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CR2 > 30 - Tuberculosis > Flashcards

30 - Tuberculosis Flashcards

1
Q

What is the most common mycobacteria that causes TB

A

M.tuberculosis

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2
Q

What are other mycobacteria that cause TB

A

M. bovis
M. africanum
M. microti
M. canetti

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3
Q

Name a mycobacteria that doesn’t cause TB

A

M.avium complex

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4
Q

How is TB spread

A

In the air via droplet nuclei

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5
Q

What does the probability that TB will be transmitted depend on

A

Infectiousness of person with TB
Environment in which exposure occurred
Length of exposure
Strength of the tubercule bacilli

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6
Q

What is the best way to stop transmission of TB

A

Isolate infectious persons

Treatment to infectious persons as soon as possible

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7
Q

How can you diagnose a latent TB infection

A

Mantoux with PPD or gamma interferon release assays

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8
Q

What year did TB control programs begin in

A

1992

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9
Q

What year was Streptomycin, Isoniazid an PAS DISCOVERED

A

o Streptomycin in 1943

o Isoniazid and PAS – 1943 and 1952

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10
Q

What is the treatment for drug sensitive TB

A
  • Isoniazid, Rifampicin, Pyrazinamide + Ethambutol for 2 months
  • Rifampicin and Isoniazid for 4 months
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11
Q

What does it mean if the TB is multi-drug resistant

A

Resistant to INH, RIF plus amikacin,kanamycin or capreomycin (injectable!agents) and resistance to any fluroquinolone

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12
Q

Features of mycobacterium

A

Slow growing
Prefer o2 rich env
Live inside cells

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13
Q

Clinical features TB

A 
Fever
Night sweats
Weight loss
Chronic cough 
chest pain
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14
Q

Why is TB hard to treat

A

1) Lipid rich cell wall - difficult for AB to enter cell
2) Slow growing and hide in macrophages
3) Resistant to penicillin
4) Not gram neg or gram positive cell wall

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15
Q

What occurs in primary TB

A

Mycobacteria –> in middle lung
Acute inflammatory response from neutrophils
Neutrophils –> phagocytose bacteria abut cannot destroy
Nearby cells and neutrophils die (caseous necrosis)
Some bacteria die

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16
Q

What is the ghon focus

A

Aggregation of macrophages around a necrotic centre

17
Q

What type of immune response in primary tb

A

Type IV hypersensitivity

18
Q

Structure of the caseous tissue

A 
Caseous necrosis around
macrophages around that (ghon focus)
fused macrophages - langhan cells
lymphocytes around the macrophages
fibroblasts on the outside
19
Q

What occurs in healthy individuals with primary tb

A

Ghon focus heals with deposits of collagen from fibroblasts

Ca salts are deposited in the collagen –> Ghon complex (ca on xray)

20
Q

Secondary TB

A

o Bacteria remain alive in Ghon complex, immunosuppression/malnourishment –> bacteria escape and symptoms appear- REACTIVATION

21
Q

How to diagnose TB

A 
PCR
Mantoux
CXR
Histology 
Sputum
22
Q

Mantoux test pos in =

A

 15mm or more = positive in healthy
 10-15mm= positive in med risk ( drug users, homeless)
 5-9mm= positive in HIV

23
Q

Chest X-ray features

A

bilateral opacities, cavitations, calcification, hilar shadowing

24
Q

Histology

A

caseous granulomas with Langerhans giant cells on h and E stain

25
Q

Microbiology

A

Lowenstein Jensen medium – 4/6wks and sensitivity) + STAINING zielh neilson (red) or more sensitive auramine stain (Orange under fluorescent microscope) reveals AFB** inside macrophages

26
Q

Pyrazinamide

A

inhibits the enzyme fatty acid synthase (FAS) which is required by the TB bacterium to synthesise fatty acids.
SE - gout

27
Q

Ethambutol

A

bacteriostatic, It prevents the formation of the cell wall

SE - vision changes

28
Q

Rifampicin

A

antibiotic which inhibits bacterial DNA-dependent RNA polymerase
SE =- Red-orange metabolites + induces liver enzymes

29
Q

Isoniazid

A

prevents synthesis of mycolic acid, component of the TB bacterial cell wall.
SE - Neuropathy, hepatitis

CR2 (34 decks)

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