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Microbiology Lecture Slides > Myobacterium I > Flashcards

Myobacterium I Flashcards

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1
Q

Thin, rod shaped (0.2 to 0.4 x 10 um)

-non-motile

A

Myobacterium

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2
Q

What is the aerobic classification of myobacterium?

A

Obligate anaerobes

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3
Q

Cell wall contains N-glucolylmuramic acid (instead of N-acetylmuramic acid) and has a very high lipid content

A

Myobacterium

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4
Q

Has a slow growing doubling time. Anywhere from 30 h to 4-8 weeks

A

Myobacterium

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5
Q

What are the four myobacterial-specific features of the myobacterial outer wall?

A
  1. ) Acyl lipids
  2. ) Mycolate
  3. ) Arabinogalactan
  4. ) Lipoarabinomannan (LAM)
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6
Q

The lipid-rich myobacterial wall is highly impermeable. It shows up in

A

Acid fast stain

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7
Q

Effective therapeutic target for anti-TBs

A

Lipid-rich wall

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8
Q

What are the two faces of myobacterium on Gram stain sputum?

A

Ghosts (complete lack of staining) and Beaded GPR

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9
Q

Binding of Carbol Fuchsin to mycolic acid is resistant to destrain by acid-alcohol; tissue and non-acid-fast organisms are counterstained with

A

Methylene blue

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10
Q

Fluorochromes auramine O (green) and auramine-Rhodamine (orange) bind

A

Mycolic acid

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11
Q

What is more sensitive fluorochrome stain or ZN stain?

A

Fluorochrome stain

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12
Q

M. tuberculosis, M. bovis, M. bovis BCG, M. africanum, M. microti, and M. canettii make up the

A

Mtb complex

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13
Q

All components of the complex cause TB so species level ID is not necessary for routine clinical purposes

A

Mtb complex

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14
Q

What type of colonies does the Mtb complex form?

A

Non-pigmented colonies

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15
Q

1/3 of the world’s population is infected

-8 million new cases and 2.9 million deaths annually in the world

A

Mtb disease

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16
Q

TB is spread person to person through the air via

A

Droplet nuclei

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17
Q

Mtb may be expelled when an infectious person:

A

Coughs, sneezes, speaks, or sings

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18
Q

Occurs when another person inhales droplet nuclei and the bacilli reach the alveoli of the lungs

A

Mtb transmission

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19
Q

Approximately 5% of Mtb infected patients develop transmissable

A

Pulmonary disease

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20
Q

Chronic clinical course with delays in diagnosis and treatment contribute to

A

Mtb transmission

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21
Q

M. bovis BCG is less transmissible than

A

M. tuberculosis

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22
Q

Droplet nuclei containing tubercle bacilli are inhaled, enter the lungs, and travel to

A

Alveoli

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23
Q

Then, tubercle bacilli multiply in

A

Alveolar macrophages

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24
Q

Within 2 to 8 weeks, cell mediated immunity develops and activated macrophages surround the tubercle bacilli; these cells form a

-Keeps the bacilli contained and under control

A

Barrier Shell (granuloma)

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25
Q

The presence of slender acid-fast positive, slightly curved and beaded bacilli, is suggestive of

A

Myobacteria

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26
Q

In most individuals, TB infection remains latent due to

A

Immunity (delayed type hypersensitivity)

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27
Q

Can be demonstrated by positive interferon-γ release assay or tuberculin skin test

A

DTH

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28
Q

The tuberculin skin test (TST) is also known as the

A

Mantoux test

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29
Q

The antigenic reagent of the Mantoux test is tuberculin (Mtb extract) or a

A

Purified Protein Derivative (PPD) of Mtb

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30
Q

In the PPD test, at 48-72 hours, we measure the ring of

A

Induration (not redness)

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31
Q

A PPD test > 15mm: considered positive for

A

Any persons

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32
Q

A PPD test > 5 mm: considered positive for

A

High risk populations

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33
Q

Like TSTs, these measure a person’s immune reactivity to Mtb

A

Interferon-γ release assays (IGRAs)

