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hlb > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

What bacterium causes TB infection?

A
  • tubercule bacilli
  • mycobacterium tuberculosis (MTB) in humans
  • mycobacterium bovis for cows
  • non-tuberculous (atypical) mycobacterium does NOT cause tb but causes pulmonary diseases that resemble TB
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2
Q

What is the most common cause of infectious disease related mortality worldwide?

A

TB

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3
Q

how many new cases of TB a year?

A

9.6 million

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4
Q

What % of TB cases are HIV positive?

A

8%

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5
Q

increasing drug resistance in TB

A

1/2 million

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6
Q

What is the definition of high incidence of casees?

A

40/100,000

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7
Q

What % of TB cases in those born outside the UK?

A

72%

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8
Q

Who is at risk of TB?

A
  • Deprivation: homeless, malnutrition, overcrowding and vitamin D deficiency
  • alcohol abuse
  • prisons
  • immunocompromised: diabetes mellitus, HIV, steroid use
  • elderly
  • contact with high risk groups (travel to areas of high incidence)
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9
Q

How is TB transmitted?

A
  • spread by droplets from cough by people with pulmonary TB
  • bacillus inhaled into the lung
  • macrophages ingest bacillus and these replicate within the endosome
  • can then spread to other parts of the body
  • 80% of cases affect the lungs
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10
Q

Where/how can Tb spread to within the body?

A
  • haematogenous (bloodstream)
  • lymphatics to hilar lymph nodes and other lymph nodes
  • direct extension (eg pericardium)
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11
Q

Clinical presentation of pulmonary TB?

A
  • productive cough: not improving with standard antibiotics
  • haemoptysis
  • chest pain
  • fever
  • night sweats
  • fatigue
  • weight loss
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12
Q

Could your patient have TB abbreviation?

A
  • THINK TB
  • troublesome cough (3 weeks or longer)
  • Hemoptysis
  • Involuntary weight loss
  • Night sweats and fevers
  • Known exposure to TB
  • Tiredness
  • Breathlessness
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13
Q

TB initial hypersensitivity

A

acute presentation is similar to acute sarcoidosis
erythema nodosum (redness on arms and legs)
phlyctenular conjunctivitis (red spots around eyes)

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14
Q

Pathogenesis of TB

A

insert diagram

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15
Q

Progression of TB

A

insert diagram

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16
Q

Which is a latent infection of TB, cavitary TB, miliary TB?

A

insert diagram

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17
Q

Pulmonary MTB

A
  • majority of cases (55%)
    - infection risk
    - cavitary disease - more infections
  • Ghon Focus in lungs:
    • granuloma, area of central caseation and
      fibrosis
    • calcified with few dormant bacteria
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18
Q

MTB bacillus: features:

  • aerobic or anaerobic?
  • how often division occurs?
  • organelle features
  • gram positive or gram negative?
A
  • aerobic bacillus (needs O2 to live)
  • divides every 16-20 hours (slow)
  • cell wall, but lacks a phospholipid outer membrane
  • weakly gram positive
  • retains stans after treatment with acids = acid fast bacillus
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19
Q

Microbiological diagnosis of MTB

A
  • sputum/BAL
  • Ziehl-Neelsen stain = bright red bacilli on blue background
  • TB cultures 6-8 weeks:
    - confirm diagnosis
    - drug sensitivities
  • Nucleic acid amplification
    - identify MTB complex
    - distinguish from non-tuberculous
    infection
  • PCR:
    - mycobacterial DNA
    - pleural fluid/CSF/urine
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20
Q

Which stain used on this Tb?

INSERT DIAGRAM

A

Ziehl-neelson

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21
Q

Histology of MTB

A
  • granulomatous inflammation: rim of lymphocytes, fibroblasts, central infecteed macrophages
  • central necrosis: caseation
  • secretion of cytokines (IFN - gamma) which activates macrophages to kill bacteria
  • AFBs in granulomas
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22
Q

Mantoux/Tuberculin Test

A
  • 10 units (0.1ml) of Purified Protein Derivative (PPD) is injected intradermally and the size of the induration is measured after 48-72 hours
  • the cutaneous immune response is measured
  • response affected by the BCG vaccination status of the individual as those who have has the BCG vaccine will show a mild response even when they are not infected with MTB
  • a strong positive tuberculin response (Grade 3 or 4) should be investigated further with clinical assessment, chest x-ray and samples for culture as appropriate
  • > 5mm is positive
  • > 15mm is strongly positive
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23
Q

The mantoux test requires

A

circulating memory T lymphocyte ability to mount a delayed hypersensitivity reaction

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24
Q

Is the mantoux test specific?

