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Respiratory Medicine Exam II > Mycobacterium > Flashcards

Mycobacterium Flashcards

1
Q

Mycobacterium tuberculosis is acid-fast due to high ________ content in its cell membrane

A

Mycolic acid

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2
Q

M.tuberculosis is an obligate _______ that replicates within ________

A

Aerobe; macrophages

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3
Q

Dye used for detection of TB

A

Carbol fuschin dye

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4
Q

Virulence factors associated with TB

A

Cord factor — membrane glycolipid, protects from host responses; release cachectin —> weight loss

Sulfatides — sulfolipids that prevent phagolysosome fusion (protect from lysosomal hydrolases, allow intracellular survival)

Siderophore — iron acquisition

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5
Q

What part of the lung is affected by primary vs. secondary TB?

A

Primary — middle or lower lobes

Secondary — upper lobes

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6
Q

Presentation of primary TB

A

Typically affects middle or lower lung lobes

Most common sx = low grade fever (usually no other sx); CXR shows hilar LAD, can develop pleural effusions

Caseating granulomas characterized by central necrotic zone, walled off by macrophages and lymphocytes; Ghon complex

Usually resolves by fibrosis of lung tissue

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7
Q

_____ TB occurs when dormant bacteria are contained within walled off foci

Reactivation is associated with the use of __________ inhibitors

A

Latent

TNF-alpha

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8
Q

Type of TB characterized by diffuse hematogenous spread to multiple organs; may present with cough, hemoptysis, night sweats, etc., and is potentially fatal

A

Miliary TB

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9
Q

Disease resulting from progressive primary OR reactivation/secondary TB involving infection of the vertebral column (typically lower thoracic/upper lumbar)

A

Pott disease [Tuberculous spondylitis]

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10
Q

Vaccine that may cause positive result on PPD

A

Bacille Calmette-Guerin (BCG) vaccine

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11
Q

Morphology of TB

A

Weakly gram + rod, non-motile, aerobic

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12
Q

Typically after an individual is infected with M.tuberculosis, there is healing by _____ and/or ______

A

Fibrosis; calcification

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13
Q

Typically after an individual is infected with M.tuberculosis, there is healing by fibrosis and/or calcification.

If this does NOT occur, the patient will have _____ _____ TB

A

Primary progressive

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14
Q

3 patterns of primary progressive TB

A

Primary caseous pneumonia — Gohn complex expands to entire lobe or segment, caseating necrosis, consolidated appearance

Tuberculosis bronchopneumonia — secondary to bronchogenic spread to entire lung parenchyma, patchy foci

Miliary tuberculosis — secondary to hematogenous spread, multiple nodules, millet seed appearance, spread across entire affected organ (liver, kidneys, meninges, spleen)

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15
Q

Sx and CXR findings associated with secondary TB (aka reactivation TB)

A

Insidious sx: fevers, chills, cough (+/- hemoptysis), weight loss, etc.

CXR: apical and posterior segment involvement, pulmonary cavitation present

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16
Q

If you suspect a patient is presenting with secondary TB, what are 3 tests that should be done next?

A

CXR

PPD skin test (Mantoux)

Morning sputum culture

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17
Q

PPD reaction sizes are categorized at >5 mm induration, >10 mm induration, >15 mm induration, and anergy.

In what situation(s) would a >15 mm induration be considered positive?

A

Healthy individual >4 with low likelihood of true TB infection

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18
Q

PPD reaction sizes are categorized at >5 mm induration, >10 mm induration, >15 mm induration, and anergy.

In what situation(s) would a >10 mm induration be considered positive?

A

Pts with clinical conditions that INCREASE risk of reactivation — silicosis, DM, chronic renal failure w/dialysis, malignancies (leukemia, lymphoma, lung, head/neck), malnourished, IV drug abuse

Children <4

From country with high prevalence

Residents/employees in high risk setting — jail, healthcare facilities, mycobacterium labs, homeless shelters

19
Q

PPD reaction sizes are categorized at >5 mm induration, >10 mm induration, >15 mm induration, and anergy.

In what situation(s) would a >5 mm induration be considered positive?

A

HIV

Close contact with actively infected person

CXR with fibrotic changes consistent with TB

Immunosuppression (TNF-a inhibitors, chronic glucocorticoids, chemotherapy, organ transplant)

20
Q

Describe PPD skin test

A

Aka Mantoux tuberculin skin test (TST)

Intradermal injection read within 48-72 hours

Made from PURIFIED PROTEIN of M.tuberculosis — will not cause infection, will illicit a reaction if previous exposure

21
Q

The BCG vaccination is made from ______; it is given to kids and individuals exposed to TB or those that live in high prevalence area

A

M.bovis

22
Q

What are some things that might cause false positive PPD test?

