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Year 5 Pathology > Mycobacterial Disease > Flashcards

Mycobacterial Disease Flashcards

1
Q

What can you divide mycobacteria into?

A

Mycobacteria are divided into slow-growing and rapid-growing mycobacteria

  • <7 days = rapid grower
  • >7 days = slow grower
  • Leprosy not grouped as cannot be grown
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2
Q

types of mycobacterium

A
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3
Q

Mycobacterium microbiology

A
  • Non-motile rod-shaped bacteria (structurally gram +ve)
  • Relatively slow growing compared to other bacteria
  • Long-chain fatty (mycolic) acids, complex waxes and glycoproteins in cell wall
    • Structural rigidity
    • Complete Freund’s adjuvant
    • Staining characteristics
  • Acid-alcohol fast bacilli (AAFBs)
  • Staining: Auramine (screening), Z-N (diagnosis

Mycolic acid provides staining properties and alcohol resistant

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4
Q

NTB Mycobacterium features

A
  • Ubiquitous
  • Environmental (i.e. water and soils)
  • Atypical
  • Spectrum of pathogenicity (majority are not pathogenic to humans) and may be found colonising (not infecting)
  • Not transmitted person-to-person
  • Commonly resistant to the usual anti-TB therapy
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5
Q

Slow growing NTM

A
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6
Q

Rapid-growing NTM

A
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7
Q

NTM epidemiology

A
  • Ontario (MAI/C incidence high), Netherlands (incidence NTM increasing over MTB)
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8
Q

RFs for NTM

A

age

underlying lung disease

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9
Q

NTM Diagnosis

A
  • BTS Guidelines 2017
  • American Thoracic Society Guidelines
  • Combines clinical findings with microbiology findings (blood culture, bronchoalveolar lavage, biopsy)
  • Exclude other diagnoses
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10
Q

NTM Tx

A
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11
Q

2 types of mycobacterium leprae

A

Paucibacillary tuberculoid

  • Few skin lesions + less joint infiltration
  • Robust T cell response

Multibacillary lepromatous

  • Abundance of bacilli
  • Multiple skin lesions + joint infiltration
  • Poor T cell response
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12
Q

MTB: epidemiology, disease states, MTB complex, transmission, prevention

A
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13
Q

Natural history of MTB (primary, latent, reactivation)

A
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14
Q

post-primary TB: Risk factors, and clinical presentations

A
  • Post-Primary TB = a reactivation or exogenous re-infection:
    • Happens >5 years after initial infection
    • 5-10% lifetime risk
  • Risk Factors for Reactivation:
    • Immunosuppression
    • Chronic alcohol excess
    • Malnutrition
    • Ageing

Clinical Presentation:

  • Pulmonary or extra-pulmonary
  • Host immune response shapes the clinical outcome – SEE ABOVE
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15
Q

MTB diagnosis

A
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16
Q

Pulmonary vs extra-pulmonary disease

A
17
Q

MTB: clinical approach, RFs, presentation

A
18
Q

MTB Ix’s

A
19
Q

MTB Smear → culture and staining:

A
  • Sputum (60% sensitivity, but increases with additional samples → hence, 3 samples)
  • Gastric aspirated in children
  • Rapid
  • Operator-dependent
20
Q

Tx of MTB

A
21
Q

Side effects of RIPE

A
22
Q

TB adherence

A
  • Direct observation therapy / DOTS
  • Video observed therapy / VOTS
23
Q

Types of resistance and cause

A

Multi-Drug Resistant (MDR) → resistant to rifampicin and isoniazid

Extremely Drug Resistant (XDR) → resistant to rifampicin, isoniazid, fluoroquinolones and at least 1 injectable

  • Due to spontaneous mutation + inadequate treatment
  • They require a 4/5-drug regimen of longer duration (9-12m)
  • Quinolones + aminoglycosides + para-aminosalicylic acid (PAS) + cycloserine + ethionamide
  • Current WHO recommendations state that 7 drugs should be used for 9-12 months
  • Risks side effects for longer…
24
Q

when does risk of drug-resistant TB increase?

A

previous TB tx

known contact with MDR TB

HIV+

Failure to respond to conventional TB

25
Q

HIV and TB co-infection: diagnostic and tx challenges

A

Diagnostic Challenges:

  • Clinical presentation is less likely to be classical with symptoms and signs absent if low CD4+
  • CXR may be normal (more likely to have extra-pulmonary manifestations)
  • Smear microscopy and culture is less sensitive
  • Tuberculin skin test is more likely to be negative
  • Low sensitivity of IGRAs

Treatment Challenges:

  • Timing of treatment initiation
  • Drug interactions
  • Overlapping toxicity
  • Duration of treatment (adherence)
  • Healthcare resources

Year 5 Pathology (27 decks)

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