Mycobacteria tuberculosis Flashcards Preview

Microbiology Block 3 > Mycobacteria tuberculosis > Flashcards

Flashcards in Mycobacteria tuberculosis Deck (36):
1

Biology?

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

2

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

bright red bacilli

3

what is mycobacterias wall made of?

Mycolic acid  & Lipid-Rich Wall

4

M. tuberculosis can be cultured on what medium?

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

5

Transmission?

Human-to-human aerosol

6

when is there High mortality with Mycobacteria tuberculosis?

HIV co-infection

7

what are the virulence factors?

Mycolic acids

Cord factor

Lipoarabinomannan (LAM)

 

8

Mycolic acids are responsible for what?

 protects against free radicals

 

prevents complement activation.

9

what will Cord factor do?

Prevents phagosome fusion with lysosome

 

10

what will Lipoarabinomannan (LAM) do?

 

Inhibits macrophage activation and prevents phagosome fusion

11

what are the minor virulence factors?

Superoxide Dismutase & Catalase

PDIM

19 kDa lipoprotein

 

12

Superoxide Dismutase & Catalase does what?

Neutralizes  ROS (Reactive Oxygen Species) inside macrophages

13

PDIM does what?

Helps multi-cellular macrophage fusion (Giant Cell)

14

19 kDa lipoprotein does what?

Suppresses pro-inflammatory cytokines

15

Pathogenesis?

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. 

16

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

CMI

17

how do Large granuloma, associated with disease look like?

Necrotic caseous core with fibrin and liquid 

 

18

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

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

19

what are the symptoms of Primary Tuberculosis?

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

what is Pulmonary Tuberculosis?

Persistent cough with mucous; sometimes with blood

  • Chest pain
  • Dyspnea
  • Weight loss

 

21

Primary tuberculosis Occurs in what individuals?

individuals lacking previous contact with tubercle bacilli

22

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

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

what is the Ghon complex?

combination of Ghon focus and Hilar lymph node involvement

24

what symptoms are seen in Chronic state Pulmonary tuberculosis?

Fibrosis, scaring

Calcification 

Persist for life

Show up as radio-opaque nodules

25

identify?

Q image thumb

ghon complex

26

identify

Q image thumb

ghon focus

27

what is secondary TB?

  • 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

Clinical findings of secondary TB?

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

29

what is Miliary Tuberculosis?

  • 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

what are the complications of miliary TB?

  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

what is the skin test for M tuberculosis?

Mantoux tuberculin test   

 - CMI response to PPD

32

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

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

33

how is TB treated?

Isoniazid (Mycolic acid)

Rifampin (RNA Pol)

Pyrazinamide (cell wall)

Ethambutol (membrane)

 

34

how do you treat multi-drug resistant TB?

Pyrazinamide

Ethambutol

35

what vaccine is used to prevent TB?

BCG Vaccine (Bacillus Calmette-Guérin)

36