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Infectious Disease 2 > Mycobacterial Infections > Flashcards

Mycobacterial Infections Flashcards

1
Q

Cough classifications

-acute, subacute, chronic

A

acute: occurs for less than 3 weeks and is most commonly d/t acute respiratory tract infection
subacute: present for longer than 3 weeks but less than 8weeks
chronic: more than 8 weeks.

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2
Q

What are the 3 types of mycobacteria?

A
  • M. Tuberculosis
  • M. Leprae
  • Atypical and Nontubercular Mycobacterium
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3
Q

Tuberculosis is characterized by what?

A

-inflammatory inflitrations, formation of tubercles, caeseations (cheese), necrosis, abscesses, fibrosis, and calcification

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4
Q

Why do we use Acid Fast Bacilli stain for Tuberculosis?

A

-bacterial wall is different, it has a single wall that contains mycotic acid that takes up the Ziehl-Neelsen stain.

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5
Q

What is the greatest risk factor known for reactivating latent tb?

A

HIV

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6
Q

Inhalation and deposition of Tuberculosis in the lungs leads to one of four possible outcomes; what are these?

A
  • immediate clearance of the organism
  • chronic or LATENT infection
  • rapid progressive disease
  • active disease many years (2+) after the infection (reactivation disease)
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7
Q

Chronic or LATENT infection:

  • +/- PPD?
  • symptomatic?
  • CXR?
  • is this person infected?
A

+ PPD

  • asymptomatic
  • clear CXR
  • yes, infected but not infectious.
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8
Q

Primary TB disease

-pathogenesis

A

-small bacilli* carried in droplets small enough to reach alveolar space.

  • if hose system fails clearing… 1.) bacilli proliferate inside alveolar mfs and kill the cells. 2.) formation of nodular granulomatous structure called the tubercle or Gohn Focus*
  • *if the bacterial replication is not controlled, the tubercle enlarges and the bacilli enter the local draining lymph nodes leading to lymphadenopathy.
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9
Q

What is the Ghon complex?

A

-an inflamm nodule in the pulmonary parenchyma with an accompanying hilar adenopathy, in line with lymphatic drainage from that pulmonary segment.

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10
Q

If bacterial replication is controlled within the initial inflamm tubercle, TB is said to be in what stage?

A

-chronic or latent infection, patient will not develop primary disease.

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11
Q

What is Symptomatic Primary Disease?

A

-when the pt develops active disease within the first 1-3years after infection.

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12
Q

TB sx

A
  • appetite loss, fatigue
  • chest pain, hemoptysis, productive prolonged cough
  • night sweats, pallor
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13
Q

Patient has asymptomatic primary infection, their cell-mediated immunity contained the infection, and it remains dormant for years. Something goes awry in the host and recurrence ensues…Oh my! what type of TB is this?

A
  • secondary or reactivation TB

* basically immunosuppression leads to reactivation, may be d/t HIV/AIDS, DM, corticosteroid use.

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14
Q

In contrast to primary disease, the disease process in reactivation TB tends to be…

A

localized, there is little regional lymph node involvement and the lesion usually occurs at the lung apices.

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15
Q

Secondary/reactivation TB sx?

A
  • cough, hemoptysis
  • persistent fever/night sweats
  • weight loss
  • malaise
  • adenopathy
  • pleuritic chest pain
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16
Q

What is a Rasmussen Aneurysm?

A

weakening of the pulmonary artery wall from adjacent cavitary TB.

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17
Q

What is Miliary TB? When does this occur?

A

progressive, widely disseminated hematogenous TB.

-if bacterial growth continues to remain unchecked the bacilli may spread hematogenously to produce disseminated TB.

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18
Q

Sx of Miliary TB?

A
  • Acute: high fever, night sweats, resp distress, septic shock, multiorgan failure
  • acute tends to be in young
  • Chronic: fever, anorexia, weight loss
  • particularly in the elderly
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19
Q

Extrapulmonary TB Manifestations

A
  • pleural/pericardial effusions (TB pleurisy)
  • lymph node infection (scrofula=TB lymphadenitis of the neck)
  • skeletal
  • joints (Potts disease; TB of the spine)
  • CNS (meningitis)
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20
Q

Most persons diagnosed with TB are begun on specific treatment before the dx is confirmed by the lab, why do you think this is true?