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34
Q

Blood T-lymphocytes from most persons that have been infected with Mtb will release

A

Interferon-γ (IFN-γ)

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35
Q

Whole blood alone: provides baseline level of

A

IFN-γ

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36
Q

Whole blood plus Mtb peptides: measures stimulated IFN-γ release in response to

A

Recombinant specific Mtb antigens

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37
Q

Whole blood plus a non-specific activator of WBCs (mitogen): demonstrates that WBCs are present and capable of secreting

A

IFN-γ

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38
Q

Performing a second diagnostic test when the initial test is negative is a strategy to increase

A

Sensitivity

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39
Q

Performing a second diagnostic test when the initial test is negative is a strategy to increase sensitivity, but this may reduce

A

Specificity

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40
Q

Performing a confirmatory test following an initial positive result is based upon both the evidence that

A

False positives are common

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41
Q

If the immune system CANNOT keep tubercle bacilli under control, or later becomes compromised (HIV, iatrogenic, age), focal granulomata break down and organisms

A

Escape, replicate, and can disseminate

42
Q

Active disease may represent reactivation, reinfection or progressive

A

Primary infection

43
Q

What are the intermediate risk factors for disease progression to TB?

A

Diabetes, Chronic renal failure, and Intravenous drug use

44
Q

What are some of the high risk factors for disease progression to TB?

A

HIV infection, immunosuppressive therapy, Silicosis, and abnormal CXR

45
Q

A person has no symptoms if they have a

A

Latent TB Infection (LTBI)

46
Q

Occurs when a TB infected lymph node erodes a vessel wall and tubercle bacilli are spread through the blood stream to other parts of the body and the rest of the lung

A

Miliary TB

47
Q

Diffuse miliary pattern is associated with appearance of

A

Millet Seeds

48
Q

Tissue injury is a consequence of immune response instead of specific

A

Toxins virulence factors

49
Q

Sputum*, aspirate, bronchoalveolar lavage (BAL), gastric lavage (GL) are respiratory specimens for

A

TB testing

50
Q

TB can also be tested for in the

-Does not require 24 hour test

A

Urine

51
Q

High volume of urine and tissue and body fluids to test for

A

TB

52
Q

In an immunocompromised patient, we can test for TB by testing the

A

Blood

53
Q

Specimens collected from normally sterile sites can be directly stained and inoculated to media, typically following a

A

Concentration step

54
Q

Specimens from non-sterile sites must first be decontaminated before further

A

Analysis

55
Q

Responsible for Liquefaction of non-sterile specimens

A

N-acetyl-L-cysteine (NALC)

56
Q

Kills contaminating bacteria

A

NaOH

57
Q

What are the two ways for direct pathogen visualization of TB?

A

Acid-fast stain and Fluorochrome stain

58
Q

The detection limit of the acid-fast stain is 10^4 AFB. What is the sensitivity of this test?

A

20-80%

59
Q

More sensitive than Acid-fast stain

-All positives must be confirmed using acid-fast stain or by another observer

A

Fluorochrome stain

60
Q

Some AFB do not stain well with

A

Fluorochromes

61
Q

Contamination should be an important consideration with

A

Direct pathogen visualization

62
Q

A characteristic of Mtb in the acid-fast stain is

A

Cording

63
Q

A virulence factor (toxic to phagocytes and other cells)

A

Cord factor (trehalose dimycolate)

64
Q

It fluorescences only in lipid environment (e.g., after metabolic incorporation into the outer membrane of mycobacteria) and not in aqueous solutions

-Artificial precursor of mycolic acids

A

Solvatochromic Trehalose

65
Q

Very fast and does not require any washes

A

Solvatochromic Trehalose

66
Q

Staining with Solvatochromic Trehalose requires

A

Bacterial metabolic activity

67
Q

What kind of staining will we see with

  1. ) Life Mtb
  2. ) Dead Mtb
  3. ) Effective antibiotic-treated Mtb
A
  1. ) Strong staining
  2. ) No signal
  3. ) Weak staining
68
Q

