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Year One - Respiratory System > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

What is tuberculosis (TB)?

A

It is defined as a granulomatous infectious disease caused by the mycobacterium tuberculosis bacteria

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2
Q

TB is a multi-system disease, which organ does it primarily affect?

A

Lungs

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3
Q

What are the three bacteria in the mycobacterium tuberculosis complex?

A

M. tuberculosis

M. bovis

M. africanum

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4
Q

What is the most common bacteria to cause TB?

A

M. tuberculosis

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5
Q

What are the three characteristic features of mycobacterium tuberculosis?

A

Bacillus shaped

Gram-positive

Aerobic in nature

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6
Q

What are the three classifications of TB?

A

Primary Tuberculosis

Secondary Tuberculosis

Miliary Tuberculosis

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7
Q

What is primary TB?

A

It is defined as the initial exposure to mycobacterium tuberculosis in a non-immune host

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8
Q

How is TB transmitted?

A

Droplet inhalation

Therefore commonly spread through coughing and sneezing

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9
Q

Describe the pathophysiology of TB following exposure

A

There is activation of the immune system, which results in the migration of macrophages to the lungs

These macrophages engulf the mycobacterium and then migrate to regional hilar lymph nodes

There is then granuloma formation, with central caseating necrosis, within the lung and regional lymph nodes

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10
Q

What hypersensitivity reaction mediates the inflammatory response associated with TB?

A

Type 4

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11
Q

What is the Ghon focus?

A

It is the term used to refer to the tubercle-laden macrophage lesions within the lung

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12
Q

What is the Ghon complex?

A

It is the term used to refer to the collective tubercle-laden macrophage lesions within the lung and regional lymph nodes

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13
Q

What are the three subclassifications of primary TB?

A

Cleared Primary Tuberculosis

Latent Primary Tuberculosis

Progressive Primary Tuberculosis

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14
Q

What is cleared primary TB?

A

It is defined as tuberculosis infection in which the mycobacterium are completely destroyed through the activation of macrophages

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15
Q

What is latent primary TB?

A

It is defined as tuberculosis infection in which the mycobacterium remain dormant within the lungs

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16
Q

What is another term for progressive primary TB?

A

Active TB

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17
Q

What is progressive primary TB?

A

It is defined as uncontrolled tuberculosis infection, in which the multiplication of bacteria occurs

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18
Q

What is another term for secondary TB?

A

Post-primary TB

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19
Q

What is secondary TB?

A

It is defined as reactivation of initial latent infection

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20
Q

What is miliary TB?

A

It is defined as a disseminated form of tuberculosis, in which infection is spread from one area of the body to other organ systems via haematogenous mechanisms

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21
Q

What are the six most common extrapulmonary sites of TB?

A

Central nervous system

Cervical lymph nodes

Vertebral bodies of the spine

Gastrointestinal system

Genitourinary system

Pleural structures

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22
Q

How does TB affect the CNS?

A

Meningitis

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23
Q

How does TB affect the cervical lymph nodes?

A

Scrofula

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24
Q

How does TB affect the pleural structures?

A

Pleurisy

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25
Q

How does TB affect the pleural vertebral bodies of the spine?

A

Pott’s disease

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26
Q

What are the six risk factors of TB?

A

Tuberculosis Infection Close Contact

Immigration From High Prevalence Areas

Immunosuppression

Homelessness

Intravenous Drug Users

Alcoholism

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27
Q

What are the two main countries with high TB prevalence?

A

India

Sub-Saharan Africa

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28
Q

What are three immunosuppression conditions associated with TB?

A

HIV

Malignancy

Steroids

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29
Q

What are the nine clinical features associated with TB?

A

Fever > 38°C

Weight Loss

Lymphadenopathy

Chronic Productive Cough

Haemoptysis

Dyspnoea

Pleuritic Chest Pain

Bronchial Breathing

Percussion Dullness

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30
Q

What rash is asssociated with tuberculosis?

A

Erythema Nodosum

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31
Q

What additional clinical features may be associated with TB?

