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ESA 3 - Respiratory System > Tubercuosis > Flashcards

Tubercuosis Flashcards

1
Q

Who does TB primary affect?

A

Young adults - 15-59 that are non UK born.

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2
Q

What causes TB?

A

Microbacterium belonging to Mycobacterium tuberculosis complex.

There at seven closely related species - M tuberculosis, M Bevis, M africanum

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3
Q

What type of bacteria is TB?

A

Non-motile rod-shaped bacteria

Obligate aerobe

Long-chain fatty (mycolic) acids, complex waxes and glycolipids in cell wall. -Structural rigidity -Staining characteristics -Acid alcohol fast

Relatively slow-growing compared to other bacteria (generation time 15-20hrs)

Can’t gram stain TB -use ZN stain

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4
Q

How does TB spread?

A

Spread by respiratory droplets -coughing, sneezing..

Droplet nuclei / airborne (<10um particles, suspended in air, reach lower airway macrophage)

Infectious dose 1-10 bacilli

3000 infectious nuclei - cough, talking 5 mins

Air remains infectious for 30mins.

It is contagious but NOT easy to catch. You need prolonged exposure for ya least 8hours / day for up to 6 months.

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5
Q

Decree the pathogenesis of TB

A

Inhaled aerosols

Engulfed by alveolar macrophages

Local lymph nodes

Primary complex (progression to active disease -5%)

Initial containment of infectio

Latent infection - Heals / self cure or post primary TB

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6
Q

Describe the symptoms of latent TB

A

Inactive

Asymptomatic

Not infectious

Normal chest X-Ray

Negative sputum add cultures

Not a case of TB

TST or IFN gamma test results usually positive

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7
Q

Describe the symptoms of TB disease

A

Active -multiplying tubercle bacilli in the body

TST or blood tests usually positive

Chest x-ray usually abnormal

Sputum smears and cultures may be positive

Symptoms such a cough, fever, weight loss

Often infectious before treatment

A case of TB

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8
Q

What is a natural history of a primary TB patient?

A

Primary TB:

  • Ghon focus / complex (small area of granuloma tours tissue - sometimes visible in middle / lower area -subpleural)
  • Limited by Cell mediated immune response
  • Usually asymptomatic
  • Rare allergic reactions include EN
  • Occasionally symptomatic -miliary / disseminated
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9
Q

What is post-primary TB?

A

This is reactivation or exogenous re-infection 5 or more years after the primary infection.

There is a 5-10% risk per lifetime.

They can present with pulmonary or extra-pulmonary symptoms.

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10
Q

What are the risk factors for reactivation of TB?

A

Infection with HIV

Substance abuse

Prolonged therapy with corticosteroids and other immunosuppressive therapy

TNF-a antagonists

Organ transplant

Haematological malignancy

Severe kidney disease / haemodialysis

Silicosis

Low body weight

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11
Q

Where can Tb cause disease?

A

Lungs -Most frequent

Extra-pulmonary - found in HIV, immunosuppression or young children
Larynx 
Lymph node 
Pleura
Brain
Kidneys 
Bones and joints

Miliary TB - Rare
Carried to all parts of the body through the bloodstream.

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12
Q

Whats do you see on histology of TB?

A

Caseating granuloma.

-Langerhans giant cells.

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13
Q

When do you suspect TB?

A

Non-UK born / recent migrants - recent arrival or travel

HIV

Other immunocompromised states (cancer)

Homeless

Drug users, prison inmates

Close contacts of patients with TB

Specific clinical features: unexplained fever, weight loss, Malaise, Anorexia

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14
Q

What are the symptoms of TB?

A 
Fever 
Night sweats 
Weight loss and anorexia 
Tiredness and malaise 
Cough 
Haemoptysis occasionally 
Breathlessness if pleural effusion
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15
Q

What are the signs on examination of pulmonary TB?

A

No chest sings despite abnormal CXR
Maybe crackles in affected area

Extensive disease:

  • Signs of cavitation
  • Fibrosis

Pleural involvement - typically signs of effusion

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16
Q

How do you investigate TB?

A

Chest X-Ray

Sputum - 3 early morning samples minimum volume 5ml

Induced sputum

Bronchoscopy (dry cough)

17
Q

What does TB look like on an X-Ray?

A

Apex involved

Ill defined patchy consolidation

Cavitation usually develops within consolidation

Healing results in fibrosis

18
Q

What is TB microscopy?