A

No
cross reactive with other mycobacterial antigens so non-specific

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25
Q

When can the mantoux test be falsely negative?

A
  • in severely ill or immunocompromised individuals
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26
Q

IGRA/T spot test

A
  • the interferon gamma release assay is an in-vitro test that measures T-cell activation by MTB antigens
  • blood taken must be analysed within a few hours
  • The Quantiferon Gold assay and the T-spot TB assay are available in the UK
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27
Q

If a patient has a positive IGRA/T-spot test, do they have TB?

A
  • the results of these investigations must be interpreted carefully together will all the other information availble as a positive test on its own does not necessarily mean the patient has TB
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28
Q

Which is more specific; the mantoux test or the IGRA (interferon gamma release assay)?

A

Interferon Gamma Release Assay (IGRA)

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29
Q

Does the IGRA (interferon gamma release assay) correlate better with degree of exposure to TB than Mantoux?

A

Yes

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30
Q

Does the IGRA (interferon gamma release assay) differentiate between latent infection and disease?

A

No

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31
Q

Diagnosis of TB:

A
  • Hx of contact with smear positive Tb
  • signs and symptoms suggestive of TB
  • abnormal chest x ray
  • positive tuberculin/ positive T spot test
  • culture of mycobacterium TB
  • always consider a HIV test
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32
Q

CXR

A

insert

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33
Q

CXR

A

insert

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34
Q

CXR

A

insert

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35
Q

TB Disease progression:

A
  • primary TB (active):
    - 1-5% cases
    - bacilli overcome immune system soon
    after the initial infection
  • latent infection:
    - majority of cases (immune memory of
    exposure to TB)
    - 2-23% cases = reactivation of disease
    - risk of reactivation increases with
    immunosuppression
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36
Q

What % of patients never become ill with TB?

A

90% (unless they are HIV positive)

37
Q

What % of patients will progress to symptomatic and infectious TB (active TB)?

A

10%

38
Q

When are the chances of progressing to active TB the greatest?

A
  • within 1-2 years of infection and decrease steadily after this
39
Q

Active TB occurs by

A

reactivation of latent Tb or re-infection

40
Q

Latent TB vs Active TB:
- bacilli in/number?
- symptoms?
- sputum smear and culture positive or
negative?
- chest x ray normal or abnormal?
- Mantoux tuberculin test positive or negative
- IGRA test positive or negative
- infectious or not infectious?
- tuberculin skin test reaction?
- T spot blood test?

A

insert slide

41
Q

Differential diagnoses for TB:

A
  • bilateral hilar lymphadenopathy
  • clinical symptoms (B symptoms):
    - sarcoidosis
    - lymphoma
  • B symptoms: fever, drenching night sweats, weight loss
42
Q

Extrapulmonary MTB is more common in which ethnicity in the UK?

A
  • more common in non-UK born of asian origin
43
Q

Extrapulmonary MTB is generally a first infection or reactivation?

A

Reactivation of latent infection

44
Q

Extrapulmonary MTB: sites:

A
  • lymph nodes
  • CNS
  • Bone (Pott’s disease of the spine)
  • Genitourinary system
  • GI tract
  • disseminated = miliary TB
45
Q

TB lymphadenitis

A
  • often gets worse on treatment
  • paradoxical reaction
  • can form sinus tracts with chronic discharge
  • cold abscess formation
46
Q

TB lymphadenitis

A

insert

47
Q

Disseminated Miliary TB symptoms and percentage of patients that experience this

A
  • fevers, sweats, weight loss and malaise very common
  • respiratory symptoms in majority
  • GI or CNS Symptoms in 20%:
    - abdominal pain, diarrhoea, abnormal
    LFTs
    - hepatomelagy in 50%
    - headache or confusion; altered mental
    state in 20%
48
Q

miliary TB CXR

A

insert

49
Q

miliary TB CT

A

insert

50
Q

Extrapulmonary TB can affect (5):

A
  • pericardium
  • skeleton
  • genitourinary
  • eye
  • gastrointestinal
51
Q

Tuberculous meningitis can affect

A

the central nervous system

52
Q

TB can also be found in cerebral spinal fluid.

