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Microbiology Block 3 > Mycobacteria tuberculosis > Flashcards

Mycobacteria tuberculosis Flashcards

1
Q

Biology?

A
  • Obligate Aerobic bacilli
  • Acid-fast bacteria (red)
  • Mycolic acid cell wall
  • very fastidious
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2
Q

how does M. tuberculosis appear in a sputum smear stained with the Ziehl-Neelsen stain?

A

bright red bacilli

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3
Q

what is mycobacterias wall made of?

A

Mycolic acid & Lipid-Rich Wall

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4
Q

M. tuberculosis can be cultured on what medium?

A

Lowenstein-Jensen (LJ) Media (Typical small, buff coloured colonies of)

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5
Q

Transmission?

A

Human-to-human aerosol

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6
Q

when is there High mortality with Mycobacteria tuberculosis?

A

HIV co-infection

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7
Q

what are the virulence factors?

A

Mycolic acids

Cord factor

Lipoarabinomannan (LAM)

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8
Q

Mycolic acids are responsible for what?

A

protects against free radicals

prevents complement activation.

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9
Q

what will Cord factor do?

A

Prevents phagosome fusion with lysosome

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10
Q

what will Lipoarabinomannan (LAM) do?

A

Inhibits macrophage activation and prevents phagosome fusion

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11
Q

what are the minor virulence factors?

A

Superoxide Dismutase & Catalase

PDIM

19 kDa lipoprotein

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12
Q

Superoxide Dismutase & Catalase does what?

A

Neutralizes ROS (Reactive Oxygen Species) inside macrophages

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13
Q

PDIM does what?

A

Helps multi-cellular macrophage fusion (Giant Cell)

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14
Q

19 kDa lipoprotein does what?

A

Suppresses pro-inflammatory cytokines

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15
Q

Pathogenesis?

A

Primary infection:

  • tuberculosis are engulfed by alveolar macrophages (survive and multiply). Non-resident macrophages attracted.
  • fusion of macrophages to form Langhans giant cells.
  • If bacterial load is high, dendritic cells transport Mtb antigens via lymphatics to hilar lymph nodes.
  • Cell Mediated Immune (CMI*) Response is stimulated.
  • Th1 cells migrate to lungs to activate uninfected macrophages and surround the infected macrophages and free bacteria via granuloma formation.
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16
Q

what leads to formation of “tubercles/granulomas” which encase live Mycobacteria tb and prevent further disease progression?

A

CMI

17
Q

how do Large granuloma, associated with disease look like?

A

Necrotic caseous core with fibrin and liquid

18
Q

what If host immune response is weakened at a later point in time (ex. AIDS)?

A

cavitation, or bursting of contained Mtb in granuloma, will occur, causing re-activated Tuberculosis disease.

19
Q

what are the symptoms of Primary Tuberculosis?

A

usually asymptomatic

Produces a calcified granuloma or area of scar tissue

(May be a origin for reactivation or Secondary TB)

** Progressive Primary TB may be symptomatic**

20
Q

what is Pulmonary Tuberculosis?

A

Persistent cough with mucous; sometimes with blood

  • Chest pain
  • Dyspnea
  • Weight loss
21
Q

Primary tuberculosis Occurs in what individuals?

A

individuals lacking previous contact with tubercle bacilli

22
Q

what is seen in the Sub-pleural location in pulmonary TB?

A

Ghon focus (granuloma): 1-1.5 cm gray white area of caseous necrosis in sub-pleural location.

(Tubercle bacilli then drain to the regional lymph nodes)

23
Q

what is the Ghon complex?

A

combination of Ghon focus and Hilar lymph node involvement

24
Q

what symptoms are seen in Chronic state Pulmonary tuberculosis?

A

Fibrosis, scaring

Calcification

Persist for life

Show up as radio-opaque nodules

25
Q

identify?

A

ghon complex

26
Q

identify

A

ghon focus

27
Q

what is secondary TB?

A
  • Reactivation of dormant Mtb,
  • Original granuloma bursts or cavitates
  • Usually at the apex of the lung
  • Frequently, its a consequence of impaired immunity
  • Involves one or both apices in upper lobes (Ventilation (oxygenation) is greater in upper lobes)
28
Q

Clinical findings of secondary TB?

A

Cough, Fever, drenching night sweats, weight loss and hemoptysis.

29
Q

what is Miliary Tuberculosis?

A
  • disseminated TB
  • particularly immunocompromised
  • Can occur after primary exposure or re-activated secondary TB.
  • Spreads via blood stream in macrophages
  • Tubercles found in many tissues
  • Cancer-like wasting*
30
Q

what are the complications of miliary TB?

A
  1. Miliary spread in lungs due to invasion into the bronchus or lymphatics
  2. Miliary spread to extra-pulmonary sites
  • Due to invasion of pulmonary vein tributaries
  • Kidney is the MC extra-pulmonary site
31
Q

what is the skin test for M tuberculosis?

A

Mantoux tuberculin test

  • CMI response to PPD
32
Q

how is a diagnosis with M. Tb confirmed? what does this do?

A

QuantiFERON-TB Test; Test quantitates Interferon γ production by pre-sensitizes cells

33
Q

how is TB treated?

A

Isoniazid (Mycolic acid)

Rifampin (RNA Pol)

Pyrazinamide (cell wall)

Ethambutol (membrane)

34
Q

how do you treat multi-drug resistant TB?

A

Pyrazinamide

Ethambutol

35
Q

what vaccine is used to prevent TB?

A

BCG Vaccine (Bacillus Calmette-Guérin)

36
Q
A

Microbiology Block 3 (39 decks)

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