A

Main way to diagnose Tb worldwide.

Rapid test, cheap

But, it cannot differentiate between NTM (non-infective tiberculosis mycobacterium) and MTB (mycobacterium tuberculosis)

Indicates infectiousness

60-70% of culture positive samples are microscopy positive.

19
Q

What is a TB culture?

A

Gold standard for TB diagnoses

One of most sensitive methods for detecting bacteria.

Allows identification of susceptibility testing

20
Q

What is NAAT?

A

Numeric acid amplification tests.

This is used for diagnosing positive smears (sputum tests) and also drug resistant mutations.

21
Q

Describe the histology of TB

A

Granuloma - Langerhans giant cells.

Caseous necrosis

22
Q

What is TST?

A

Tuberculin skin test

Inject tuberlin intradermally to see if patient has already been exposed to TB.

Used to work out who has been exposed to TB (not who is infected).

But, this is oder diagnostic test.

If patient has been infected before, will have redness and swelling.

23
Q

What are the problems with TST?

A

Antibody used is shared with other bacteria and BCG vaccine so can get false positives.

Can also get false negatives - immunocompromised e.g. HIV

Subjective interpretation - measuring redness.

24
Q

What is an IGRAs test?

A

Detection of antigen-specific IFN-gamma production

No cross reaction with BCG so no false positive.

Cannot diagnose latent TV and active TB.

25
Q

How do yo diagnose TB?

A

Radiology

Histolology

Microscopy

26
Q

How do you diagnose latent TB?

A

TST

IGRAs

27
Q

How do you treat TB?

A

At least four drugs! (RHZE) also vitamin D and maybe surgery to remove lung.

Use second line drugs if patients are intolerant or resistance.

Give combination to ensure it doesn’t become resistance to all drugs.

Early and adequate treatment with anti-TB drugs

Close monitoring of compliance

28
Q

Describe how drug resistance develops

A

Natural history - during multiplication small number of naturally drug resistant organisms arise through spontaneous mutations

Improper drug regimens / poor drug compliance leads to selection of these mutants

Single and multi drug resistance occurs

Diagnostic delays - overcrowding and inadequate infection control facilitates transmission of drug resistance.

29
Q

What is MDR?

A

Multi-drug distant TB.

This is when it is resistant to rifampicin and isoniazid

30
Q

What is XDR?

A

Extremely drug resistant TB

Resistant to rifampicin, isoniazid and fluoroquinolone and at least 1 injectable.

This is rare

31
Q

What increases risk of drug resistance?

A

Previous TB treatment
HIV+
Contact of MDR TB
Failure to response to conventional treatment
Over 4 months of positive smear (sputum) or 5 months of positive cultures.

32
Q

What is military TB?

A

Bacilli spreading through the bloodstream - widespread infection

Either during primary infection or during reactivation.

The lungs are always involved but fewer respiratory symptoms -fever, very well, dry cough.

Often multiple organs involved so can cause a variety of symptoms depending on what is involves. e.g. headaches (meninges), pericardial effusion, ascites,

33
Q

Where is extra-pulmonary TB common?

A

Lymphadenitis -scrofula, cervical LN, abscesses and sinuses

GI - shallowing of tubercles

Peritoneal - ascites or adhesive

Genitourinary - progress to renal disease and lower UT

Bones and joints - Haematogenous spread, spinal TB most common (Pott’s)

TB meningitis - chronic headache, fever, raised proteins and lymphocytes in CSF

34
Q

How do you prevent TB?

A

Have to notify public health about TB patients.

-Must start contact tracing and provide surveillance data to detect outbreaks and monitor epidemiological trends.

35
Q

How do you control TB?

A

Treat to make sure not infectious

While infectious:

  • PPI (special masks)
  • Negative pressure rooms

Reduce susceptible contacts

  • Address risk factors
  • Vaccination
36
Q

What is BCG?

A

A vaccine that is 70-80% effective in preventing severe childhood TB.

Given to children who’s parents come from high incidence areas.

37
Q

What are the four drugs used to treat TB and their side effects?

A

Rifampicin - raised transaminases and induces CP450, orange secretions.

Isoniazid - peripheral neuropathy, hepatotoxicity

Pyrazinamide - hepatotoxicity

Ethambutol - Visual disturbance

ESA 3 - Respiratory System (24 decks)

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