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Microbiology > Bacteria of Skin & Nasopharynx > Flashcards

Bacteria of Skin & Nasopharynx Flashcards

1
Q

Where do streptococci reside?

A

nasopharynx, skin, GI, GU

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2
Q

What are the two genus of pyogenic gram + bacteria?

A

What are the two genus of pyogenic gram + bacteria?

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3
Q

What is the main morphological difference between staphylococci and streptococci?

A

Staphylocci: clusters
Streptococci: pairs/chains

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4
Q

What is a catalase test used for?

A

differentiating between staphylococci and streptococci species

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5
Q

What does catalase do?

A

Converts Hydrogen peroxide into water and oxygen

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6
Q

Which bacteria lack catalase?

A

Streptococci

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7
Q

Which bacteria produce catalase?

A

Staphylococci

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8
Q

Will a cell culture with H2O2 and streptococci produce Water and oxygen gas?

A

No

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9
Q

Will a cell culture with H2O2 and staphylococci produce Water and oxygen gas?

A

Yes

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10
Q

What makes staphylococci a major problem in hospitals? (2)

A

Resistant to drying/heat and resistant to many antibiotics

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11
Q

How is staphylococci species usually spread in hospital settings?

A

nasal and skin carriage

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12
Q

What are the two species of staphylococci?

A

staphylococcus aureus

staphylococcus epidermidis

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13
Q

Which staphylococcus species is less pathogenic?

A

s. epidermidis, part of normal microbiota

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14
Q

endocarditis from sharing needles or surgery would be most associated with which staphylococcus species?

A

staphylococcus epidermidis

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15
Q

what diagnostic test is used to differentiate between staphylococcus aureus and staphylococcus epidermidis?

A

coagulase test

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16
Q

Which species of staphylococcus produces coagulase?

A

staphylococcus aureus

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17
Q

prothrombin in combination with coagulase will cause fibrinogen to do what?

A

convert to fibrin (blood will clot)

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18
Q

What virulence factors make up the pathogenic capacity of staphylococcus aureus? (3)

A

Surface molecules
Extracellular factors
Toxins

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19
Q

List two surface molecules of S. aureus

A

Fibronectin binding protein

Protein A

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20
Q

Fibronectin binding protein is what kind of virulence factor?

A

adhesin

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21
Q

Which virulence factor of Staph aureus

  • binds to Fc of IgG1, IgG2, IgG4
  • linked to peptidoglycan
  • prevents phagocytosis (opsonization)
A

protein A

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22
Q

the surface molecule of S. aureus, fibronectin acts as what?

A

adhesin

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23
Q

Give an example of the extracellular factors produced by Staph aureus

A

Hemolysins “alpha toxin”

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24
Q

What does the alpha toxin produced by staph aureus do?

A

pokes holes in the membrane, forming transmembrane channels

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25
Q

Where do staphylococci reside?

A

nasopharynx, skin, GI

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26
Q

Why are the transmembrane channels formed by Staph aureus alpha toxin damaging to the cell?

A

lyses the mammalian cells

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27
Q

How is Staph aureus alpha toxin used diagnostically?

A

observe whether mixture of red blood cells lyses on contact with bacterial culture (if yes, bacteria contain alpha toxin)

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28
Q

What is the alpha toxin produced by Staph aureus primary virulence function?

A

lyse white blood cells

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29
Q

What are the three exotoxins associated with Staph aureus?

A
  • TSST-1
  • Exfoliative toxins A & B
  • Enterotoxins
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30
Q
  • TSST-1
  • Exfoliative toxins A & B
  • Enterotoxins
A

TSST-1 and enterotoxins

31
Q

Which of the Staph aureus exotoxins cause toxic shock syndrome?

A

TSST-1

32
Q

What does exfoliative toxins A & B do? (Staph aureus exotoxin)

A

Proteases that cleave desmosomal proteins of the skin

33
Q

Exfoliative toxins A & B produced by Staph aureus were thought to be superantigens but are actually?

A

proteases

34
Q

What is the protein that exfoliative toxins A & B of Staph aureus cleave?

A

desmosomal proteins of the skin

35
Q

Enterotoxins produced by Staph aureus causes what kind of symptoms?

A

food poisoning

36
Q

Why don’t the enterotoxins of Staph aureus cause toxic shock syndrome since they are superantigens like TSST-1?

