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MBE3 > Mycobacterium > Flashcards

Mycobacterium Flashcards

1
Q

Mycolic acids in cell wall
Gram+ weak staining: use acid-fast stain
or specific fluorescent detection

A

Mycobacteria

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2
Q 
Facultative intracellular growth (in macrophages)
Obligate aerobe (growth in lung macrophages)
A

Mycobacteria

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3
Q

Humans are reservoir
• airborne transmission (as few as 10 cells
can result in infection)

A

Mycobacteria

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4
Q

Don’t need alot of cells to infect

A

Mycobacteria

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5
Q

treat with alkaline-alcohol to extract lipid mycolic acids

A

Acid-fast stain
McKane ‘96 Table 3-3, Fig.3-13 Walker ’98 Fig.9-2
(

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6
Q

Acid fast cells stain what color.

Non acid fast?

A

Red

Blue

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7
Q

Mycobacterial cell wall structure

A

cord factor (glyco-lipid)

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8
Q

Structural mycobacterial cell wall components which are Virulence Factors

A

Mannose Caped lipoarabinomanna
Cord factor (glyco-lipid)
Arabinogalactin

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9
Q

Slow, cord-like growth
strongly correlates
with virulence.

A

Mycobacterium
Cord-like growth results from adherence of cell surface
lipid mycolic acids and glyco-lipids

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10
Q

Virulence Factors (2) M.tuberculosis and M.leprae

A

Facultative intracellular growth in alveolar and other macrophages:
inhibition of phago-lysosome fusion

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11
Q

disease is caused by the immune response,

NOT by the mycobacteria.

A

While many “virulence factors” are listed, their virulence results from the challenge that
they provide to the immune response (typically DTH: CD4+ T-cells + macrophages)
because (in most cases) the disease is caused by the immune response,
NOT by the mycobacteria.

Virulence Factors (2) M.tuberculosis and M.leprae

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12
Q

………………………. is a “life-long” pathogen:

once infected, you may be asymptomatic but never cured

A

Mycobacterium tuberculosis is a “life-long” pathogen:
once infected, you may be asymptomatic but never cured

TB granuloma surrounded by punctate nuclei
of lung tissue and inflammatory leukocytes.
Central area of necrosis where nuclei have
been destroyed.

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13
Q

CMI to Mycobacterium tuberculosis

A

TB granuloma surrounded by punctate nuclei
of lung tissue and inflammatory leukocytes.
Central area of necrosis where nuclei have
been destroyed.

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14
Q

Effective CMI is capable of localizing and stopping infection by …………………….. Chronic …………… is
typical.

A

Effective CMI is capable of localizing and stopping infection by M.tuberculosis. Chronic TB is
typical.

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15
Q

young children under 5 years have a high risk for developing progressive ………………… due
to insufficient immune system development/activation.

A

young children under 5 years have a high risk for developing progressive TB due
to insufficient immune system development/activation.

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16
Q

Breathing impairment in TB is not due to tuberculosis bacilli but by the …………………………………….

A

Breathing impairment in TB is not due to tuberculosis bacilli but by the macrophage-induced tissue
destruction

17
Q

However, acute (‘open’) TB [also known as “secondary tuberculosis” or in older terms
“galloping consumption” caused by “……………..” of prior infection
- while rare (life-time risk is assessed as <12% for carriers, or less) it is VERY contagious!
Isolation of acute TB cases is mandatory.
Endogenous reactivation is stimulated by ………………..

A

However, acute (‘open’) TB [also known as “secondary tuberculosis” or in older terms
“galloping consumption” caused by “endogenous reactivation” of prior infection
- while rare (life-time risk is assessed as <12% for carriers, or less) it is VERY contagious!
Isolation of acute TB cases is mandatory.
Endogenous reactivation is stimulated by stress, malnutrition and HIV

18
Q

OUTCOMES of untreated primary TB [results for non-immune-compromised patents]:
• …..% no disease
• …..% clinical TB (2% pulmonary + 3% extrathoracic + 1% both)
• …….% progressive systemic disease and death.

A

OUTCOMES of untreated primary TB [results for non-immune-compromised patents]:
• 91% no disease
• 6% clinical TB (2% pulmonary + 3% extrathoracic + 1% both)
• 3% progressive systemic disease and death.

19
Q

Mantoux Reaction

A 
A positive tuberculin test to
subdermal PPD (processed
protein derivative of the cell
wall of the opportunistic
intracellular pathogen
Mycobacterial tuberculosis).
20
Q

Mantoux Reaction

Positive and Negative results

A

Positive test: >10 mm redness

Strongly positive: >20mm red

21
Q

M.bovis (

A

Exposure to living attenuated mycobacterium, known as Bacille Calmette-Guérin (BCG), a
derivative of M.bovis (which may be identical to M.tuberculosis based on whole genome sequencing):
• little virulence in humans (but infectious in immune-compromised persons)
• some protective immunity (when given to young children)
• BCG vaccination is discouraged in USA because it gives a positive tuberculin test, thus removing
an important diagnostic screening tool. (And M.bovis causes disease in immune-compromised persons.)

22
Q

Bacille Calmette-Guérin (BCG),

A

Vaccination
Exposure to living attenuated mycobacterium, known as Bacille Calmette-Guérin (BCG), a
derivative of M.bovis (which may be identical to M.tuberculosis based on whole genome sequencing):
• little virulence in humans (but infectious in immune-compromised persons)
• some protective immunity (when given to young children)
• BCG vaccination is discouraged in USA because it gives a positive tuberculin test, thus removing
an important diagnostic screening tool. (And M.bovis causes disease in immune-compromised persons.)

23
Q

TB and HIV

A

HIV infections, with its Acquired
Immune Deficiency Syndrome (AIDS),
has caused a recent increase in TB

24
Q

Mycobacterium leprae:

A

diverse CMI responses

25
Q

TH1-response
macrophages kill nerves;
macules and plaques without sensation

A

Mycobacterium leprae: diverse CMI responses

Tuberculoid

26
Q

Bad prognosis
for recovery
Highly
infectious

A

lepromatous

27
Q 
Loss of CMI
(or TH2-response
CTL lysis and
loss of tissue)
(including nerves
A

Leprosy

28
Q

Multidrug therapy: Dapsone + rifampin + clofazimine

Rising resistance is becoming a problem.

A

Tuberculoid treatment

29
Q

Tuberculoid vs Lepromatous Leprosy
Ability to survive
and live in lung
macrophages

A

M.tuberculosis

obligate aerobic

30
Q

Tuberculoid vs Lepromatous Leprosy
Epidemiology:
Close physical
contact

A

M.leprae

31
Q 
Tuberculoid vs Lepromatous Leprosy
Treament
multidrug therapy:
dapsone +
rifampicin + (for
lepramatous form)
clofazimine
2+ years
A

M.leprae

32
Q

Norcadia

Neg or Pos

A

Pos

33
Q

mycolic acid in cell wall: “partially acid-fast”

Test to distinguish Nocardia from fungal look-alikes

A

Nocardia

Gram+ (poor staining)

34
Q

Opportunistic pathogen

in immuno-compromised patients

A

Nocardia

MBE3 (13 decks)

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