Mycobacteria tuberculosis

Question 1

Biology?

Answer 1

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

Question 2

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

Answer 2

bright red bacilli

Question 3

what is mycobacterias wall made of?

Answer 3

Mycolic acid & Lipid-Rich Wall

Question 4

M. tuberculosis can be cultured on what medium?

Answer 4

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

Question 5

Transmission?

Answer 5

Human-to-human aerosol

Question 6

when is there High mortality with Mycobacteria tuberculosis?

Answer 6

HIV co-infection

Question 7

what are the virulence factors?

Answer 7

Mycolic acids

Cord factor

Lipoarabinomannan (LAM)

Question 8

Mycolic acids are responsible for what?

Answer 8

protects against free radicals

prevents complement activation.

Question 9

what will Cord factor do?

Answer 9

Prevents phagosome fusion with lysosome

Question 10

what will Lipoarabinomannan (LAM) do?

Answer 10

Inhibits macrophage activation and prevents phagosome fusion

Question 11

what are the minor virulence factors?

Answer 11

Superoxide Dismutase & Catalase

PDIM

19 kDa lipoprotein

Question 12

Superoxide Dismutase & Catalase does what?

Answer 12

Neutralizes ROS (Reactive Oxygen Species) inside macrophages

Question 13

PDIM does what?

Answer 13

Helps multi-cellular macrophage fusion (Giant Cell)

Question 14

19 kDa lipoprotein does what?

Answer 14

Suppresses pro-inflammatory cytokines

Question 15

Pathogenesis?

Answer 15

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.

Question 16

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

Answer 16

CMI

Question 17

how do Large granuloma, associated with disease look like?

Answer 17

Necrotic caseous core with fibrin and liquid

Question 18

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

Answer 18

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

Question 19

what are the symptoms of Primary Tuberculosis?

Answer 19

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**

Question 20

what is Pulmonary Tuberculosis?

Answer 20

Persistent cough with mucous; sometimes with blood

• Chest pain
• Dyspnea
• Weight loss

Question 21

Primary tuberculosis Occurs in what individuals?

Answer 21

individuals lacking previous contact with tubercle bacilli

Question 22

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

Answer 22

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)

Question 23

what is the Ghon complex?

Answer 23

combination of Ghon focus and Hilar lymph node involvement

Question 24

what symptoms are seen in Chronic state Pulmonary tuberculosis?

Answer 24

Fibrosis, scaring

Calcification

Persist for life

Show up as radio-opaque nodules

Question 25

identify?

Answer 25

ghon complex

Question 26

identify

Answer 26

ghon focus

Question 27

what is secondary TB?

Answer 27

• 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)

Question 28

Clinical findings of secondary TB?

Answer 28

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

Question 29

what is Miliary Tuberculosis?

Answer 29

• 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*

Question 30

what are the complications of miliary TB?

Answer 30

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

Question 31

what is the skin test for M tuberculosis?

Answer 31

Mantoux tuberculin test

• CMI response to PPD

Question 32

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

Answer 32

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

Question 33

how is TB treated?

Answer 33

Isoniazid (Mycolic acid)

Rifampin (RNA Pol)

Pyrazinamide (cell wall)

Ethambutol (membrane)

Question 34

how do you treat multi-drug resistant TB?

Answer 34

Pyrazinamide

Ethambutol

Question 35

what vaccine is used to prevent TB?

Answer 35

BCG Vaccine (Bacillus Calmette-Guérin)