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MICROM 442 > Exam 2 Lecture 12 > Flashcards

Exam 2 Lecture 12 Flashcards

Corynebacteria, Listeria, Bacillus

1
Q

Describe the Gram Stain of Corynebacterium matruchotii

A

Gram Positive rods with clubbed ends

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2
Q

True or False: Humans are the only natural reservoir of Corynebacterium diphtheriae

A

True

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3
Q

How is corynebacterium diphtheriae spread? (3)

A
  1. Respiratory droplets
  2. Skin lesions
  3. Fomites
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4
Q

Where do convalescent patients commonly carry corynebacterium diphtheriae?

A

Pharynx, nasal area

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5
Q

Name the principal virulence factor for corynebacterium diphtheriae

A

Diphtheria toxin (DT)

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6
Q

The __ subunit is catalytic, while the __ subunit accomplishes cell binding

A

A, B

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7
Q

Via acidification of the endosome, the B subunit releases the A subunit from the endosome into the cytoplasm, where it catalyzes ____-_________ of _________ _____ __.

A

ADP-ribosylation

elongation factor 2

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8
Q

True or False: many molecules diphtheria toxin are needed to kill cells.

A

False - just 1 molecule is sufficient

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9
Q

What encodes the diphtheria toxin?

A

lysogenic bacteriophage

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10
Q

True or False: C. diphtheriae strains that lack the lysogenic bacteriophage do not produce diphtheria toxin and do not cause the disease diphtheria.

A

True

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11
Q

Name the chromosomal gene (not phage encoded) that represses the expression of DT at high iron conditions

A

DtxR

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12
Q

Where is most host iron?

A

Heme bound or intracellular

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13
Q

True or False: When iron is low, DtxR represses expression of DT

A

False

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14
Q

What is DT co-regulated with? (2)

A
  1. Endogenous genes encoding bacterial iron transport system

2. HmuO (heme oxygenase)

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15
Q

What is the function of heme oxygenase?

A

It utilizes heme and hemoglobin as a source of iron

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16
Q

Diphtheria is historically a ______ disease.

A

childhood

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17
Q

Name the key local effects of diphtheria toxin (4)

A
  1. Pharyngitis
  2. Epithelial cell necrosis & inflammation
  3. Formation of a pseudomembrane
  4. Mechanical obstruction of airway
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18
Q

What is characteristic about the pseudomembrane?

A

It is a gray/yellow/white membrane with surrounding inflammation

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19
Q

Name the key systemic effects of DT (2)

A
  1. Paralysis of soft palate and muscle groups like the diaphragm
  2. Myocarditis and cardiomyopathy
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20
Q

What heart problems may arise from DT? (3)

A

heart enlargement, arrhythmia, pump dysfunction (which can lead to shortness of breath)

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21
Q

What infections caused by DT usually arise without systemic complications?

A

Superficial skin infections

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22
Q

What compound is used to inhibit oropharyngeal microbiota and Gram (-) bacteria?

A

Potassium tellurite

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23
Q

What color colony does diphtheria produce?

A

Dark brown/black

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24
Q

What leads to the dark brown halo?

A

H2S production from L-cysteine

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25
Q

How has diphtheria been prevented/almost eliminated?

A

DTaP vaccine

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26
Q

DTaP consists of toxin treated with ______ to mitigate potential toxicity and retain the immunogenicity of the native form of the antigen.

A

formalin

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27
Q

What does the diphtheria toxoid inactive?

A

The B subunit of DT (but maintains subunit A’s structure/antigenicity)

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28
Q

The __ subunit of DT ensures that the toxin is taken up by endocytosis, while acidification of ____ releases the __ subunit into the cytosol

A

B; endosome; A

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29
Q

Because the toxoid inactivates the B subunit, the __ subunit cannot translocate from the
______ to the ______

A

A
endosome
cytoplasm

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30
Q

________ may be used for life threatening illness in people who are not vaccinated.

A

anti-toxin

31
Q

True or False: Corynebacterium jeikeium also produces DT

A

False

32
Q

Where is corynebacterium jeikeium typically found?

A

skin

33
Q

What systemic diseases can corynebacterium jeikeium cause? (5)

A
  1. bacteremia
  2. endocarditis
  3. pneumonia
  4. osteomyelitis
  5. meningitis
34
Q

Where is corynebacterium jeikeium typically acquired?