True or False?

A

True

53
Q

Extrapulmonary TB is most commonly found in those who are

A

co-infected with HIV

54
Q

Mortality from extrapulmonary TB

A

15-40%

55
Q

Historical treatment of MTB:

A
  • sanitorium
  • surgical treatments:
    - thoracoplasty
    - rib resection
    - lobectomy
    - pneumonectomy
    - artificial pneumothorax
    - plombage
  • streptomycin (1950s)
56
Q

Standard Quadruple Therapy for TB: First Line Drugs: Initial phase:

(how many months treatment?)

A
  • 2 months
  • isoniazid
  • rifampicin
  • pyrazinamide
  • ethambutol
57
Q

Standard Quadruple Therapy TB: First Line Drugs: Continuous Phase:

(how many months treatment?)

A
  • 4 months
  • isoniazid
  • rifampicin
58
Q

First Line Drugs: TB meningitis: how long?

A
  • TB meningitis
  • affects central nervous system
  • 12 months
59
Q

Side effects of drug treatment for MTB (4)(1):

A
  • Pyrazinamide: Hepatoxicity, joint pain, N&V
  • Rifampicin: Hepatoxicity, reddish colour to
    the urine, tears
  • Isoniazid: Hepatoxicity ,fever, peripheral
    neuropathy and optic neuritis
  • Ethambutol: peripheral neuropathy, optic
    neuropathy and gout
  • All: nausea and skin rashes
60
Q

What does MTRB stand for?

A
  • multi-drug resistant TB
61
Q

When does MDRTB occur?

A
  • failure of treatment with first line drugs: lack of compliance
62
Q

MDRTB mainly occurs in which conntinents?

A

majority from africa or indian sub-continent

63
Q

Why has rated of MDRTB doubled in the UK?

A

Immigration

64
Q

Patients with MDRTB must be —— as they pose a huge public health risk

A

isolated

65
Q

What % of all TB deaths are caused by MDRTB worldwide?

A

10%

66
Q

To treat MDRTB

A

a prolonged course of second line drugs for upto 24 months may be required
third line drugs sometimes required

67
Q

Why should patients complete treatment?

A

to reduce the risk of:
- drug resistant TB
- onward transmission
- relapse of disease
- dying

68
Q

What % of TB patients complete a six month treatment?

A

83%

69
Q

TB is curable with

A

antibiotics

70
Q

Latent TB treatment

A
  • 3 months of rifampicin and isoniazid
  • 6 months of izoniad
71
Q

Screening for latent TB:

A
  • close contacts of index case
  • pre-employment for healthcare workers
  • some new entrant to UK “looked after children”
  • those who are going to have biologics treatment (immunosuppressive): Rheumatoid arthirits, Crohn’s disease, Psoriasis
72
Q

Prevention of spread of TB:

A
  • BCG vaccination
  • contract tracing
  • directly observed therapy (DOT)
  • problems with TB treatment: stigma
73
Q

BCG vaccination

A
  • the only vaccine available against TB
  • 70-80% protection against severe and disseminated TB in children, but its protective efficacy against adulthood, pulmonary TB is limited
  • offer to infants aged 0-4 weeks
  • if born in high incidence area
  • if parent or grandparent born in high incident area
  • if family history of TB in the last 5 years
  • reduces risk of TB meningitis and miliary /tb
74
Q

What is the cornerstone of TB control?

A

contact tracing

75
Q

Index case?

