Mycobacterium

Question 1

What is a disease caused by mycobacteria?

Answer 1

TB

Question 2

What is the rate of growth of M. tuberculosis? What does it invade? What is its oxygen requirement?

Answer 2

Slow growing
Macrophages
Obligate aerobe

Question 3

What are two forms of TB?

Answer 3

primary and secondary

Question 4

Describe primary TB

Answer 4

mild
starts from the lung
formation of granulomas, followed by caseation

Question 5

Describe secondary TB

Answer 5

caused by reactivation of dormant organism.

Delayed-type hypersinsitivity reaction to the reactivated org

Question 6

How does primary TB differ in immunocompromised individuals?

Answer 6

the granuloma/caseation proceeds to miliary TB with dissemination to other body sites, bone marrow, spleen, kidney and CNS

Question 7

How does the x-ray differ in two forms of TB?

Answer 7

primary - outline, macrophage

secondary - apex, mid lung

Question 8

What is the Ghon complex?

Answer 8

Granuloma caused by multinucleated cells, fused macrophages, T cell, fibroblast –> caseous necrosis

Question 9

What is Miliary TB? What type of patients is this seen in?

Answer 9

White nodules, smaller than granulomas. Seen in HIV patients

Question 10

How are MTB infections transmitted?

Answer 10

aerosols

Question 11

What is significant about MTB cell wall? What does it do?

Answer 11

Waxes in cell wall. provides resistance to drying and chemicals, germicides
affects permeability of cell - nutrients can’t get in - slow growth

Question 12

What is used to ID Mycobacteria?

Answer 12

Acid fast stain

Question 13

What are two main chemicals used in acid fast stain?

Answer 13

Carbolfuchsin

Acid alcohol

Question 14

What color is Mycobacteria seen as after acid fast stain? What is the reason for that?

Answer 14

Bright red because of the wax that does not get destained with acid alcohol

Question 15

What is a medium used to ID M. tuberculosis?

Answer 15

Lowenstein-Jensen

Middlebrook 7H10

Question 16

What component of the acidic wax is toxic?

Answer 16

Mycolic acid (beta-hydroxy fatty acid linked to murein)

Question 17

Where does MTB grow?

Answer 17

Macrophages and monocytes

Question 18

What two things allow MTV to escape phagosomes?

Answer 18

• prevents acidification via NH4 production –> no phagosome/lysosome fusion/acidification
• Hemolysin

Question 19

What cytokine provoked by cell wall components cause lung damage?

Answer 19

TNF-a

Question 20

TB is associated which group of immuno compromised patients?

Answer 20

AIDS

Question 21

Patients with AIDS and TB are more likely to develop what?

Answer 21

extrapulmonary disease, lymph nodes, genitourinary CNS

Question 22

What is the consequence of reduced CD4+ T cell in AIDS/TB patients? Explain the process

Answer 22

no macrophage activation

Macs release IL-12 –> Th1 recruited –> Th1 releases IFN-g –> Mac activation

Without Th1, the activation cannot occur

Question 23

What specific infection are patients with AIDS susceptible to?

Answer 23

MAI

Question 24

What is the current therapy for TB/AIDs a combination of ?

Answer 24

Macrolides
Rifabutin
Ethambutol
Clofazimine
FQN

Question 25

What are the four Anti-TB drugs? How long?

Answer 25

Isoniazid (INH) * Rifampin Streptomycin Ethambutol 6 months

Question 26

Treatment for TB

Answer 26

Anti-TB drugs Prophylaxis Vaccine

Question 27

What is MAI?

Answer 27

faster growing acid-fast bacilli found in macrophages

Question 28

How does co-infection of MAI occur in AIDS patients?

Answer 28

Fruit in GI of immunosuppresant patients can spread -- systemic infection

Question 29

What is seen in cultures with MAI?

Answer 29

MAC (MAI complex) | - wax, miliary, macs

Question 30

Can M. leprae be grown in lab medium?

Answer 30

No

Question 31

How is M. leprae confirmed?

Answer 31

skin test reactivity to lepromin | presence of acid-fast bacilli in skin lesions

Question 32

What are the two different presentations of M. Leprae?

Answer 32

- Tuberculoid leprosy: milder, self-limiting disease (cell mediated) - Lepratomous leprosy: severest form (not cell mediated)

Question 33

Which T cell is involved in Tuberculoid leprosy? what is the infectivity?

Answer 33

Th1 | low infectivity

Question 34

What T cell response is seen in Lepromatous Leprosy? what is the infectivity?

Answer 34

Th2 | High infectivity

Question 35

How does Lepromatous leprosy differ from Tuberculoid in terms of immunity?

Answer 35

Lepromatous is Autoimmune

Question 36

Due to lack of Th1 response, Lepromatous leprosy is ______ to lepromin.

Answer 36

nonreactive

Question 37

What is analogous to miliary TB?

Answer 37

Lepromatous leprosy

Question 38

What is the effect of Lepromatous leprosy?

Answer 38

extensive tissue destruction | CNS damage - schwann cells

Question 39

Treatment for M. leprae | how long?

Answer 39

Dapsone rifampin clofazimine minimum of 2 years

Question 40

Why is M. kansasii atypical?

Answer 40

yellow pigmented in presence of light

Question 41

Who can have M. kansasii?

Answer 41

HIV patients with CD4 count less than 200 cells/ml

Question 42

How does M. kansasii present?

Answer 42

PPD positive | resembles tuberculosis

Question 43

Treatment of M. kasasii

Answer 43

chemotherapy with isoniazid, rifampin, ethambutanol

Question 44

What is the most significant point made in lecture about mycobacterium?

Answer 44

HIV co-infection