L9 - chronic respiratory infections

Question 1

TB microbiology

Answer 1

aerobic, non-spore-forming, non-motile bacillus

Question 2

TB slow growing

Answer 2

generation time is 15-20 hours compared to most bacteria having 30mins-1hours

Question 3

How is TNB spread

Answer 3

in aerosol from an infected individual’s lung to another lung via spitting, sneezing, plates, etc

Question 4

Smear positive

Answer 4

17-50% of household contacts becoming infected

Question 5

Smear negative

Answer 5

<5%

Question 6

TB immunology

Answer 6

Mycobacteria are phagocytose by macrophages and trafficked to a phagolysososme, which the host aims to kill through microbicidal molecules and acidification
Digestion and degradation by proteases results in generation of antigens for presentation to T cells

Question 7

Mtb and phagolysosomes

Answer 7

MTb has adapted to the intracellular environment and aims to withstand the phagolysosomal killing and escapes to the cytosol

Question 8

Mtb and effective immunity

Answer 8

requires CD4 T cells which generate interferon gamma and this helps activate intracellular killing by macrophages, this can be successful or fail but is mostly partial success

Question 9

Effective immunity partial success

Answer 9

where the MTb don’t die but are kept inactive within a granuloma

Question 10

Pulmonary TB infection only

Answer 10

Bacilli settle in lung and are sealed in by macrophages and lymphocytes, containing and killing the majority of infecting bacilli

Question 11

Pulmonary TB infection in people

Answer 11

majority of people mount an effective immune response that encapsulates and contains the organism forever
>95% do not have any disease

Question 12

Granulomas

Answer 12

lesions that arise in a response that tries to contain mcobacteria

Question 13

Langhans giant cells

Answer 13

giant multinucleate cells formed when some macrophages fuse together

Question 14

Highly stimulated macrophages become…

Answer 14

epithelial cells

Question 15

T cells and TB

Answer 15

T cells infiltrate the Mtb lesions, fibroblasts laid down around granuloma ‘wall off’
the central tissue may necroses and form a ‘nauseating’ granuloma

Question 16

Pulmonary TB

Answer 16

2-5 develop clinically evident primary pulmonary disease

Question 17

Phagocytosis of pulmonary TB

Answer 17

macrophages phagocytose bacilli but fail to kill them
bacilli contained macrophages drain to mediastinal lymph nodes which enlarge as they engage the T cell response
T cells activate which macrophages coalesce to form a granuloma

Question 18

Granuloma formation most likely to occur in…

Answer 18

the lung apex as there is more air and less blood supply/immune cells

Question 19

cavity formation

Answer 19

granulomas grow to form a cavity, which is full of TB bacilli which are expelled when a patient coughs
bacilli taken in lymphatics to hilarious lymph nodes

Question 20

Gram staining acid fast bacilli Mtb

Answer 20

high lipid content with mycelia acids in cell walls make it resistant to staining
slightly curved, beaded bacilli, v forms

Question 21

Slow growth in culture

Answer 21

means need decontamination steps to kill off other rapid-growing bacteria

Question 22

Solid culture L. J. Sple

Answer 22

egg-based Lowenstein Jensen, agar-based, from microscopy positive material 2-4 weeks and from microscopy negative material 4-8 weeks

Question 23

Liquid culture MGIT

Answer 23

1-3 weeks and automated systems

Question 24

Nucleic acid detection

Answer 24

amplification using PCR, purifies and concentrates MTb, sonicates to release genomic material then performs PCR
rapid MTb result and detects Rifampicin resistance using fluorescence
used for TB endemicc countries

Question 25

Haematogenous dissemination

Answer 25

occurs if TB is not contained and leads to serious non-pulmonary disease
this may happen after primary infection or after reactivation

Question 26

TB settling in lung apex

Answer 26

can be taken into hilarious lymph nodes to result in genito-urinary TB
can also enter lung resulting in TB meningitis, military TB and pleural TB

Question 27

Lifetime TB risk

Answer 27

10% risk then 0.1% per year after first year

Question 28

TB reactivation risks

Answer 28

age, malnutrition, intensity of exposure, immunosuppression

Question 29

Nocardiosis infection

Answer 29

bacteria found in the environment, i.e. standing water, decaying plants and soils
slow onset and prolonged
breathe in dust continuing bacteria or when a hospitalised patient is infected from contaminated medical equipment

Question 30

nocardiosis symptoms

Answer 30

fever, weight loss, night sweats, coughing and chest pain

Question 31

Nocardiosis spread

Answer 31

can form granulomata in lungs and associated lymph nodes, can spread to other parts of the body e.g. brain abscess

Question 32

Meliodosis bacteria

Answer 32

Burkholderia pseudomallei

Question 33

Meliodosis infection

Answer 33

in tropical climates found in contaminated water and soil, spread through direct contact with the contaminated source

Question 34

Meliodois staining

Answer 34

gram negative rods

Question 35

Meliodosis symptoms

Answer 35

2-4 weeks development, cough and chest pain, high fever, headache, anorexia and weight loss
pneumonia and lung abscesses
metastatic infection and skin disease

Question 36

Non-tuberculosis mycobacteria

Answer 36

Mycobacteria that live in the environment in soil or water

Question 37

Non-tuberculosis mycobacteria symptoms

Answer 37

slow development of chronic cough, coughing up blood, shortness of breath, fatigue, low-grade fever, night sweats and weight loss

Question 38

Pulmonary hitsplasmosis

Answer 38

dimorphic fungus found worldwide, slower onset pneumonia with visible intrathoracic lymph, pulmonary nodule and cavitary lung disease, granulomata on bopsy

Question 39

Pulmonary histoplasmosis infection

Answer 39

results in progressive loss of pulmonary function in most patients and death in up to 30% of cases