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Respiratory System > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

What organism causes tuberculosis

A

Mycobacterium tuberculosis complex bacteria

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2
Q

What organism most commonly causes TB?

A

Mycobacterium tuberculosis

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3
Q

Describe the pathogenesis of TB

A
  • aerosols inhaled
  • engulfed by alveolar macrophages
  • at this point most have a spontaneous recovery
  • those who don’t > primary TB (latent or disseminated)
  • if latent, TB can reactive causing post primary TB
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4
Q

Describe the mycobacterium tuberculosis

A
  • non motile bacilli
  • obligate aerobe
  • long chain fatty acids + glycolipids in cell wall
  • slow growing
  • acid fast bacilli
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5
Q

Risk factors of TB

A
  • Close contact with patient infected with pulmonary TB
  • high prevalence in India + sub-Sahara Africa
  • extremes of age
  • homelessness
  • diabetes
  • immunosuprresion e.g. HIV
  • alcohol or drug dependence
  • prolonged steroid use
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6
Q

Risk factors for reactivation of TB

A
  • infection with HIV
  • substance abuse
  • prolonged therapy with corticosteroids
  • organ transplant
  • diabetes mellitus
  • low body weight
  • severe kidney disease
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7
Q

Why can gram stain not be used for mycobacterium tuberculosis?
What is used instead?

A

Gram satin cant go through thick fatty acid cell wall
ZN staining

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8
Q

What are the three types of TB disease?

A

Pulmonary TB
Extrapulomary TB
Miliary TB

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9
Q

Site of miliary TB

A

Carried to all parts of the body through bloodstream

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10
Q

Who is extrapulmonary TB often found in?

A

HIV infected
Immunosuppressed
Young children

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11
Q

Symptoms of pulmonary TB

A
  • fever
  • night sweats
  • weight loss/anorexia
  • fatigue
  • cough
  • haemoptysis
  • malaise
  • breathlessness if pleural effusion
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12
Q

Signs of pulmonary TB on examination

A
  • often no chest signs despite CXR abnormalities
  • crackles in affected area
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13
Q

Extrapulmonary presentation of TB

A
  • erythema nodosum
  • meningitis
  • lymphadenopathy
  • pericardial effusion
  • cold abscess
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14
Q

What is a cold abscess in TB?

A

a firm painless abscess, often in the neck

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15
Q

Investigation of pulmonary TB

A
  • CXR
  • consider CT chest if CXR not typical
  • histology
  • if productive cough, 3x ZN stain + TB culture
  • Mantoux test
  • Interferon-gamma release assay
  • NAAT
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16
Q

How does a TB infection appear on CXR?

A
  • often at apex
  • ill defined patchy consolidation
  • cavitation within consolidation
  • healing results in fibrosis
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17
Q

What is a ghon focus?
How does it form?

A
  • spherical granuloma with central caseation, caused by the macrophages ingesting Mycobacterium tuberculosis
  • three weeks after infection, immune cells surround site of infection > granuloma
  • this isolates bacteria to prevent spreading
  • tissue inside granuloma dies > caseous necrosis
  • the necrotic area is a ghon focus
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18
Q

What is a ghon complex?

A
  • to infection spread to hilar lymph nodes
  • the caseating tissue (ghon focus) + associated lymph node is the ghon complex
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19
Q

What can be done if a suspected TB patient isn’t producing enough sputum for culture?

A
  • sputum induction with nebulised hypertonic saline
  • bronchoscopy + bronchoalveolar lavage
20
Q

Diagnosis of TB

A

sputum/blood cultures (gold standard) but can take months so nucleic acid amplification tests done as it is faster

21
Q

Outline nucleic acid amplification tests

A
  • assess for genetic material of pathogen
  • performed on sputum sample
  • provides info about bacteria faster than a culture
22
Q

What is NAAT used for?

A

diagnosing TB in patients with HIV or under 16

23
Q

Diagnosing latent TB

A

Mantoux test (tuberculin skin test)
Interferon Gamma Release Assay

24
Q

Outline the Mantoux Test

A
  • injecting tuberculin into the intradermal space on the forearm
  • infection creates a bleb under the skin
  • the bleb is measured after 72 hours
  • > 5mm is positive
25
Q

Outline interferon-gamma release assays

A
  • mixing a blood sample with M.tuberculosis antigens
  • if there is a previous infection, WBCs will release interferon-gamma
  • positive result if interferon-gamma is released
26
Q

Where is TB common?

A

Africa
Asia
Latin America

27
Q

How does post primary TB arise?

A

Reactivation of latent infection

28
Q

What does primary TB lead to?

A
  • asymptomatic latent TB (more common)
  • primary progressive pulmonary/extrapulmonary TB through dissemination
29
Q

Main sites of extrapulmonary TB

A
  • CNS
  • pleura
  • bones + joints
  • urogenital tract
30
Q

What is miliary TB?

A

Form of TB characterised by widespread dissemination to extrapulmonary organ causing tiny lesions

31
Q

What is suggestive of miliary TB on chest x ray?

A

Many tiny spots throughout lung field

32
Q

What do all patients with miliary TB need + why?

A

CT/MRI head +/- LP
to exclude CNS involvement e.g. TB meningitis/CNS TB

33
Q

Lumbar puncture results of TB meningitis/CNS TB

A

high protein
low glucose
lymphocytosis

34
Q

What vaccination is given to prevent TB?
Describe it
What must be done before the vaccine?

A
  • BCG vaccine
  • intradermal injection of live attenuated mycobacterium bovis > creates immune response + immunity to M.tuberculosis
  • tested with Mantoux test, risk of immunosuppression + HIV
35
Q

Who is the TB vaccine given to?

A
  • those at increased risk of TB
  • healthcare workers
36
Q

Treatment of latent tuberculosis

A

isoniazid + rifampicin for 3 months
OR
isoniazid for 6 months

37
Q

First line medication for active TB
How long must each be taken for?

A

Rifampicin: 6 months
Isoniazid: 6 months
Pyrazinamide: 2 months
Ethambutol: 2 months
.
take all for 2 months and then continue for 4 months with just rifampicin + isoniazid

38
Q

Management of TB

A
  • notify public health England
  • admit to negative pressure side room + start infection control measures
  • routine bloods (especially LFTs)
  • HIV test
  • screening + tracing of close contacts
  • medications: isoniazid, rifampicin, pyrazinamide + ethambutol
39
Q

Due to certain side effects of TB drugs, what must be done before and during treatment?

A
  • risk of hepatitis + visual disturbances
  • baseline LFTs + visual acuity tests
  • monitor both whilst on treatment
40
Q

Side effects of TB drugs

A
  • hepatitis: rifampicin, isoniazid, pyrazinamide
  • visual disturbance: ethambutol
  • peripheral neuropathy: isoniazid
  • orange secretions: rifampicin
41
Q

Side effects of rifampicin

A

Orange urine/secretions
Hepatitis
Thrombocytopaenic rash

42
Q

side effects of isoniazid

A
  • hepatitis
  • rashes
  • peripheral neuropathy
  • psychosis
43
Q

Side effects of pyrazinamide

A
  • hepatitis
  • rashes
  • vomiting
  • arthralgia
44
Q

Side effects of ethambutol

A

visual disturbances

45
Q

What must always be given with isoniazid?
Why?

A

pyridoxine (vit B6)
Avoid damage to peripheral nerves

46
Q

What skin findings can arise with TB?

A

Erythema nodosum

47
Q

Pulmonary complication for TB

A
  • pleurisy
  • plural effusion
  • empyema
  • pneumothorax
  • bronchiectasis
  • respiratory failure

Respiratory System (25 decks)

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