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NBME Micro > Bacteria: Gram Positive Bacilli > Flashcards

Bacteria: Gram Positive Bacilli Flashcards

1
Q

List the Gram Positive Bacilli

A
  1. Bacillus Anthracis
  2. Bacillus Cereus
  3. Clostridium Tetani
  4. Clostridium Botulinim
  5. Clostridium Difficile
  6. Clostridium Perfingens
  7. Corynebacterium Diphtheriae
  8. Listeria Monocytogenes
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2
Q

Bacillus anthracis is a

A
  1. gram-positive
  2. spore-forming
  3. bacillus
  4. chains
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3
Q

Cutaneous anthrax

A

(the most common manifestation of Bacillus anthracis infection) presents with an area of central necrosis with surrounding erythema, edema, and eschar formation

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4
Q

Bacillus anthracis and cereus bacteria are

A

gram-positive bacilli that occur in chains

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5
Q

The capsule of Bacillus anthracis is composed of

A

poly-γ-D-glutamic acid (a polypeptide)

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6
Q

Bacillus anthracis needs

A

oxygen to sporulate (but can make ATP with and without oxygen; ie, aerobic or facultatively anaerobic)

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7
Q

Bacillus anthracis and cereus bacteria have

A

the ability to form metabolically inactive spores, which are resistant to decontaminants such as heat, chemicals, and radiation

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8
Q

The edema factor exotoxin of Bacillus anthracis

A

mimics adenylate cyclase → increase in cAMP → edema and dysfunction of phagocytes

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9
Q

The lethal factor exotoxin of Bacillus anthracis is

A
  1. a protease that cleaves mitogen-activated protein kinase (MAPK) → apoptosis, tissue necrosis multisystem physiologic disruption, and death
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10
Q

The lethal factor exotoxin of Bacillus anthracis is responsible for

A

the tissue necrosis seen in cutaneous anthrax

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11
Q

Wool sorters

A

are historically associated with pulmonary anthrax/inhalation anthrax (woolsorters’ disease) due to inhalation of Bacillus anthracis spores carried in animal wool (though this form of anthrax is rare in developed countries)

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12
Q

Pulmonary anthrax/inhalation anthrax primarily manifests as

A

hemorrhagic mediastinitis with bloody pleural effusions

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13
Q

Chest X-ray of patients with hemorrhagic mediastinitis from pulmonary anthrax/inhalation anthrax may show a

A

widened mediastinum or pleural effusions

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14
Q

_______ are effective against Bacillus anthracis

A
  1. fluoroquinolones

2. doxycycline

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15
Q

Bacillus cereus

A

ingestion of Bacillus cereus preformed toxin (classically associated with reheated rice) can cause early onset food poisoning → nausea/vomiting (early onset, within 6 hours) or watery diarrhea, abdominal cramps (onset within 6 to 15 hours)

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16
Q

Bacillus cereus is a

A
  1. gram-positive
  2. spore-forming
  3. bacillus
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17
Q

Bacillus cereus infection is classically associated with

A

reheated rice (warm temperatures → spore germination → enterotoxin production (preformed toxin)→ early onset food poisoning)

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18
Q

Clostridium tetani is

A
  1. gram-positive
  2. spore-forming
  3. bacillus
  4. obligate anaerobes
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19
Q

Clostridium tetani bacteria have the ability to

A

form metabolically inactive spores, which are resistant to environmental decontaminants such as heat, chemicals, and radiation

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20
Q

Clostridium tetani infection is classically associated with

A
  1. puncture wounds from barbed wire

2. puncture wounds from rusty nails

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21
Q

The metabolically inactive spores of Clostridium tetani are

A

ubiquitous in soil

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22
Q

The classic findings in tetanus include

A

trismus (a spastic paralysis of the jaw muscles (lockjaw)), and risus sardonicus (continuous contraction of the facial muscles resulting in an “evil smile” appearance)

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23
Q

The spasmodic contraction seen in tetanus can

A

extend to the neck and back → opisthotonos (backward arching of the head, neck, and spine)

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24
Q

The tetanus toxin of Clostridium tetani

A
  1. travels via retrograde axonal transport to the spinal cord
  2. protease that cleaves SNARE proteins
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25
Q

