4. Degradation
5. Presentation of antigen on MHC II
6. Release of cytokines

26

What are the different types of droplets?
He long does each stay in the air?

Large droplets: not very long

Small droplets: longer

Droplet nuclei: hours; indefinitely

27

Normally, how are microbes broken down in the phagolysosome?

1. Hydrolytic enzymes
2. Reactive oxygen species (ROS)
3. Reactive nitrogen species (NO)

28

Describe the innate responses in the LTR when droplet nuclei penetrate

1. M. tuberculosis binds to PRR
2. Phagocytosis
3a. Bacterium prevents lysosome fusion with the endosome
3b. Produces ammonium to keep the pH in the phagosome high
4. Survival and replication of the bacterium
5. Some degradation --> MHC II presentation
6. Cytokines release

29

What prevents lysosome fusion with the phagosome?

Mycobacterial lipids