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Flashcards in Micro: Tuberculosis Deck (37)
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1
Q

Mycobacterium tuberculosis is extracellular or intracellular ?

A

Intracellular.

2
Q

What constituent of M.tuberculosis cell wall (yes there is a cell wall) makes a Gram stain unlikely ?

A

Mycolic acid !

3
Q

What protective purpose does mycolic acid serve ?

A

resistant to detergents and common antibiotics

Protects the cell from desiccation (does not dry out)

4
Q

What culture media will M.tuberculosis grow on ?

A

Lowenstein-Jensen Agar (gold standard for diagnosis but not practical due to long growth period)

5
Q

What diagnostic stain is used to identify M.tuberculosis ?

A

Acid Fast (Ziehl Nelson stain)

6
Q

What is Cord Factor ?

A

surface glycolipid which blocks macrophage activation by IFN-γ, induces secretion of TNFα and causes Mycobacterium tuberculosis to form cords in vitro

Allows for anti-microbial resistance to many antibiotics.

7
Q

What causes tissue necrosis in TB ?

A

Host immune response

8
Q

Describe the signs and symptoms associated with TB

A

Mild fever , chest pain, cough (productive and often bloody), Fatigue, malaise, weight loss and sweating.

9
Q

Where is M.tuberculosis endemic to ?

A

Southeast asia
Sub-saharan africa
Eastern Europe

10
Q

Primary tuberculosis

A

Initial cause of tuberculosis disease

11
Q

Secondary tuberculosis

A

reactivation of a latent infection

12
Q

Disseminated tuberculosis

A

involves many (milliary spread)

13
Q

What cells does m.tuberculosis infect intracellularly ?

A

Alveolar macrophages (much like legionella)

14
Q

Activation and recruitment of alveolar macrophages leads to the formation of …

A

Tubercle (Granuloma)

15
Q

Caseous lesion

A

Cheese like interior to a granuloma

16
Q

Ghon complex

A

Calcified casesou lesion (show up in chest x rays well)

17
Q

Tuberculous cavities

A

Tubercle that has liquified and formed and air-filled cavity in which bacteria can spread from

Reactivation tuberculosis (secondary)
Aspergillus likes these cavities !
18
Q

Screening

A

Tuberculin (Mantoux Test)

19
Q

+ Tuberculin. Whats next ?

A

Chest X-ray for signs of tubercles

Microscopy of sputum (Acid Fast staining of sputum)

20
Q

3rd step is TB diagnosis (not entirely necessary)

A

Culture on Lowenstein Jensen.

Specific but extremely slow .

21
Q

What are the 4 main drugs used in treatment of tuberculosis ?

A

Isoniazid
Rifampin
Ethambutol
Pyrazinamide

22
Q

Describe the “Preferred” Regimen for treating TB

A

Initial: Daily INH, RIF, PZA and EMB for 56 doses (8 weeks)

COntinuation: Daily INH and RIF for 126 doses (18 weeks)

23
Q

Describe the Alternative Regimen for TB treatment

A

Intial : Daily INH, RIF, PZA and EMB for 14 dosed (2 weeks) the twice weekly for 12 doses (6 weeks)

Continuation: Twice weekly INH and RIF for 36 doses (18 weeks)

24
Q

MDR-TB

A

Multi-drug resistant TB –> Resistant to Isoniazid and Rifampin ! (Uh Oh)

25
Q

XDR-TB

A

Extremely drug resistant TB–> Resistant to isoniazid , rifampin and at least one of the other two (ethambutol or pyrazinamide)

26
Q

DOTS

A

Directly Observed Treatment Short Course

27
Q

Why do we not give out the Bacille Calmette Guerin vaccine in the US ?

A

We have such a low occurrence of TB and the vaccine would render the Mantoux test ineffective for screening.

BCG is a mycobacterium bovis strain.

28
Q

Describe Micobacterium Avium Complex

A

Mixture of : Mycobacterium Avium and Mycobacterium Intracellulare

Weakly G+
Acid Fast Aerobic Rods (Mycolic acid in cell wall)

29
Q

Who typically contracts MAC ?

A

Immunocomrpromised patients

Chronic Pulmonary disease.

30
Q

Primary MAC

A

Similar to primary TB

31
Q

Secondary MAC

A

Dissemination to all organs and blood stream !

32
Q

Who typically get s 2nd MAC ?

A

AIDS patients with low CD4+ T-Cell counts ( <50 Cells/ml)

33
Q

How do you prevent MAC infection in AIDS patients ?

A

Constant prophylaxis with
Clarithromycin
Azithromycin

34
Q

Describe the lab diagnostics of Nocardia

A

Gram +, Aerobic
Weakly Acid fast
Branching Filaments (Branched long Rods)
Normally found in the soil

CUlture: BLood or Chocolate Agar

35
Q

Who is at risk for nocardiosis ?

A

Immunocompromised

Renal transplants

36
Q

Where does nocardia spread to after forming lung abscesses ?

A

Brain and kidney (renal patients at increased risk)

37
Q

TOC for Nocardia

A

IV Trimethoprim-sulfonhexamide (Bactrim)

Linezolid