Tetanus toxin is called

A

tetanospasmin

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26
Q

The tetanus toxin (tetanospasmin) of Clostridium tetani functions to

A

the tetanus toxin (tetanospasmin) of Clostridium tetani cleaves SNARE proteins → inhibition of GABA and glycine release (inhibitory neurotransmitters) from Renshaw cells in the spinal cord→ muscle spasms, spastic paralysis, and hyperreflexia

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27
Q

The tetanus toxin (tetanospasmin) of Clostridium tetani acts on

A

the tetanus toxin (tetanospasmin) of Clostridium tetani acts on Renshaw cells (inhibitory interneurons in grey matter of the spinal cord) → inhibition of GABA and glycine release → muscle spasms, spastic paralysis, and hyperreflexia

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28
Q

Prevention of tetanus includes

A

administration of tetanus vaccine, which consists of deactivated tetanus toxin (often given with the diphtheria toxoid and acellular pertussis vaccine (DTaP))

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29
Q

Clostridium botulinum is

A
  1. gram-positive
  2. spore-forming
  3. bacillus
  4. obligate anaerobes
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30
Q

The anaerobic environment of improperly canned food allows

A

spore germination and growth of Clostridium botulinum

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31
Q

Clostridium botulinum bacteria have the

A

ability to form metabolically inactive spores, which are resistant to environmental decontaminants such as heat, chemicals, and radiation

32
Q

Clostridium botulinum can cause

A

a descending flaccid paralysis (due to production of botulinum toxin) starting from the cranial nerves

33
Q

Clostridium botulinum can cause a descending flaccid paralysis due to

A

production of botulinum toxin

34
Q

Clostridium botulinum can cause a descending flaccid that may first affect

A

the eyes, causing ptosis and diplopia

35
Q

Botulinum toxin of Clostridium Botulinum is a

A

botulinum toxin of Clostridium botulinum is a protease that cleaves SNARE → inhibition of presynaptic release of acetylcholine (an excitatory neurotransmitter) at the neuromuscular junction → flaccid paralysis

36
Q

Infant botulism results from

A

ingestion of spores, which are able to colonize the GI tract of infants due to a not yet fully developed GI flora (in contrast to adults, who contract botulism from eating preformed toxin)

37
Q

Honey

A

honey is frequently contaminated with Clostridium botulinum spores and it is advised that infants are not allowed to consume honey until they are at least 12 months of age

38
Q

Clostridium difficile is

A
  1. gram-positive
  2. spore-forming
  3. bacillus
  4. obligate anaerobes
39
Q

Clostridium difficile bacteria have the ability to

A

form metabolically inactive spores, which are resistant to environmental stressors such as heat, chemicals, and radiation

40
Q

_______ is the most significant risk factor for Clostridium difficile infection

A

prior exposure to antibiotics (particularly clindamycin) is the most significant risk factor for Clostridium difficile infection

41
Q

Prevention of Clostridium Difficile

A

contact precaution and infection control measures (hand hygiene with soap and water, use of gloves) help prevent spread of Clostridium difficile (and is especially important for protection of patients who are taking antibiotics, such and clindamycin)

42
Q

toxin A (enterotoxin) of Clostridium difficile

A

toxin A (enterotoxin) of Clostridium difficile binds the brush border membranes of the gut → damage to the mucosal lining of the colon → diarrhea

43
Q

Clostridium difficile can cause

A

watery diarrhea (often with abdominal pain, fever, and leukocytosis)

44
Q

Toxin B (cytotoxin) of Clostridium difficile

A
  1. toxin B (cytotoxin) of Clostridium difficile disrupts the cytoskeleton via actin depolymerization → necrosis of colonic mucosal surfaces → pseudomembrane formation
  2. toxin B (cytotoxin) of Clostridium difficile causes pseudomembrane formation (toxin B disrupts the cytoskeleton via actin depolymerization → necrosis of colonic mucosal surfaces → pseudomembrane formation)
45
Q

Diagnosis of Clostridium difficile infection can be made by

A

detection of its toxins (A and B) in the stool

46
Q

_____ is effective against Clostridium difficile

A
  1. oral vancomyocin

2. metronidazole

47
Q

Clostridium perfringens is

A
  1. gram-positive
  2. spore-forming
  3. bacillus
  4. obligate anaerobe
48
Q

Clostridium perfringens infection is associated with

A

military combat wounds

49
Q

Clostridium perfringens bacteria have the ability to

A

form metabolically inactive spores, which are resistant to decontaminants such as heat, chemicals, and radiation

