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Infectious Diseases > TB/NTM > Flashcards

TB/NTM Flashcards

1
Q

What type of bacteria is Mycobacterium tuberculosis?

A

Acid fast bacillus (mycolic acid makes it impervious to gram staining)

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2
Q

What is the leading cause of infectious death

A

Tb

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3
Q

What percentage of children encounter delays in diagnosis of TB

A

90%

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4
Q

What are the three trajectories for TB infection in children?

A
  1. Immediate killing (TST/IGRA negative)
  2. Latent TB (TST/IGRA positive), can lead to reactivation
  3. Primary progressive TB
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5
Q

How do children often acquired Tb?

A

Close contact with infectious adult case

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6
Q

90% of children who progress to TB disease do so within ___ years of infection

A

1 year

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7
Q

What is latent Tb

A

Asymptomatic, well child, normal CXR, TST/IGRA positive

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8
Q

How does Pulmonary TB present

A

Fever, cough, weight loss, lethargy. 50% are still asymptomatic, found through contact tracing

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9
Q

Clinical presentations of TB

A
  1. Latent TB
  2. Pulmonary TB
  3. Extrapulmonary TB (TB adenitis, TB meningitis, TB percarditis, TB peritonitis, BJI)
  4. Miliary TB
  5. Congenital TB
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10
Q

Diagnosis of TB

A
  1. TST (Mantoux)
  2. Qunatiferon Gold (IGRA)
  3. AFB smear
  4. Rapid PCR
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11
Q

How does TST work

A

Intradermal injection with purified protein derivative. Read at 48 - 72 hours. Positive result = LTB or TB disease, negative test doesn’t rule out TB disease

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12
Q

How does IGRA work

A

Measures IFN-y in blood in response to TB antigens. Positive result = LTB or TB disease, negative test doesn’t rule out TB disease

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13
Q

What is ELI-spot/T spot

A

Number of peripheral mononuclear cells that make IFN-y after antigen stimulation

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14
Q

What is AFB smear

A

x3 resp samples or x3 early morning gastric aspirates (most children smear negative due to pauci-bacillary disease)

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15
Q

How do rapid molecular methods work

A

PCR. Can also detect rPOB gene which predicts rifampicin resistance. Highly specific, 98%

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16
Q

Classic imaging findings TB on CXR

A

Hilar lymphadenopathy, lobar consolidation, diffuse small nodules (milliary), RUL involvement (adolescents), pleural effusions, cavitations

17
Q

TB Treatment

A

LTBI: 3 months RH or 6 months H
TB disease: 2 months RHZ + 4 months RH

18
Q

SHINE trial

A

4 months treatment was non inferior to 6 months for TB disease that is non severe, smear negative and not drug resistant (2 RHZ + 2 RH)

19
Q

TB drugs

A

R = Rifampicin
H = Isoniazid
Z = Pyrazinamide
E= Ethambutol

20
Q

Disseminated TB treatment

A

12 months total

21
Q

Adjunct to TB drugs

A

Steroids (if TB meningitis, airway obstruction, pericardial, milliary)
Pyridoxine to prevent Isoniazid peripheral neuropathy in breast fed babies, adolescents, malnourished child, HIV positive, peripheral neuropathy

22
Q

Side effects of TB treatment

A

RHZ = LFT derangement
E = Optic neuritis and red green colour blindness
H = Peripheral neuritis

23
Q

What is BCG vaccine made from

A

Mycobacterium bovis isolate, live attenuated vaccine

24
Q

How effective is BCG vaccine

A

80% effective against severe forms (Milliary + miliary) in young infants

25
Q

How does BCG affect TB diagnostic tests

A

Can cause false positive TST, no impact on IGRA

26
Q

Side effects of BCG vaccine

A

Local scar, injection site abscess, regional adenopathy, osteitis, disseminated BCG disease

27
Q

Where are NTM found

A

Soil, food water animals

28
Q

Most common NTM

A

Mycobacterium avium intracellulare (MAIC)

29
Q

Most common clinical manifestation of NTM

A

Lymphadenitis

30
Q

What is MSMD

A

Mendelian Susceptbility to Mycobacterial Disease, caused by IL-12 deficiency and interferon gamma receptor defects. Occurs post HSCT, in HIV. Impaired cell mediated immunity

31
Q

Spectrum of NTM infections

A

Cutaneous, disseminated, pulmonary (Bx, CF, PCD)

32
Q

Diagnosis of NTM

A

Culture/PCR
TST may be positive with MAIC cervical lymphadenitis
IGRA has less cross reactivity for MAIC and most other NTM species

33
Q

Types of NTM

A

MAIC, M. fortuitum, M. absessus, M marinarum

34
Q

Treatment for MAIC adenitis

A

Natural history is slow resolution
1. Excision
2. I&D risks sinus and fistula formation
3. If resection not possible, consider Clarithromycin/Azithromycin + Ethambutol +/- Rifampicin

35
Q
A

Infectious Diseases (9 decks)

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