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Jess Resp > TB > Flashcards

TB Flashcards

1
Q

Which organism causes TB and how would you stain it? How does transmission usually occur?

A

mycobacterium tuberculosis, stained with ziehl Nielsen. The transmission is usually by aerosol

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2
Q

Upon infection, how might you initially present?

A

Only 5% will go on to develop symptomatic TB, TB will initially enter and become dormant so the majority of hosts will be asymptomatic

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3
Q

What is the lifetime risk of those infected with TB developing the active disease?

A

10%

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4
Q

What happens during the initial infection?

A

The primary infection occurs on first exposure
1. M TB is phagocytosed by alveolar macrophages, but the bacterium prevents phagolysosomes from occurring so it isn’t initially killed. The bacterium can also grow intracellular

  1. These macrophages initiate the development of cell-mediated immunity produces lymphokines and infiltration of lymphocytes and activated macrophages with enhanced ability to kill TB
  2. A TB granuloma forms over 2-3 months
  3. Other cells react and deposit collagen fibres to enclose the infected macrophages within the tubercle, the infected cells in the centre die releasing M TB.
  4. This produces a caseous necrotic core surrounded by epithelioid macrophages, Langerhans giant cells and lymphocytes; Ghons focus
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5
Q

How is the ghons focus and ghons complex formed?

A
  1. Ghons focus: is formed from the caseous necrotic granuloma that is holding the initial TB infection, which may be in any lung zone
  2. If the infection is not controlled in that local site, TB bacilli drain from the ghons focus into the hilar lymph nodes. The primary ghons focus + draining (hilar) lymph nodes form the ghons complex/primary complex
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6
Q

How do most primary/ghons complexes heal?

A

Most heal with or without calcification.

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7
Q

What can happen right before healing of the ghons complex occurs and what is the inevitable result of this?

A

Before healing, some TB bacilli can enter the bloodstream (likely via lymph drainage to the venous system).

This hematogenous spread results in the seeding of the bacilli to other parts of the lung and other organs and may potentially be reactivated (latent TB)

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8
Q

When does secondary TB occur?

A

Post-primary/Secondary/Latent TB occurs when M tuberculosis ruptures from the tubercle and re-establishes the infection, this may happen either when

  1. The patient’s immune mechanisms wane or fail
  2. The patient is re-exposed
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9
Q

How can you detect latent TB, can it tell you everything about the disease?

A

A positive tuberculin skin test, as the test demonstrates a type IV hypersensitivity reaction to proteins derived from mycobacteria. However, it cannot indicate if the disease is active, merely just if there has been exposure to the organism

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10
Q

What is the risk of developing another active TB following resolution of the first?

A

5%

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11
Q

How does primary TB occur?

A

If the initial ghons complex was unable to heal

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12
Q

Where is post-primary TB often seen?

A

Often seen in the upper lung zones as the higher ventilation/perfusion ratio is believed to predispose reactivation of TB bacilli at these sites

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13
Q

Which individuals are at higher risk of developing TB?

A
  1. close contacts of persons suspected of TB
  2. elderly
  3. residents of high TB prevalent areas
  4. immunocompromised individuals
  5. patients with a history of poorly treated TB
  6. homeless, IV drug users
  7. patients in high risk congregate settings; prison, shelters, nursing homes, etc.
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14
Q

What 4 characteristics should make you always consider TB?

A
  1. resistance to simple antibiotics
  2. febrile (fever-like) illness
  3. chest infection
  4. unexplained cough
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15
Q

How does hemoptysis occur?

A

Through hemorrhage resulting from the extension of the caseous process into vessels of the cavity walls

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16
Q

How does tuberculous pneumonia occur?

A

marked inflammatory exudate filling the alveoli causes consolidation

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17
Q

How can a pleural effusion result from TB?

A

Seeding of the TB bacilli in the pleura, or hypersensitivity

18
Q

Name 6 symptoms of TB?

