Mycobacteria

Question 1

what bacterium causes leprosy

Answer 1

Mycobcteroum Leprae

Question 2

what are the cardinal features or leprosy

Answer 2

skin lesions

Thickened peripheral nerves

Acid-fast bacilli on smears or biopsy

Question 3

what type of bacterium are mycobacterium

a)Gram +ve
b)Gram -ve
c) Acid fast +ve

Answer 3

C
Is evolutionarily gram +ve but doesn’t stain +ve. Is positive with the ziehle neelson stain

Question 4

what is the shape of mycobacteria

Answer 4

Rod (bacilli)

Question 5

How much bacteria do you need to diagnose TB via acid fast staining

Answer 5

10,000 per ml of sputum

Question 6

Mycobacteria tend to be

A) Aerobic
B) Anaerobic

Answer 6

aerobic

Question 7

Mycobacteria are motile

T/F

Answer 7

F

Question 8

Briefly describe the cell wall of mycobacteria

Answer 8

High molecular weight lipids
-Mycolic acids + lipoarabinomannan

Question 9

Mycobacterium is slow growing
T/F

Answer 9

T

Question 10

Mycobacterium can survive inside macrophages
T/F

Answer 10

T

Question 11

What are the challenges to treating mycobacterium (not medication)

Answer 11

Slow growing
Slow reproduction
Slow growth in culture
Slow response to treatment (6mnths minimum)

Question 12

State four examples of disease caused by mycobacteria

Answer 12

Leprosy, M.leprae
Buruli Ucler, M.ulcerans
Fish tank granuloma, M. marinum
Tuberculosis, M.tuberculosis

Question 13

Describe the classification of mycobacteria, e.g. intracellular or can grow on artificial media etc.

Answer 13

can grow on artificial media –> cell walled –> single celled –> rods

Question 14

Describe the structure of mycobacteria and what is used to stain it.

Answer 14

Aerobic, slightly curved, beaded, non-motile bacilli with high molecular weight lipids in the cell wall

Ziehl-Neelson stain (contains carbol fuchsin, acid alcohol and methylene blue)

Question 15

Describe the causes of TB, and factors that make it harder to treat, how is it transmitted?

Answer 15

Caused by Mycobacterium tuberculosis

Thick lipid-rich cell wall makes immune cell killing + penetration of drugs challenging

Slow growth with gradual onset of disease –> takes longer to diagnose + treat

Aerosol transmission

Question 16

Describe primary tuberculosis

Answer 16

Initial contact by alveolar macrophages

Bacilli taken in lymphatics to hilar lymph nodes

Question 17

Decsribe latent tuberculosis

Answer 17

Cell mediated response from T cells

Primary infection contained but cell mediated immune (CMI) response persists

There is no clinical disease, but is detectable CMI to TB on the tuberculin skin test

Question 18

Describe Pulmonary tuberculosis

Answer 18

Granulomas form around bacilli that have settled in apex (where there is ++ air, - blood supply –> less white cells to fight infection)

TB may spread in lung, causing other lesions

Can occur immediately after primary infection, or a month later after reactivation

Question 19

What are the constituents of the tuberculosis primary complex?

Answer 19

lymphatics
Lymph nodes
Granulomas

Question 20

Describe where TB could spread to beyond the lungs

Answer 20

Bacilli in lung + lymph nodes could spread to:
Genito urinary system to genitourinary TB

Pleural TB
Miliary TB
Bone and joint TB

Question 21

What is the consequence of TB in the spine?

Answer 21

Gibbus formation

Question 22

Describe the immune response to mycobacteria

Answer 22

Mycobacteria are phagocytosed by macrophages + traffic to phagolysosomes

The bacterium has adapted to the intracellular environment and aims to withstand phagolysosomal killing, to escape to cytosol

Effective immunity requires CD4 T cells to generate interferon-gamma –> activate intracellular killing by macrophages

Question 23

What are the two consequances of granuloma formation?

Answer 23

Granuloma is effective –> mycobacteria shut down
metabolically –> dormancy

Granuloma fails –> formation of a cavity full of live
mycobacteria –> disseminated disease (consumption)

Question 24

what is a granuloma made of

Answer 24

Macrophages and Th1 capable of synthesysing interferon gamma, and other cytokines, e.g. TNFa

Question 25

What is the standard and second line therapy in Anti-TB drugs?

Answer 25

Standard therapy - INH, RIF, PZA and ETH x 2 months, followed by INH and RIF for further 4 months

Second line - injectable agents, e.g. streptomycin, cycloserine, capreomycin

Question 26

Which strain of TB is multi drug resistant? How is it treated?

Answer 26

XDR-TB, resistant to four commonly used TB drugs
With BPal Regimen:
Bedaquiline, Pretomanid, Linezolid
all for 6 months