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Pulmonology > TB - Cross > Flashcards

TB - Cross Flashcards

1
Q

What type of stain is best used to detect mycobacterium tuberculosis?

A

Acid fast stain

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2
Q

What property of M. tuberculosis allows it to stain like it does?

A

Mycolic acid

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3
Q

What is mycolic acid and where is it found?

A

fatty acid found in the cell wall

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4
Q

Virulent strains are associated with what (think virulence factor)? Where does the name come from?

A

Cord factor, due to virulent strains growing in a cord-like pattern
Avirulent strains do not have cord factor

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5
Q

Cord factor MOA?

A

inhibits macrophage maturation and induces TNF-alpha release

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6
Q

Besides cord factor, what is another virulence factor important to M.tuberculosis? MOA?

A

Sulfatides (surface glycolipids) inhibit phagolysosomal fusion

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7
Q

Cell wall of mycobacterium has what 4 components?

A

Mycolic acids, glycolipids, arabinogalactans, free lipids

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8
Q

Risk factors predisposing to TB. List as many

A
  • prison (crowded conditions)
  • immigrant from high burden country
  • malnourished
  • alcoholism
  • poverty
  • debilitating illness
  • AIDS
  • Elderly
  • Certain disease: DM, Hodgkin lymphoma, CKD, malnutrition, immunosuppression; RA on TNF alpha antagonist
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9
Q

What is the critical mediator that allows macrophages to contain the infection?

A

IFN-gamma

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10
Q

Most important determinant of whether overt TB disease occurs?

A

Adequacy of cell mediated immunity

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11
Q

Pathogenesis. Initially, MTB enters what cells via what process?

A

Enters macrophages via phagocytosis

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12
Q

Pathogenesis. After MTB has entered macrophage via phagocytosis, what occurs?

A

It will inhibit the formation of the phagolysosome, allowing bacteria to replicate

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13
Q

Pathogenesis. After phagolysosome has been inhibited by TB, what cytokine is produced and what does it do?

A

After phagolysosome inhibited, IL-12 is produced, stimulating a T-helper response. IFN-gamma is then produced via Th1 cells, enabling macrophages to contain the infection (forming a granuloma)

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14
Q

Pathogenesis. Activated macrophages secrete what factors? What is there role?

A

Activated macrophages secrete TNF-alpha and cytokines that recruit more monocytes

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15
Q

Primary infection defined as?

A

Transmission from active case to susceptible host

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16
Q

Primary infections are asymptomatic or symptomatic?

A

asymptomatic, 95% of cases

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17
Q

Only evidence of primary infection is?

A

fibrocalcific nodule at site of infection

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18
Q

Secondary infection defined as?

A

When viable organisms remain dormant for years, reactivate to produce secondary infection (active disease)

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19
Q

Secondary infection usually involves what location of lungs? Why?

A

apices of lungs. MTB is an obligate aerobe and there is better O2 content at apex of lung

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20
Q

Cavitation occurs frequently in primary or secondary infection?

A

secondary

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21
Q

Erythema nodosum? Prognosis good or bad? Why? Is it specific for TB?

A

Indicative of good prognosis. Sign of good cell mediated immunity/ hypersensitivity response. Not specific for TB

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22
Q

What tests should be done to diagnose TB?
Which is the initial test?
List the time it takes for each one

A

Acid fast stain on sputum (initial test)
Lowenstein Jensen solid agar - 3-6 weeks
Culture in liquid media - 2 weeks
PCR or nucleic acid amplification - rapid

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23
Q

What test should NOT be done to diagnose TB

A

Culture on blood agar, it will not grow

24
Q

PCR or nucleic acid amplification better for smear positive or smear negative specimens?

A

Smear positive (initially sputum will come back smear positive or negative)

25
Q

What is the 1st line choice of antibiotics for TB?