A

-so they dont infect others, but MOSTLY because it takes a long time to confirm.

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21
Q

What is significant finding in positive PPD test?

A

-induration!!!! not the erythema.

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22
Q

What can you say about a person who has a positive PPD?

A

Positive PPD test does NOT by itself prove the presence of ACTIVE disease but DOES indicate that infection has occurred.

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23
Q

How do we test for TB?

A
  • Tuberculin skin testing
  • Acid Fast Bacilli Staining
  • Mycobacterium Culturing
  • others
24
Q

What is the most sensitive screening test for TB?

A

-Tuberculin Skin Test

25
Q

What is the primary use for PPD testing?

-How is PPD testing done?

A

-used for detection of Latent TB infection

  • ID injection, visible wheal present.
  • subQ admin will result in false-negative test if the patient in fact has been infected by TB)
26
Q

What is the time frame in reading a Tuberculin Skin test?

A

-must be read in 48-72hrs, test is read by the diameter of induration.

27
Q

What are some indications for Tuberculin Skin Testing?

A
  • HIV infection
  • ongoing close contact with cases of active TB (healthcare workers, prison gaurds, mycobacterial lab personnel)
  • presence of medical condition that increase risk of Active TB. (DM, steroids, alcoholism)
  • medically underserved, low income (homeless, injection drug users)
  • Residence in long-term care facility
  • single potential exposure to TB (family member)
  • incidental finding of fibrotic lung lesion
  • immigrants and refugees from countries w/ high prevalence of TB.
28
Q

What is the time interval from primary infection to TB skin test conversion?

A

-mean of 6weeks, this means it may take up to 6weeks after initial infection of TB to show up on Tuberculin Skin Test. You may have false negative result if done too early.

29
Q

Sources of false-negative tests

A
  • inadequate nutrition
  • anergy
  • concurrent viral infection
  • corticosteroid therapy.
30
Q

Guidlines for determining Positive PPD

A
  • induration > 5mm in HIV persons, recent contact of TB case, fibrotic changes on CXR with old TB, pt w/ organ transplants and other immunosuppressed pts.
  • induration >10mm in recent arrivals from high prevalence countries, injection drug users, residents and employees of prisons jails nursing homes and other health care facilities, those with high risk clinical conditions (DM, chronic renal failure), children 15mm for person with no risk factors for TB
  • induration 3-19mm several months after BCG (Bacille Calmette-Guerin) Vaccine.
31
Q

When active disease suspected there should be examination of sputum for acid-fast bacilli staining and mycobacterium culturing, True or false? Why?

A

-True. Sputum evaluation is the GOLD STANDARD for determining if the pt has TB or not.

32
Q

Acid Fast Bacilli Staining, how does this help in dx?

A

-the cell envelope of Mycobacterium distinguishes them from other organisms. There is no true outer membrane. The envelope is composed of mycolic acid

33
Q

What are the two versions of Acid Fast Bacilli Staining?

A
  • fluorochrome staining

- Ziehl-Neelsen

34
Q

What is one distinguishing factor in mycobacterium culturing?

How do you culture it, what type of media?

A

-its slow growth rate!

  • solid media
  • -lowenstein-Jensen or Middlebrook
  • -8weeks or longer for growth
  • liquid media
  • -more rapid growth and can detect growth of mycobacteria in clinical sample in as few as seven days.
35
Q

What is whole-blood intergeron-gamma assay?

-AKA?

A
  • screening test for asymptomatic disease (99% accurate)
  • T cells of individuals previously sensitized with Tb ag will produce interferon-gamma when they reencounter mycobacterial ags.
36
Q

What are soem advantages of Whole-blood interferon gamma assay over Tuberculin Skin testing?

