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PoD Test 2 > Mycobacteria > Flashcards

Mycobacteria Flashcards

1
Q

Describe mycobacteria.

A

Obligate aerobic G+ rod

Infections caused by aerosol droplet

Waxes in cell wall

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2
Q

What is primary tuberculosis?

A

TV caused by inhalation of aerosolized Mycobacterium spp including M. tuberculosis

Initial exposure causes primarty TB eith the formation of focal caseating necrosis in lower lung and hilar lymph nodes

Generally asymptomatic and PPD positive

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3
Q

What are two major risk factors for secondary TB due to reactivation?

A

Aging and HIV

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4
Q

What is the pathogenesis of secondary TB due to reactivation?

A

Occurs at apex of lung and can spread to any tissue

Forms cavitary foci of caseous necrosis; may also lead to miliary pulmonary TB or TB pronchopneymonia

Fevers and night sweats, cough with hemotypsis

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5
Q

Describe the cell envelope of mycobacteria

A

No outer membrane - so more closely related to G+

PG layer not as thick

Unique lipid composition

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6
Q

Why are the mycolic acids and lipids important?

A

Both structural components and virulence factors

Activates or suppresses the immune responses

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7
Q

What are the two subtypes of granuloma?

A

Noncaseating

Necrotizing or caseating

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8
Q

Describe TST application.

A

Tuberculin: Purified Protein Derivative (PPD)

Intradermal placement, 0.1 ml of tuberculin

Injection should produce a pale elevation of the skin 6-10mm

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9
Q

How is TST interpreted?

A

Two factors: Measurement and risk of progrression to active TB disease

The higher the risk for progressing to active TB, the lower the measurement cutoff for positive

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10
Q

What is an alternative test to PPD?

A

Interferon-Gamma Release Assay

Blood test that measures the amount of IFN-y produced by T cells exposed to Mtb antigens

IGRAs use peptides from Mtb antigens that are missing in BCG to stimulate T cells

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11
Q

How do you test for active TB disease?

A

Gold-standard is culture, but slow growth

AFB sputum smear can provide early indication of active TB

Tissue samples for extra-pulmonary disease

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12
Q

What is the best treatment for TB?

A

Isoniazid

Inhibits enzyme important for producing mycolic acids in the cell wall

Rapid killing for bacteria that are metabolically active, slower for non-dividing

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13
Q

What are treatments for besides Isoniazid?

A

Rifampin - RNA pol inhibitor

Pyrazinamide - active disease

Ethambutol - treat active disease when INH resistance is suspected

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14
Q

What is the Treatment regimen for pulmonary TB?

A

3 or 4 drugs for two months followed by 2 drugs for four months

RIF, INH, PZA and EMB for two months

INH and RIF for 4 months

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15
Q

What demographic is particularly susceptible to TB?

A

HIV-positive

Leading killer

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16
Q

What is Mycobacterium avium-intracellulare Complex?

A

Acid-Fast bacilli found in macrophages, grows faster than MTB

Second to TB in significance and frequency

Causes systemic infections in HIV patients

17
Q

What is M. kansasii?

A

Causes cavitary pulmonary disease, cervical lymphadenitis and skin infections

PPD positive, resembles tuberculosis

Prolonged chemotherapy with isoniazid, rifampin and ethambutanol

18
Q

What is M. leprae?

A

Rare in US

Infection manifested by two presentaitons:

Tuberculoid leprosy-miler and self-limiting disease (CMI)

Lepratomous leprosy-severest form of leprosy (NO CMI)

19
Q

What is Tuberucloid leprosy?

A

Red blotchy leasions with anesthetic areas

CMI - Th1

Low infectivity

20
Q

What is Lepromatous Leprosy?

A

Multibacillary, unimpeded bacterial growth

Skin lesions are diffuse, extensive, depiliated with extensive tissue destruction

CMI deficient, Th2 response

High infectivity

21
Q

What is the treatment for leprosy?

A

Tuberculoid - Dapsone and rifampin

Lepromatous: Dapsone, rifampin, and clofazimine

22
Q

What is the MoA for Dapsone?

A

Inhibits dihydropteroate synthetase

Disrupts folic acid pathways

23
Q

What is the result of an IL-2 receptor deficiency?

A

Weak Th1 response and low levels of IFN-y

Increased susceptibility:

Disseminated Salmonella, non tuberculosis mycobacteria, BCG after vaccine

PoD Test 2 (23 decks)

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