A

In cases of extra-pulmonary disease, individuals will present with additional clinical features relevant to the organ system affected

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32
Q

What are the clinical features seen in primary TB?

A

These patients are usually asymptomatic, or present with a fever only

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33
Q

What six investigations are used to diagnose TB?

A

Mantoux Test

Interferon-Gamma Release Assays (IGRAs)

Microscopy

Chest X-Ray (CXR)

Sputum Culture

Nucleic Acid Amplification Test (NAAT)

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34
Q

When is the Mantoux test used?

A

It is used to identify a previous immune response to tuberculosis – which can be related to previous vaccination, latent tuberculosis or active tuberculosis infection

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35
Q

What is the Mantoux test?

A

It involves the injection of PPD tuberculin into the intradermal space on the forearm

This results in the formation of a bleb under the skin following a 72 hour period

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36
Q

What is PDD tuberculin?

A

It is a collection of tuberculosis proteins that have been isolated from the bacteria

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37
Q

What induration diameter defines a negative Mantoux test?

A

< 6mm

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38
Q

What are two causes for a false negative Mantoux test?

A

Long Term Steroid Administration

Sarcoidosis

39
Q

What induration diameter defines a positive Mantoux test?

A

6mm - 15mm

40
Q

What induration diameter defines a strongly positive Mantoux test?

A

> 15mm

41
Q

What should be conducted following a positive Mantoux test result?

A

There should be further investigations to assess for active disease

42
Q

When is IGRA used?

A

It is used to identify a previous immune response to tuberculosis – which can be related to previous vaccination and latent tuberculosis infection

An IGRA test cannot be used to confirm the presence of active tuberculosis infection, unlike the Mantoux test

43
Q

What is an IGRA?

A

It involves collecting a blood sample and mixing it with antigens from the tuberculosis bacteria

44
Q

What is defined as a positive IGRA result? Explain the pathophysiology of this result

A

The release of interferon-gamma

This is due to the sensitisation of WBCs to those antigens during a previous immune response

45
Q

How does TB appear on gram stained microscopy?

A

Gram stained microscopy is deemed ineffective due to the bacteria’s resistance to acids used in the staining procedure

This is termed as acid-fastness, and therefore tuberculosis bacteria are described as acid-fast bacilli (AFB)

46
Q

What is important to note about the gram staining of TB?

A

All mycobacteria will stain positive for an AFB smear

This result is therefore not specific for tuberculosis

47
Q

How does TB appear on Ziehl-Neelsen stained microscopy?

A

The bacilli appear bright red against a blue background

48
Q

What are the three features of primary TB on CXR?

A

Patchy consolidation

Pleural effusions

Hilar lymphadenopathy

49
Q

What is the feature of secondary TB on CXR?

A

Patchy/nodular consolidation with cavitation in the upper lung zones

50
Q

What is cavitation?

A

It is defined as gas filled spaces in the lungs

51
Q

What is the feature of miliary TB on CXR?

A

‘Millet seeds’ uniformly distributed throughout the lung fields

52
Q

What is the gold standard investigation used to diagnose TB?

A

Sputum culture

53
Q

How is sputum culture used to diagnose TB?

A

It is used to enable bacterial culture to be performed and therefore assess drug sensitivities

54
Q

How many sputum culture samples are required to test for TB?

A

Three

One has to be in the morning

55
Q

What two techniques can be used to produce sputum if individuals are struggling?

A

Hypertonic saline

Bronchoscopy with lavage

56
Q

How long does it take to receive sputum culture results?

A

1 - 3 weeks

57
Q

Do we wait for sputum culture results before starting treatment?

A

No

58
Q

In which patients is sputum culture first line for diagnosing TB?

A

HIV

59
Q

What is NAAT?

A

It checks directly for the DNA or RNA of a bacterial organism

60
Q

What bacteria sample is used to conduct NAAT in TB?

A

Sputum sample

61
Q

How quickly do we receive NAAT results?

A

24 - 48 hours

Therefore, faster than a traditional sputum culture

62
Q

When is NAAT used?

A

It is only used when this information would alter treatment or there is a high risk of complication development

63
Q

What are the four pharmacological options used in active TB?