A

Previous BCG vaccine

Infection w/ nontuberculosis mycobacterium

Incorrect administration of PPD

Incorrect interpretation

23
Q

What might cause false negatives on PPD?

A

Anergy

Recent TB exposure (not enough time to generate response)

Very old TB

Age <6 months

Recent live virus vaccination or infection with virus (measles, chicken pox)

Overwhelming TB infection

24
Q

A PPD skin test is an example of what type of hypersensitivity reaction?

A

Type IV HSR — delayed (T cells)

25
Q

Which of the following is the initial staining that should occur to SCREEN for M.tuberculosis?

A. Ziehl-Neelsen stain
B. Methenamine stain
C. Auramine-rhodamine stain
D. India ink stain
E. Gram stain
A

C. Auramine-rhodamine stain

Utilizes fluorescent microscopy — MOST SENSITIVE for AFB organisms!!

[Ziehl-Neelson and Kinyoun are confirmatory AFB stains, more SPECIFIC for TB]

26
Q

The benefit of nucleic acid amplification testing (NAAT) is to detect resistance to which drug(s) in the mainstay TB treatment regimen?

A

Rifampin and INH

27
Q

What type of isolation room should pts be admitted to when they have confirmed active TB?

A

One with negative-pressure ventilation — minimizes risk of aerosolized transmission throughout hospital

28
Q

A pt with a hx of receiving the BCG vaccination returns with a positive PPD skin test. What is the next step?

A

Interferon-gamma release assay (aka Quantiferon gold or T-spot)

This will give more definitive result

29
Q

Which of the TB medications may cause the adverse effects of blurry vision, seeing “flashing lights”, diminished peripheral vision, decreased color vision, etc.?

A

Ethambutol

30
Q

A patient diagnosed with active tuberculosis (latent) can expect 4-drug regimen for what duration of time?

A

6 months; requires monitoring with sputum samples

31
Q

A TB patient presents with pleural effusions; what is the most likely finding on aspirate of the fluid?

A. Elevated amylase
B. Positive adenosine deaminase
C. High triglycerides
D. >100,000 RBC/mcL
E. Clear, translucent fluid
A

B. Positive adenosine deaminase — indicative of TB

32
Q

What general tests/labs/etc are included in the workup for M.tuberculosis?

A

CXR

PPD (mantoux)

NAAT-TB and NAAT-R

Sputum culture

Interferon-gamma release assay (for BCG vaccinated individuals and positive PPD with low likelihood of TB)

33
Q

____ = calcified primary focus with hilar lymphadenopathy on CXR

_____ = calcified primary foci in peripheral lung tissue

A

Ranke

Ghon

34
Q

General steps in management of active TB

A

4 drug therapy: INH, rifampin, pyrazinamide, ethambutol

Treat for at least 6 months; follow with sputum cultures, CBC, CMP

DOT preferred

If admitting — place in negative pressure isolation room

35
Q

Drug therapy utilized in drug-resistant forms of TB

A

Streptomycin

36
Q

In latent TB, ______ is given for _____ month(s)

A

INH; 9

37
Q

Populations at highest risk for TB

A 
Malnourished
Homeless
Overcrowded areas
HIV/immunosuppressed
Living in endemic areas
38
Q

Extrapulmonary manifestations of Tb

A

Most common is lymphadenitis (scrofula)

Pleural effusions (generally seen in primary progressive TB)

Meningitis

Tuberculous spondylitis (Pott disease)

Intestinal TB — secondary to contaminated milk ingestion (think M.bovis)

39
Q

Morphology of mycobacterium kansasii

A

Acid fast bacillus

Nonmotile

40
Q

T/F: mycobacterium kansasii is spread via person-person contact

A

False — it is picked up from the environment

41
Q

Patient populations in which you see mycobacterium kansasii

A

Older pts with underlying lung disease or long time smokers

M»W

42
Q

Endemic areas for mycobacterium kansasii

A

Midwest and southwest US

43
Q

Sx and CXR findings with mycobacterium kansasii

A

Sx: very similar to TB, but follows longer course; fevers can be present 17% of the time

CXR: Older smokers (cavitary lesion in apex), women with chronic cough (bronchiectasis in mid-lung zone), pneumonitis hypersensitivity s/p exposure

44
Q

Tx and prognosis of mycobacterium kansasii

A

Tx: Rifampin, INH, and ethambutol for at least 18 months

Left untreated = 50% mortality

Respiratory Medicine Exam II (11 decks)

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