L9 - chronic respiratory infections

Question 1

Tb slow growing

Answer 1

Generation time is 15-20 hours compared to normal bacteria 30mins-1hour

Question 2

Spread of TB

Answer 2

Through aerosol from infected individuals lung to another lung through spotting, sneezing, plates, etc

Question 3

Smear positive

Answer 3

27-50% of household contacts become infected

Question 4

Smear negative

Answer 4

<5%

Question 5

TB immunology

Answer 5

Mycobacteria are pahgocytosed by macrophages and trafficked to a pahgolysosome, which the host aims to kill through microbicidal molecules and acidification
Digestion and degradation by processes results in generation of antigens for T cell presentation

Question 6

Mycobacteria and phagolysosomes

Answer 6

MTb adapted to intracellular environment and aim to withstand phagolysosomal killing and escape to the cytosol

Question 7

MTb and CD4

Answer 7

CD4 T cells generate interferon gamma and this helps activate intracellular killing by macrophages
This can be successful or fails, but in most there is partial success

Question 8

Partial success in effective immunity against MTb

Answer 8

MTb don’t die they are kept inactive within a granuloma

Question 9

Pulmonary tb infection only

Answer 9

Bacilli Seattle in lung
Macrophages and lymphocytes seal in and contain and kill majority of infecting bacilli
Majority of people Mount an effective immune response that encapsulates and contains organisms forever

Question 10

In pulmonary Tb over ?% do not have any disease

Answer 10

95%

Question 11

Granulomas

Answer 11

Lesions that arise in a response that tries to contain mycobacteria

Question 12

Highly stimulated macrophages become…

Answer 12

Epithelial cells

Question 13

Langhans giant cells

Answer 13

Giant multinucleated cells formed through macrophages fusing

Question 14

Granuloma immunology

Answer 14

T cells infiltrate the mycobacteria lesions
Fibroblasts laid down around granuloma ‘wall off’
Central tissu may necrose and form a causeating granuloma

Question 15

Pulmonary Tb stats

Answer 15

2-5 develop clinically evident primary pulmonary disease

Question 16

Macrophages and pulmonary Tb

Answer 16

Macrophages phagocytise bacilli but fail to kill them
Bacilli containing macrophages drain into mediastinal lymph nodes which enlarge as they engage the T cell response
T cells activate which macrophages coalesce to form a granuloma
Granuloma grows and develops into a cavity

Question 17

Cavity

Answer 17

More likely in apex of lungs as there is more air and less blood supply or immune cells
Cavity is full of TB bacilli whc h are excelled when patients cough
Bacilli taken in lymphatic to the hilar lymph nodes