50
Q

the metabolically inactive spores of Clostridium perfringens are

A

ubiquitous in soil

51
Q

Clostridium perfringens can cause

A

necrotizing skin and soft tissue infection, which can progress to myonecrosis and gas gangrene

52
Q

The alpha toxin of Clostridium perfringens

A
  1. the alpha toxin of Clostridium perfringens is a lecithinase that cleaves lecithin (a phospholipid) molecules of phospholipid complexes → damage to cell membranes → myonecrosis and hemolysis
  2. the alpha toxin of Clostridium perfringens is a lecithinase that cleaves lecithin (a phospholipid) molecules of phospholipid complexes → damage to cell membranes → hemolysis
53
Q

Clostridium perfringens produces a

A

double zone of beta-hemolysis when plated on blood agar (both the alpha and theta toxin of Clostridium perfringens have hemolytic activity)

54
Q

The first-line treatment for Clostridium perfringens tissue infection is

A

surgical debridement and administration of antimicrobials, particularly penicillin

55
Q

Ingestion of a large quantity of Clostridium perfringens spores can cause

A

late-onset food poisoning, characterized by watery diarrhea

56
Q

Corynebacterium diphtheriae bacteria

A
  1. gram positive
  2. bacillus
  3. form V or Y shaped chains
57
Q

The cytoplasm of Corynebacterium diphtheriae contains

A

metachromatic granules that stain with aniline dyes (the metachromatic granules stain red while the remainder of the bacillus stains blue)

58
Q

Diptheria Toxin of Corynebacterium diptheriae

A
  1. diphtheria toxin of Corynebacterium diphtheriae inhibits elongation factor-2 by ADP ribosylation (a mechanism similar to that of exotoxin A of Pseudomonas aeruginosa)
  2. the diphtheria toxin of Corynebacterium diphtheriae causes cell necrosis → dense, grey tonsillar/pharyngeal pseudomembrane formation
59
Q

Laryngeal diphtheria can

A

lead to severe lymphadenopathy → characteristic swelling of the neck known as “bull neck”

60
Q

Corynebacterium diphtheriae is transmitted via

A

respiratory droplets

61
Q

Presence of the diphtheria toxin of Corynebacterium diphtheriae in the bloodstream can result in

A

cardiac toxicity → myocarditis, arrhythmia, and heart failure

62
Q

The diphtheria toxin of Corynebacterium diphtheriae can cause

A

nerve damage (demyelination) → paralysis that typically begins in the posterior pharyngeal wall and soft palate

63
Q

Corynebacterium diphtheriae will grow as

A

dark black colonies on cystine-tellurite agar

64
Q

Corynebacterium diphtheriae can be cultured in

A

Loeffler’s medium (where it develops metachromatic granules seen in the cytoplasm after staining with an aniline dye)

65
Q

The ELEK test is used to differentiate

A

toxigenic from nontoxigenic Corynebacterium diphtheriae

66
Q

The Corynebacterium diphtheriae toxoid vaccine is

A

typically only administered in developed countries and consists of inactivated diphtheria exotoxin (often given with the tetanus toxoid and acellular pertussis vaccine (DTaP))

67
Q

Listeria Monocytogenes

A
  1. gram positive
  2. Bacillus
  3. facultative intracellular pathogens
  4. catalase positive
68
Q

Listeria monocytogenes colonies are

A

weakly beta-hemolytic (surrounded by a small zone of complete hemolysis when plated on blood agar)

69
Q

Listeria monocytogenes bacteria exhibit

A

tumbling motility in broth

70
Q

Listeria monocytogenes bacteria form

A

“rocket tails” via actin polymerization that allow movement within and between host cells

71
Q

Listeria monocytogenes bacteria are able to

A

grow in temperatures as low as 0°C and exhibit motility at temperatures between 22-27°C

72
Q

Listeriosis outbreaks are associated with

A

dairy products like milk, soft cheese, and ice cream

73
Q

the incidence of listeriosis is significantly higher in

A

pregnant women

74
Q

Listeria monocytogenes is the third most common cause of

A

neonatal meningitis (following Streptococcus agalactiae (group B strep) and E. coli)

75
Q

Listeria monocytogenes is a common cause of

A

meningitis in adults over 60 and immunocompromised patients

76
Q

___ is effective against Listeria monocytogenes

A

ampicillin

NBME Micro (36 decks)

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