A
  • subject to less testing error
  • less reader bias
  • can be accomplished after single visit
  • ma not be as likely to be positive after BCG vaccine
  • the RD1 ags used in this test are not shared with most non-tuberculous mycobacteria.
37
Q

What test can produce results within two to seven hours after sputum processing and is generally recommended on all AFB smear-positive respiratory specimens?

A

-Rapid Nucleic Acid Assay

38
Q

What is the consistent theme with several antitubercular drugs?

A

Watch the liver!

39
Q

Is TB just a lung disease?

A

NO!

40
Q

Can you expect to see the drugs used in first line TB therapy used in other circumstances?

A

No. You may very very occasionally see Rifampin

41
Q

What are some reasons to use Interferon gamma testing?

A
  • convenient
  • less prone to error
  • more accurate in folks previously vaccinated with BCG
  • less likely to be confused with other forms of mycobacterium
42
Q

Why is obtaining sputum in one who may have active TB critical?

A

because susceptibility testing will guide treatment

43
Q

PPD is read by the diameter of what?

A

induration, not erythema!

44
Q

What are pts with latent TB treated with?

A

INH monotherapy for 9 months

45
Q

In what populations is TB prevalence highest among?

A

foreign born immigrants
low socioeconomic groups
HIV patients
Drug users

46
Q

What is DOT? Who can deliver DOT?

A

DOT is Directly observed therapy.

A trained health care worker (not family member) provides the prescribed TB drugs and watched the pt swallow every dose

47
Q

TB management
Why does it take time to eradicate with antibacterials?
What are the most important things to remember?

A

Mycobacterium are rod-shaped bacteria with lipid-rich cell walls and they grow slowly

  • drugs MUST be taken in appropriate doses
  • drugs MUST be taken regularly
  • therapy MUST continue for a sufficient period of time
48
Q

How is a latent infection managed?

A

-Generally 9 months of Isoniazid (INH) monotherapy

alternative for INH is rifampin PO daily for 4 months

49
Q

How is reactivatoin TB disease managed?

A
  • requires at least 2 effective drugs because of the increased incidence of drug resistance
  • several guidelines recommend that initial therapy of active TB include four drugs:
  • isoniazid (INH)
  • Rifampin (RIF)
  • Pyrazinaminde (PZA)
  • Ethambutol (EMB)
50
Q

Isoniazid (INH)
MOA
Watch for

A

MOA: covalently binds to and inhibits enzymes essential for the synthesis of mycolic acid
(mycolic acid is a key component of the cell wall)
-not very effective against other organisms

-never use alone as resistant organisms will rapidly occur

Watch for:

  • heptotoxicity, must monitor liver enzymes
  • most common SE is peripheral neuritis (paresthesias)
51
Q

Rifampin (RIF)
MOA
effective against
watch for

A

MOA: blocks transcription by interfering with the beta subunit of bacterial RNA polymerase

Has broader antimicrobial activity than INH
-effective against mycobacterium, many gram positive and gram negative organisms

watch for:

  • hepatotoxicity, liver enzymes
  • inducer of cytochrome P450 enzymes and therefore the pt may need higher dosage requirements for other drugs metabolized by this system
52
Q

Pyrazinamide (PZA)
MOA
watch for

A

MOA: unknown

-only seen in antitubercular combo packages

watch for:

  • hepatotoxicity!!
  • gout
53
Q

Ethambutol (EMB)
MOA
Watch for

A

MOA: inhibits an enzyme important for the synthesis of the mycobacterial arabinogalactan call wall

Watch for:
-Optic neuritis (which results in diminished visual acuity and loss of ability to discriminate between red and green)

54
Q

Alternative second-line drugs for TB

A
  • aminosalicylic acid
  • capreomycin
  • cycloserine
  • ethionamide
  • fluoroquinolones
  • macrolides
55
Q

Why is pt compliance an issue?

A

because although sx might be gone in 2 months, the pt must continue therapy for 6 months to 2 years after.

TB occurs with a higher incidence in pt populations with higher noncompliance.

plus resistance is an issue.

Infectious Disease 2 (9 decks)

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