Mycobacterium

Question 1

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

Answer 1

Mycolic acid

Question 2

M.tuberculosis is an obligate _______ that replicates within ________

Answer 2

Aerobe; macrophages

Question 3

Dye used for detection of TB

Answer 3

Carbol fuschin dye

Question 4

Virulence factors associated with TB

Answer 4

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

Question 5

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

Answer 5

Primary — middle or lower lobes

Secondary — upper lobes

Question 6

Presentation of primary TB

Answer 6

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

Question 7

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

Reactivation is associated with the use of __________ inhibitors

Answer 7

Latent

TNF-alpha

Question 8

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

Answer 8

Miliary TB

Question 9

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

Answer 9

Pott disease [Tuberculous spondylitis]

Question 10

Vaccine that may cause positive result on PPD

Answer 10

Bacille Calmette-Guerin (BCG) vaccine

Question 11

Morphology of TB

Answer 11

Weakly gram + rod, non-motile, aerobic

Question 12

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

Answer 12

Fibrosis; calcification

Question 13

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

Answer 13

Primary progressive

Question 14

3 patterns of primary progressive TB

Answer 14

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)

Question 15

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

Answer 15

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

CXR: apical and posterior segment involvement, pulmonary cavitation present

Question 16

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

Answer 16

CXR

PPD skin test (Mantoux)

Morning sputum culture

Question 17

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?

Answer 17

Healthy individual >4 with low likelihood of true TB infection

Question 18

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?

Answer 18

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

Question 19

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?

Answer 19

HIV

Close contact with actively infected person

CXR with fibrotic changes consistent with TB

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

Question 20

Describe PPD skin test

Answer 20

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

Question 21

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

Answer 21

M.bovis

Question 22

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

Answer 22

Previous BCG vaccine

Infection w/ nontuberculosis mycobacterium

Incorrect administration of PPD

Incorrect interpretation

Question 23

What might cause false negatives on PPD?

Answer 23

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

Question 24

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

Answer 24

Type IV HSR — delayed (T cells)

Question 25

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 ```

Answer 25

C. Auramine-rhodamine stain Utilizes fluorescent microscopy — MOST SENSITIVE for AFB organisms!! [Ziehl-Neelson and Kinyoun are confirmatory AFB stains, more SPECIFIC for TB]

Question 26

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

Answer 26

Rifampin and INH

Question 27

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

Answer 27

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

Question 28

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

Answer 28

Interferon-gamma release assay (aka Quantiferon gold or T-spot) This will give more definitive result

Question 29

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

Answer 29

Ethambutol

Question 30

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

Answer 30

6 months; requires monitoring with sputum samples

Question 31

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 ```

Answer 31

B. Positive adenosine deaminase — indicative of TB

Question 32

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

Answer 32

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)

Question 33

____ = calcified primary focus with hilar lymphadenopathy on CXR _____ = calcified primary foci in peripheral lung tissue

Answer 33

Ranke Ghon

Question 34

General steps in management of active TB

Answer 34

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

Question 35

Drug therapy utilized in drug-resistant forms of TB

Answer 35

Streptomycin

Question 36

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

Answer 36

INH; 9

Question 37

Populations at highest risk for TB

Answer 37

``` Malnourished Homeless Overcrowded areas HIV/immunosuppressed Living in endemic areas ```

Question 38

Extrapulmonary manifestations of Tb

Answer 38

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)

Question 39

Morphology of mycobacterium kansasii

Answer 39

Acid fast bacillus Nonmotile

Question 40

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

Answer 40

False — it is picked up from the environment

Question 41

Patient populations in which you see mycobacterium kansasii

Answer 41

Older pts with underlying lung disease or long time smokers M>>W

Question 42

Endemic areas for mycobacterium kansasii

Answer 42

Midwest and southwest US

Question 43

Sx and CXR findings with mycobacterium kansasii

Answer 43

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

Question 44

Tx and prognosis of mycobacterium kansasii

Answer 44

Tx: Rifampin, INH, and ethambutol for at least 18 months Left untreated = 50% mortality