A

RIPE

Rifampicin

Isoniazid

Pyrazinamide

Ethambutol

64
Q

What is the mechanism of action of rifampicin?

A

It inhibits bacterial DNA dependent RNA polymerase, preventing transcription of DNA into mRNA

65
Q

How long do we administer rifampicin for to treat active TB?

A

6 months

66
Q

What are the three side effects of rifampicin?

A

Orange Secretions (Urine/Tears)

P450 Liver Enzyme Inducer

Hepatitis

67
Q

What does P450 liver enzyme inducement mean?

A

There is a reduced effect of drugs that are metabolised by the liver (contraception pills*)

68
Q

How do we remember the key side effect of rifampicin?

A

Rifampicin = Red an orange pissin

69
Q

What is the mechanism of action of isoniazid?

A

It inhibits mycolic acid synthesis

70
Q

How long do we administer isoniazid for to treat active TB?

A

6 months

71
Q

What are the five side effects associated with isoniazid?

A

Peripheral Neuropathy

Hepatitis

Agranulocytosis

Liver Enzyme Inhibitor

Drug-Induced Lupus

72
Q

How do we prevent the isoniazid side effect of peripheral neuropathy?

A

We administer pyridoxine (vitamin B6)

73
Q

How do we remember the key side effect of isoniazid?

A

Isoniazide = im so numb acid

74
Q

Due to isoniazid inhibiting the P450 system, which drug should be monitored? Why?

A

Warfarin

This inhibition reduces the metabolism of warfarin, causing prolongation of its effects which increases INR

75
Q

What is the mechanism of action of pyrazinamide?

A

It is converted by pyrazinamidase into pyrazinoic acid, which inhibits fatty acid synthase I

76
Q

How long do we administer pyrazinamide for to treat active TB?

A

2 months

77
Q

What are the four side effects of pyrazinamide?

A

Gout

Hepatitis

Arthralgia

Myalgia

78
Q

What is the mechanism of action of ethambutol?

A

It inhibits the enzyme arabinosyl transferase, which polymerizes arabinose into arabinan

79
Q

How long do we administer ethambutol for to treat active TB?

A

2 months

80
Q

What are the three side effects of ethambutol?

A

Optic Neuritis

Reduced Visual Acuity

Colour Blindness

81
Q

How do we remember the key side effect of ethambutol?

A

Ethambutol = eye thambutol

82
Q

In active TB with CNS involvement, how do we adjust pharmacological management?

A

We administer isoniazid and rifampicin for twelve months instead of six months

83
Q

What are the four conservative management options for active TB?

A

Infectious disease testing

Public health notification

Contact tracing

Isolation

84
Q

What three infectious diseases do we screen for in TB patients?

A

HIV

Hepatitis B

Hepatitis C

85
Q

How long should TB patients isolate for?

A

Until they have been administered at least two weeks of pharmacological treatment

86
Q

In hospitals how do we prevent airborne spread of TB?

A

Negative pressure rooms

87
Q

How do we treat latent TB?

A

It doesn’t require treatment in individuals who are asymptomatic

We only treat individuals who are at high risk of re-activation

88
Q

How do we treat latent TB patients who are at high risk of re-activation?

A

Isoniazid and rifampicin for three months

OR

Isoniazid for six months

89
Q

What is the BCG vaccine?

A

It involves an intradermal injection of live attenuated tuberculosis

90
Q

What does attenuated mean?

A

Weakened

91
Q

Which individuals receive the BCG vaccine?

A

Those at high risk of TB

92
Q

What are the six high risk groups of TB?

A

Neonates Born In UK Areas With High TB Prevalence

Neonates With Relatives From Countries With High TB Prevalence

Neonates With TB Family History

Unvaccinated Individuals With TB Close Contact

Unvaccinated Individuals From Countries With High TB Prevalence

Healthcare Workers

93
Q

What investigation is conducted prior to BCG vaccine administration? Why?

A

Mantoux test

It should be negative, otherwise vaccination should result in secondary TB development

Year One - Respiratory System (14 decks)

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