A
  1. cough
  2. tiredness and malaise
  3. weight loss and anorexia
  4. fever (low grade)
  5. hemoptysis
  6. breathless if pleural effusion
19
Q

Name 5 signs of TB

A
  1. palpable lymph nodes in 10%
  2. weight loss
  3. finger clubbing in long-standing disease
  4. fever
  5. pallor
20
Q

How could you get miliary TB? Name 3 spots you could get more localized reactivation

A 
If the rupture of caseous pulmonary focus gets into a blood vessel
More localized reactivation:
1. pleura
2. lymph nodes
3. parts of the skeleton
21
Q

Name some characteristics of pleural TB

A

More common in males, can cause tuberculous empyema

22
Q

Name some characteristics of lymph node TB, which lymph nodes tend to be affected?

A

More common in women, children and asians. Often painless and most commonly cervical lymph nodes; can be discrete swelling to marked skin inflammation and rupture

23
Q

What is the most common consequence of osteo-articular TB? What is it, and name 3 other possible osteo-articular TB consequences.

A

Most common is tuberculous spondylitis; starts in sub-chondral bone, follows longitudinal ligaments, mainly lower thoracic and upper lumbar spine and may progress to paralysis

Other: peripheral arthritis, osteomylitis, dactylitis, tendosynovitis

24
Q

What does tuberculous spondylitis resemble?

A

Kyphosis

25
Q

What investigatory tests could you run for pulmonary tuberculosis?

A

Chest x ray, sputum test for acid fast bacilli + bronchoscopy, biopsy, lavage

26
Q

How might TB appear on a chest X ray?

A

Patchy solid lesions, cavitated solid lesions, streaky fibrosis, calcified flecks

27
Q

Compare auramine to ziehl neelsen staining

A

auramine is more sensitive and is more suitable for assessment of smears

28
Q

What does ziehl neelsen stain provide?

A

Morphological details and is useful for examination of acid fast bacilli in cultures

29
Q

Do negative smears exclude TB?

A

No

30
Q

How does Interferon gamma release assay work?

A

Put TB antigens onto a tissue sample and look for T cell reactivity and measure the release of intereferon gamma

31
Q

What is the role of steroids in treatment of TB?

A

Prevention of complications

32
Q

How would you treat TB?

A

With a combination of antibiotics to limit development of resistance

33
Q

Compare and contrast interferon gamma release assay over the mantoux test

A

The mantoux test can cross-react with the BCG and falsely indicate TB (bovine/deactivated TB), so IGRA is more sensitive but more expensive. Mantoux test also cannot distinguish between latent and active TB.

34
Q

What 4 drugs would you give as first line 2 month drugs and which 2 would you continue on for an additional 2 months? l?

A
  1. rifampicin
  2. isoniazid
  3. pyrazinamide
  4. ethambutol

Rifampicin, isoniazid continue for 4 months

35
Q

Which drugs are multidrug-resistant TB and extensively drug-resistant TB resistant to?

A

First line drugs and second line injectable drugs like amikacin

36
Q

Which individuals are at increased risk of drug-resistant TB?

A
  1. contact of patients with drug resistant TB
  2. individuals who come from areas where high resistant TB prevalence is high
  3. person whose smears remain positive after therapy
  4. person who received inadequate treatment for > 2 weeks
  5. patients with HIV
37
Q

What is contact tracing?

A

Uses the 8 hour cumulative exposure rule: should screen any close contacts of someone who has been diagnosed with TB

38
Q

What is the stone in the pond principle?

A

Determines which entities around the patient are eligible for screening: household, workplace, leisure

39
Q

How effective is the BCG vaccination against TB?

A

70-80% effective

40
Q

What material is abundant in Mycobacterium tuberculosis’ structure? What characteristics does the presence of this material bestow? (name four)

A

Has mycolic acid

  1. Slow growing
  2. Protection from lysis once phagocytosed
  3. Ability to grow intracellular
  4. Resistance to gram staining
41
Q

When does disseminated TB occur?

A

When infected macrophages carry the bacteria systemically to different sites of the body

Jess Resp (20 decks)

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