A

location, enterotoxins occur in the gut producing food poisoning

37
Q

Where can Staph infections occur? (5)

A
  • endocarditis
  • genitourinary
  • muskuloskeletal
  • skin & soft tissue
  • Toxin based
38
Q

List several skin infections caused by Staphylococcus species

A
  • Carbuncle
  • Folicullitis
  • Furuncle
  • Impetigo
39
Q

Skin infection that Starts as a pus-filled epidermal blister that breaks to leave thick yellowish crust (common in children)

A

impetigo

40
Q

What are symptoms of a Furuncle (boil)?

A

hot, tender, low fever

41
Q

What is folicullitis?

A

infection in or around hair follicle and usually confined to that area

42
Q

Why can furuncles be hard to treat?

A

the coagulase produced by bacteria can cause clotting wall around bacteria

43
Q

What is a carbuncle?

A

confluence of boils which have traversed deep into the dermis entering subcutaneous fat

44
Q

Suppurative infections can occur on the skin and where else?

A

surgical/burn wound infections and pneumonia

45
Q

Scalded skin syndrome is common in?

A

children (esp <5)

46
Q

What are symptoms of scalded skin syndrome?

A

Rash and peeling skin, fever

47
Q

Are the rash and peeling skin of scalded skin syndrome infected with bacteria?

A

no, peeling caused by exfoliative toxins

48
Q

scalded skin syndrome is caused by?

A

exfoliative toxins A & B from Staph aureus bacteria

49
Q

What are symptoms associated with Toxic shock syndrome caused by TSST-1?(6)

A

Fever, rash, respiratory distress, irrational behavior, vomiting, multi-organ failure

50
Q

What is treatment consist of for toxic shock syndrome (tsst-1)?

A

supportative measures & antibiotics

51
Q

Staph food poisoning is different from other staph related infections because?

A

No infection, only intoxication by staph enterotoxins

52
Q

What is the common cause of staph food poisoning?

A

staphylococcal enterotoxin

53
Q

What is one of the ways to differentiate between intoxication and bacterial infection (of GI)?

A

time period of when symptoms first appear, bacterial toxins act much quicker (span of hours) while bacterial infection can take up to 48 hours

54
Q

Why will heating food not make staph aureus infected food safe to eat?

A

the enterotoxins are heat stable

55
Q

What is treatment for Staph food poisoning? (2)

A
  • hydration

- monitor/correct electrolytes

56
Q

What are symptoms of food poisoning? (2)

A

severe vomiting and diarrhea

57
Q

Why is there only clinical presentation in diagnosing staph food poisoning?

A

There is no infection, (no diagnostic test to do), only toxins are causing distress to body

58
Q

diagnosis of localized & systemic infections of Staph include: (3)

A
  • culture from abscess, lesion, sputum, or blood sample
  • catalase, coagulase tests
  • antibiotic sensitivity (bc MRSA!)
59
Q

What is normal treatment for Staph skin infection? (2)

A
  • Drainage, topical treatment

- Chronic - systemic antibiotic

60
Q

What is typical treatment for focal & systemic staph infection?

A

a

61
Q

80-90% of Staph aureus strains are have what?

A

Beta lactamase

62
Q

Most strains of Staph aureus even though they may have betalactamase are resistant to […] spectrum of B-lactams

A

Most strains of Staph aureus even though they may have betalactamase are resistant to limited spectrum of B-lactams

63
Q

What is methicillin?

A

betalactam antibiotic that was used some time back

64
Q

What protein confers resistance to methicillin?

A

mecA - encodes mutant penicillin binding protein (PBP2a)

65
Q

HA-MRSA has a high chance of having what kind of resistance to antibiotics?

A

broad spectrum of antibiotics (MDR) as well as most all first line antibiotics

66
Q

CA-MRSA is rarely accompanied by resistance to what?

A

other antibiotics

67
Q

Hospital Acquired MRSA is typically found where? In whom?

A

hospitalized, older individuals with immunological deficiencies

68
Q

HA-MRSA is MDR, list some antibiotics that it is resistant to? (5)

A

tetracycline, macrolides, fluoroquinolones, aminoglycosides, Tm/sulfa)

69
Q

Transposable genetic elements that have gotten so big that they no longer able to transpose (large, non-mobile cassette that captures transposons & plasmids)

A

pathogenicity islands

70
Q

HA-MRSA is found in hosptialized individuals while CA-MRSA is usually found in whom?

A

otherwise healthy individuals who have not been in the hospital for at least one year

71
Q

CA-MRSA is usually found as what kind of infections? (area of body)

A

skin

72
Q

What size “pathogenicity island” is found to be in CA-MRSA genomes?

A

small

73
Q

the mecA small “pathogenicity island” has lost and gained what functions?

A

loss of MDR but now it’s mobile

Microbiology (7 decks)

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