A

the patient with TB is identified

76
Q

Contact Tracing:

A
  • close household contacts
  • if any of these are positive, then extend: other family members, school, work etc
77
Q

Contact tracing for TB: screening of contacts:

A
  • chest x ray
  • IGRA
78
Q

Contact Tracing for TB: screened contacts show chest x ray normal and IGRA positive, what is the next course of action?

A
  • latent TB treatment
79
Q

Contact Tracing for TB: screened contacts show chest x ray abnormal, symptoms and positive IGRA, what is the next course of action?

A

6 month TB treatment

80
Q

Directly Observed Therapy (DOT)

A
  • used in treatment of Tb
  • to ensure compliance
  • adults who need supervision:
    - alcoholics
    - chaotic lifestyle
    - previous TB
    - mental health problems
  • done in hospital/via videa/local pharmacy
  • recommendation daily tablets
  • if not possible then 3x a week
  • lack of compliance results in a poor outcome, development of multi-drug resistant TB
81
Q

Monitoring of TB treatment

A
  • blood tests (liver function) at baseline
  • Ishihara test to check if you are going colour blind
  • colour vision
  • monitor liver function tests
82
Q

34 year old male cleaner born in Zimbabwe, in UK last 10 years. Recent productive cough last few months with a 2 day history of haemoptysis, decreased appetite and weight loss 10 kg over 6 months . No history of travel in last year. Had BCG ( TB vaccine ) as a child. Smoker 4-5 /day.

On examination: thin, moist cough, afebrile, not clubbed, no lymphadenopathy , respiratory rate 18 /min normal, chest expansion and percussion normal, crackles right upper zone, O2 saturation 95%, pulse normal and heart rate 90/min heart sounds normal, no organomegaly.

What exams to be ordered?

A

CXR
Sputum:
IGRA

83
Q

2 year old child contact traced as contact of aunt living in household diagnosed with smear positive, fully sensitive MTB
Initially asymptomatic, Mantoux negative, T Spot negative with index case on Rx for 2 weeks
Missed BCG child of Nepalese parents

what happens next?

A

repeat mantoux test in 6 weeks

84
Q

2 year old child contact traced as contact of aunt living in household diagnosed with smear positive, fully sensitive MTB
Initially asymptomatic, Mantoux negative, T Spot negative with index case on Rx for 2 weeks
Missed BCG child of Nepalese parents
Repeat at 6 weeks Mantoux positive 10 mm

What examinations ordered?

A

T spot
Full blood count
chest x ray

85
Q

2 year old child contact traced as contact of aunt living in household diagnosed with smear positive, fully sensitive MTB
Initially asymptomatic, Mantoux negative, T Spot negative with index case on Rx for 2 weeks
Missed BCG child of Nepalese parents
Repeat at 6 weeks Mantoux positive 10 mm

T Spot positive; Fbc ESR LFTs all negative ;CXR normal

What diagnosis?

A

latent TB

86
Q

2 year old child contact traced as contact of aunt living in household diagnosed with smear positive, fully sensitive MTB
Initially asymptomatic, Mantoux negative, T Spot negative with index case on Rx for 2 weeks
Missed BCG child of Nepalese parents
Repeat at 6 weeks Mantoux positive 10 mm

T Spot positive; Fbc ESR LFTs all negative ;CXR normal = latent TB

what treatment prescribed?

A
  • treated 3 months anti-TB drugs
  • isoniazia
  • rifampicin
  • vitamin supplement pyridoxine
87
Q

What differentiates between Active and Latent TB?

1 = AFB in sputum
2 = Age of patient
3 = Positive Mantoux test
4 = Positive IGRA test
5 = Previous BCG vaccination

A

1

88
Q

A 27 year old doctor arrives in the UK to work for the NHS. He is very well. His pre-employment health check reveals a normal CXR and a positive IGRA test. What treatment, if any, does he require?

1 = BCG vaccination
2 = 3 months of quadruple therapy
3 = 3 months of Isoniazid and Rifampicin
4 = 6 months of quadruple therapy
5 = No treatment needed

A

3

89
Q

Which of these is a risk factor for developing active TB?

1 = living in low altitude
2 = male gender
3 = malnutrition
4 = obesity
5 = smoking

A

3

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