Infection & Immunology Julie Letchford Flashcards Preview

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What microorganism is TB caused by? Which organ does it infect preferentially?

Myobacterium tuberculosis,
The lungs

1

TB is a major opportunistic infection in ___ patients

HIV and Aids patients

2

The incidence of Tb is increasing by __% each year
It kills ___ million each year

5%
3 million

3

Mycobacterium tuberculosis. Fast or slow growing? What kind of bacteria?

Slow growing so takes a while to develop the infection
Bacillus

4

The mycobacterium tuberculosis cell wall is rich in lipids. What does this result in?

Very hydrophobic therefore resistant to drying and to weak disinfectants

5

What's the mycobacterium tuberculosis complex?

M tuberculosis
M bovis
M africanum
And M microti

A group of genetically related mycobacterium species that can cause tuberculosis

6

What is stage 1 of the progression of primary TB?

Bacilli is inhaled in droplets (respiratory droplets from someone)
Then phagocytosed by macrophages non specifically
These do not destroy the bacilli!

7

What is stage 2 of the progression of primary TB?

Mycobacterium TB multiplies inside macrophages for 7-21 days
Macrophages burst
Other macrophages may phagocytose the released TB

8

What happens at stage 3 of the progression of primary TB?

Cell mediated response initiated
T cells and B cells and collagen fibres (show up well on X-ray) all accumulate
Tubercules form with a caseous necrosis centre of dead matter

9

Once the Tubercules are formed at stage 3 of TB progression, what three ways may the infection now go?

Infection cleared away by immune system
Infection lies dormant and deactivates at later date (latent)
Progressive infection

10

What happens at stage 4 of TB progression?

Bacteria multiply inside macrophages and there's uncontrolled lysis (bursting)
Enzymes get released and destroy local tissue forming lesions

11

What can we see on an X-ray of TB?

White lesions formed from enzymes from broken down macrophages replace alveoli with scar tissue.
Collagen fibres show up well

12

What is the tuberculin skin test?

Tuberculin is injected into forearm
A positive result: skin lesion (red region) over 10mm diameter forms after 48-72 hours.
Tuberculin is a protein derived from the TB bacteria

13

To treat TB first line we tend to treat with ____ antibiotic drugs in one go

FOUR
Stops all the bacteria becoming resistant as there's so many, if we used just one could easily become resistant

14

What are the four first line anti TB drugs?

Rifampicin
Isoniazid
Pyrazinamide
Ethambutol

15

Describe the effects of rifampicin on TB

Bactericidal- kills off dividing cells, inhibits RNA polymerase
Taken orally, fully absorbed
Decreased effects by food.

16

What are the side effects of rifampicin?

Liver damage
Hypersensitivity
Decreased activity of other drugs
Red coloured body fluids (red wee)

17

Describe the characteristics of anti TB drug Isoniazid

Bactericidal or bacteriostatic
It's a prodrug
Decreases synthesis of mycolic acid
Usually oral, but can be IV or IM

18

What are the side effects of anti TB isoniazid

Hypersensitivity
Peripheral neuropathy
Liver toxicity
Decreased effects of hormonal contraceptives

19

Describe anti TB pyrazinamide

Bactericidal prodrug
Decreases synthesis of mycolic acid
Damages the bacterial membrane
This is the only drug that can truly kill dormant bacteria
Well absorbed orally

20

What are the side effects of anti TB drug pyrazinamide?

Joint pain
Liver damage
Hypersensitivity

21

How does anti TB drug ethambutol work?

Bacteriostatic
Increases permeability of bacterial cell walls
Orally well absorbed
50% excreted unchanged in urine

22

What are the side effects of anti TB drub Ethambutol?

Optic neuritis (blurring, but reversible)
Joint pain
Not used in under 5s

23

Streptomycin and capreomycin are both amino glycosides. They are ___ line anti TB drugs

Second line

24

Cycloserine, Ciprofloxacin and azithromycin are examples of?

Second line anti TB drugs

25

What would be a treatment regimen for active TB (ripe)?

Rifampicin and isoniazid for 6-9 months
Pyrazinamide for 2 months plus ethambutol

26

What would be a treatment regimen for latent TB?

Treat with immuno suppressants
Rifampicin for 6 months
Or rifampicin and isoniazid for 3 months

27

Why do we need a long duration of therapy for treating TB?

Bacteria in macrophages and Tubercules: hard for drug to penetrate
Rupturing of lesions: renewed infection
Drugs are only bactericidal against actively growing organisms, not dormant ones

28

What does MDR-TB mean?

Moderate drug resistance in TB
Strains are resistant to 2 or more first line drugs

29

What does XDR-TB stand for?

Extreme drug resistance in TB
Strains are resistant to 2 or more first line drugs
AND 3 or more second line drugs!!

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