2017 ATS/IDSA/CDC guidelines recommend that both solid media and liquid media be inoculated for all specimens and incubated for

A

8 weeks

69
Q

Liquid media reduces

A

Average turn around time (TAT)

70
Q

Nucleid acid probes can be used for

A

Identification of TB

71
Q

All US clinicians and public health TB programs should have access to molecular tests to aid in the diagnosis of TB. Standard practice should include

A

NAA testing

72
Q

Should be performed on at least one respiratory specimen from each patient with signs and symptoms of pulmonary TB

A

NAAT testing

73
Q

For NAATs, is similar to that for smear examination but weeks faster than culture

A

Turn-Around-Time (TAT)

74
Q

NAATs are superior to smear examinations because they have greater

A

Specificity (`95% PPV) and Sensitivity

75
Q

~50-80% of smear negative, culture positive specimens are

A

NAAT positive

76
Q

It is recommend that acid-fast bacilli (AFB) smear microscopy be performed in all patients suspected of having

A

Pulmonary TB

77
Q

Should both be performed for every specimen obtained from an individual with suspected TB disease

A

Liquid and solid myobacterial cultures

78
Q

CDC suggests performing a diagnostic nucleic acid amplification test (NAAT) on the initial respiratory specimen from patients suspected of having

A

Pulmonary TB

79
Q

In AFB smear-negative patients with an intermediate to high level of suspicion for disease, what can we use as presumptive evidence of TB disease?

A

Positive NAAT

80
Q

Appropriate NAAT include the

A

MTD test and MTB/Rif test

81
Q

Ubiquitous environmental organisms that may colonize or infect humans

A

Non-tuberculous Myobacteria (NTMs)

82
Q

Pathogenesis may include trauma, inhalation of infectious aerosols or ingestion

A

NTMs

83
Q

What are the four clinically important NTMs and Runyon classification?

A

Group 1: Photochromogens
Group 2: Scotochromogens
Group 3: Nonphotochromogens
Group 4: Rapid growers

84
Q

M. kansasii and M. marinum (low temp) are two examples of

A

Photochromogens

85
Q

M. gordonae, M. xenopi, and M. scrofulaceum are two examples of

A

Scotochromogens

86
Q

M. avium complex (MAC) and M. ulcerans (low temp) are two examples of

A

Nonphotochromogens

87
Q

M. abscessus, M. chelonae, and M. fortuitum are the three

A

Rapid growers

88
Q

Causes chronic pulmonary infection involving upper lobes of the lungs, resembles Mtb clinically

A

M. Kansasii

89
Q

A major reservoir for M. Kansasii is

A

Tap water

90
Q

Dissemination is rare except in AIDS

-Responds quickly to antimicrobial therapy

A

M. Kansasii

91
Q

Sometimes cording is observed with M. kansasii but it is ID’d by

A

DNA probe

92
Q

M. Kansasii is classified as a

A

Photochromogen

93
Q

Cutaneous infection associated with exposure to salt/freshwater following trauma

A

M. marinum

94
Q

M. marinum causes which two granulomas?

A

Swimming pool granuloma and fish tank granuloma

95
Q

Most common in southern coastal states

  • Grows slowly at 30 ⁰C (no growth at 37 ⁰C)
  • Photochromogenic
A

M. marinum

96
Q

How do we ID M. marinum?

A

Biochemical/molecular ID

97
Q

Most commonly recovered nonpathogenic NTM (no treatment needed)

A

M. gordonae

98
Q

Found in soil and water, and it colonizes the respiratrory tract

-Long, wide, branching, beaded AFB

A

M. gordonae

99
Q

M. gordonae is classified as a

-i.e. it has pigmentation in the dark or in the light

A

Scotochromogen

100
Q

We use a DNA probe for ID of

A

M. gordonae

Microbiology Lecture Slides (24 decks)

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