A 
RIPE
Rifampin
Isoniazid
Pyrazinamide
Ethambutol
26
Q

Miliary/Disseminated TB requires RIPE treatment for how long?

A

9-12 months

27
Q

Miliary TB pathophysiology. What occurs?

A

TV invasion into bronchus or lymphatics causes spread of TB throughout the lungs (and potentially elsewhere in the body). Lungs specifically look like millet seeds on CXR, hence the name

28
Q

What subset of patients are at high risk for miliary TB?

A

HIV patients

29
Q

What other organs are commonly infected in military TB?

A

Kidneys, Liver, bone marrow, spleen

30
Q

What is the most common extra pulmonary site of miliary TB?

A

Kidneys

31
Q

Miliary TB spreading to vertebrae = ?

A

Pott Disease

32
Q

RA patients on antagonists of what cytokine are at increased risk for TB?

A

RA patients on TNF-alpha antagonists. If TNA-alpha not induced, granulomas won’t form and patient will have disseminated TB = death

33
Q

Once susceptibility is confirmed, which therapy from RIPE can be discontinued

A

Ethambutol

34
Q

Multidrug resistant TB is most commonly resistant to what drugs? What subset of patients are more likely to be MDR-TB patients?

A

Isoniazid and Rifampin, AIDS patients

35
Q

TB and HIV. What is a important risk factor?

A

Low CD4 count, can’t produce Th1 cells, no IL-12.

36
Q

TB and HIV. Sputum culture statistics?

A

Increased frequency of false negative sputum smears

37
Q

TB and HIV. Granuloma frequency?

A

Absence of granulomas in tissues

38
Q

TB and HIV. Compare cavitation/bronchial damage as compared to healthy non HIV patients.

A

HIV patients have reduced immune response, therefore decreased cavitation/bronchial damage and fewer acid fast bacilli in sputum

39
Q

Purified protein derivative (PPD) test can be false positive for MTB if?

A

Patient has been exposed to other mycobacterium (such as mycobacterium avium)

40
Q

What latent TB test is only specific to MTB?

A

IGRA - IFN gamma release assay

41
Q

Which latent TB test is the gold standard?

A

IGRA - IFN gamma release assay

42
Q

How can you get a false positive with the PPD test?

A

If patient has been immunized with BCG vaccine

43
Q

If patient has BCG vaccine or a non tuberculosis mycobacterium infection, what will happen to the IGRA?

A

Nothing, there are no false positives with BCG or NTB infections

44
Q

What is one case where the PPD and IGRA test can have a false negative? Why? What is this called?

A

HIV patients, can produce false negative due to lack of immune response, sometimes called anergy

45
Q

Whats is the treatment for latent TB?

A

Isoniazid for 9 months; Isoniazid and Rifapentine for 3 months

46
Q

If patient tests positive for Latent TB, what is your next step?

A

Make sure they do not have an active disease. Obtain a CXR and do a workup before you put them on medication for latent TB

47
Q

Bacillus Calmette-Guerin (BCG) vaccine used against TB contains a strain from which mycobacterial species?

A

Mycobacterium bovis

48
Q

BCG vaccine is limited in U.S to who?

A

young children in close contact with individuals with active TB and military personnel

49
Q

BCG vaccine is contraindicated in what patients?

A

Immunocompromised patients

50
Q

BCG vaccine is also used to treat what cancer?

A

Bladder cancer

51
Q

Adverse effect of Rifampin

A

Orange-red secretions (tears,urine, saliva) will stain contact lenses

52
Q

Toxicity associated with Rifampin

A

Hepatotoxicity

53
Q

Isoniazid associated with 2 types of toxicity based on what characteristic?

A

Slow acetylators of INH - neuropathy

Fast acetylators of INH - hepatotoxicity

54
Q

Pyrazinamide adverse effect?

A

hyperuricemia - leading to gout

55
Q

Ethambutol toxicity?

A

Ocular toxicity

Pulmonology (31 decks)

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