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Module 2 > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

What causes TB

A

Infection with Mycobacterium tuberculosis, M.bovis

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2
Q

What is mycobacterium tuberculosis

A

Obligate aerobe
rod shaped bacteria spread via air-born droplets and dust micro particles
acid fast
slow rate of growth
sensitive to heat and UV radiation
non-motile

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3
Q

What is pulmonary and extrapulmonary TB

A

pulmonary - lungs
extrapulmonary - other body parts

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4
Q

Where is the TB situation the worst

A

Africa
half of all HIV infected adults infected with M.tuberculosis

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5
Q

What are the less frequent causes of TB

A

M.bovis
M.africanum

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6
Q

What is used in the BCG vaccine

A

attenuated M.bovis

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7
Q

Why has TB not been eradicted

A

 Global burden
 Laten TB infection
 Drug resistance
 Social determinants of health
 Co-infection with HIV
 Diagnostic challenges
 Stigma and lack of awareness
 Inadequate healthcare infrastructure
 Migration

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8
Q

Who are at high risk of TB

A

-recent TB infection
-weakened immune system

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9
Q

Risk factors for TB

A

 Low socio-economic status
 Diseases that weaken the immune system like HIV, cancer
 Person on immunosuppressant like steroids
 Migration from a country with high cases like West Africa
 Malnutrition
 Crowded living conditions
 Substance abuse like alcohol and drug abuse
 Healthcare workers
 Smoking, exposure to silica dust
 Medications like TNF and cancer drugs

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10
Q

Latent TB infection

A

-no signs or symptoms
-host defences prevent growth of bacteria (macrophages engulf bacteria)
-not infectious
-skin or blood test positive
-normal chest x-ray

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11
Q

TB disease

A

-primary infection
-signs and symptoms present
-spread infection
-skin or blood test positive
-abnormal chest x ray or sputum sample

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12
Q

Methods of TB diagnosis

A

-Tuberculin skin test (TST)/Mantoux
-Inferon-Gamma Release Assay (IGRA)
-Chest X ray
-Sputum smear microscopy
-Molecular testing (PCR/Nucleic Acid Amplification Test (NAAT)
-CT scan
-Bronchoscopy and thoracenthesis
-Biopsy

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13
Q

What is the Tuberculin Skin Test (TST)

A

Inject 0.1ml of purified protein derivatives (PPD) under the forearm
measures induration (raised area)
positive test = 5mm or larger
does not differentiate between latent and active TB

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14
Q

What are the limitations of the Mantoux test

A

false positive results due to prior BCG vaccine and exposure to non-tuberculosis bacteria (atypical mycobacteria)
false negative due to weakened immune system/malnutrition and viral infection

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15
Q

TST results

A

> 5mm (HIV positive/recent TB/organ transplant)
10mm (recent arrivals from high prevelance countries/IV drug users)
15mm (no known risk factors)

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16
Q

Interferon gamma release assay

A

detect release of IFN-gamma
preferred to TST (quantitative)
blood drawn contains antigens associated with M. tuberculosis
amount of IFN gamma released by stimulated WBCs measured
T lymphocytes release gamma interferon

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17
Q

What does a chest x ray reveal

A

 Infiltrates (areas of increased density)
 Nodules
 Cavities
 Consolidations (areas of lung tissue filled with fluid or
cellular material)
 Lymph node enlargement: visible on the X-ray as round or
oval-shaped densities
 Pleural effusion: seen as a hazy area or blunting of the
normally sharp angle between the lung and chest wall

18
Q

Sputum smear microscopy

A

detects acid-fast bacilli (AFB)
sputum to create thin smear
stained using Ziehl-Neelsen

Bright red rods against blue/dark background

19
Q

PCR and NAAT

A

PCR amplifies specific component of DNA NAAT (amplifies D)
diagnoses specific Mycobacterium
very expensive
NICE - request if suspicion of pulmonary TB/HIV/need for large contact tracing

20
Q

Symptoms of TB

A

 A persistent cough
 Constant fatigue
 Weight loss
 Loss of appetite
 Fever
 Coughing up blood
 Night sweats

21
Q

primary stage of TB

A

asymptomatic/ mild flu like symptoms

22
Q

reactivated TB

A

takes months to appear
gradual onset of anorexia, weight loss, fever, night sweats

23
Q

TB affecting the lung

A

Persistent cough lasting longer than 3 weeks. Sputum (mucoid
then purulent); containing bacilli if cavitation occurs, haemoptysis

24
Q

Systemic TB

A

headache and neurological deficit in brain metastasis, swelling in neck if lymph involvement

25
Q

What is Granulomatous inflammation

A

type of chronic inflammation
granulomas are compact aggregates of immune cells
contain macrophages, epitheloid cells (activated macrophages), lymphocytes
macrophages engulf stimuli but may not destroy it completely

26
Q

What happens to the center of the granuloma

A

undergoes necrosis forming a caseous core

In TB ONLY: caseous necrosis; yellow-white cheese-like (gross)
amorphous granular lysed cells with no cell outlines/architecture

27
Q

What occurs in persistent activation and stimulation by the antigen

A

macrophages tranform into epitheloid cells

28
Q

How is TB transmitted

A

-airbourne mucus droplet nuclei
-cough
-small droplets or aerosols reach alveoli
-rarely via direct contact
-Waxy outer coating makes organism resistant to desiccation

29
Q

What is the pathogenesis of TB

A

bacteria reach the alveoli and are phagocytosed by macrophages (>70% asymptomatic)

30
Q

Pathogenesis of immunocompromised state

A

reactivation of the infection, bacterial escapes from granuloma and
multiplie like in HIV, young and elderly leading to the active disease
can affect other body parts

31
Q

What is the Ghon focus

A

 Primary lesion of granulomatous inflammation
 Usually subpleural (lower lobes)
 Composed of macrophages and other immune cells

32
Q

What is the ghon complex (primary complex)

A

A Ghon focus & infection of adjacent lymphatics and hilar lymph nodes
When a Ghon’s complex undergoes fibrosis and calcification it is called a
Ranke complex

33
Q

How long does it take for the primary complex/ghon complex to ressolve

A

weeks or months
leaves signs of fibrosis and calcification detectable on a chest x-ray

34
Q

Why is TB with cavitation formed

A

bacterial infects and damage the tissues leading to empty spaces or cavities
-caseous necrosis creating a liquifiable centre leading to cavities (cheese like)
-serve as bacteria reservoir which is released when patient coughs/sneezes

35
Q

how does TB spread in the body

A

blood or lymphatic system

36
Q

what does TB spread in the body cause

A

-meningitis in CNS
-joint pain
-pott’s disease in the spinal cord
-urinary symptoms in kidneys
-infertility
-lymphadenitis
-pericarditis
-GIT ulcers
-skin lesions and ulcers

37
Q

What is miliary TB

A

2mm spots
life threatening illness
seeds expand, coalesce, destroy large areas of organs

38
Q

usual secondary TB (TB with AIDS)

A

CD4 count >300cell/ml

39
Q

primary progressive TB (TB with AIDS)

A

CD4 count>200cell/ml

40
Q

TB and HIV co-infection

A

15% of world wide deaths from TB were co-infected with HIV

Module 2 (7 decks)

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