A

Hospital (nosocomial infection)

35
Q

True or False: corynebacterium jeikeium is not antibiotic resistant thus it responds well to a variety of antibiotics

A

False - it is multi-drug resistant

36
Q

Describe the Gram Stain of Listeria

A

Short Gram Positive coccobacilli

37
Q

Listeria monocytogenes is an ________ pathogen

A

intracellular!!

38
Q

Does listeria contain catalase?

A

Yes

39
Q

What type of hemolysis does listeria display on blood agar?

A

Beta hemolysis (small colonies w/ discrete zones)

40
Q

What environmental conditions allow for growth of listeria? (3)

A
  1. Low temps
  2. Low pH
  3. High salt
41
Q

What part of the body does listeria colonize?

A

Large intestine

42
Q

_____ and ____ allow for listeria to bind and invade non-phagocytic cells

A

lnlA, lnlB (internalins)

43
Q

What does lnlA bind to?

A

e-cadherin on intestinal epithelial cells

44
Q

What does lnlB bind to?

A

hepatocyte growth factor receptor

45
Q

______ are involved in crossing critical anatomical membranes

A

internalins

46
Q

what is the name of the cholesterol-dependent pore-forming cytolysin in listeria?

A

listeriolysin (LLO)

47
Q

True or False: Listeria grows well in the cytoplasm but is unable to replicate in the phagosome

A

True

48
Q

what does LLO do?

A

causes lysis of the bacteria-containing phagosome

49
Q

in addition to listeriolysin, _______ help release bacteria from the phagosomes

A

phospholipases

50
Q

Lytic activity is limited by __ _____, _________ _________ and ________ _______

A

pH optima
translational regulation
proteolytic degradation by proteasome (PEST)

51
Q

What is the surface protein that leads to polar distribution in Listeria?

A

ActA

52
Q

What does ActA do?

A

Promotes actin polymerization and the “comet tails” that push bacteria through the cytoplasm

53
Q

Immunity depends upon _____ __ cells

A

CD8+ T cells

54
Q

Listeria is frequently ______

A

foodborne

55
Q

Who is particularly vulnerable to listeria infection? (6)

A
  1. Pregnant women and their fetuses
  2. Elderly
  3. Alcoholics
  4. Diabetics
  5. Compromised individuals
  6. Corticosteroid users
56
Q

Vertical transmission of listeria can occurs via _________ ________

A

feto-placental infections

57
Q

In people vulnerable to listeria, they may get _______ or _______

A

meningitis

septicemia

58
Q

What listeria symptoms do immune competent hosts suffer from?

A
  • GI infections [high inoculum]

- mild flu like symptoms [low inoculum]

59
Q

What is the mortality rate of Listeria when critical anatomical barriers are crossed?

A

20-30%

60
Q

Listeria is primarily diagnosed by ______

A

culture

61
Q

For diagnosis of Listeria, cultures can be taken from ….. (5)

A
  1. CSF
  2. blood
  3. amniotic fluid
  4. placenta
  5. fetal tissue
62
Q

Describe the Gram Stain of Bacillus Cereus

A

Long/wide Gram Positive rods

63
Q

What is unique about bacillus cereus?

A

able to form spores

64
Q

Bacillus cereus is __ hemolytic

A

beta

65
Q

Bacillus cereus can decolorize to appear ___

A

GNR

66
Q

Name characteristics of spores formed by bacillus cereus (4)

A
  1. heat and desiccation resistant
  2. metabolically inactive
  3. autoclave withstanding
  4. germinate into cells after decades of persistence
67
Q

What does bacillus cereus produce?

A
  • enterotoxins
68
Q

Enterotoxins can be broken down into 2 categories. What are they?

A
  1. heat stable toxins

2. heat labile toxins

69
Q

The heat-stable toxin is _____ tolerant and leads to ________

A

acid, vomiting

70
Q

which form of the toxin is a circular peptide with ionophore activity?

A

heat stable

71
Q

The heat-labile toxin is associated with ______ illness

A

diarrheal

72
Q

GI infections are found in ___ of food tested. ____ is a common vehicle for illness.

A

25%

rice

73
Q

The heat-stable form is due to ……

A

toxin contamination of food (2-3 hr incubation)

74
Q

The heat-labile form is due to ………………

A

intestinal bacterial replication (6-24 hr incubation)

MICROM 442 (26 decks)

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