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Medical Microbiology > L15: Infections of Skin and Soft Tissues! > Flashcards

L15: Infections of Skin and Soft Tissues! Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

Which of the following biochemical tests is used to differentiate between E. coli (-) and P. aeruginosa (+)?
A. Coagulase
B. Oxidase
C. Catalse

A

B. Oxidase

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2
Q

True or False: Coagulase is a biochemical test used to differentiate between staphylococcus aureus (+) and staphylococcus (-)

A

True
- Converts fibrinogen to fibrin

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3
Q

Which biochemical test is used to differentiate between staphylo (+) and strepto (-)?
A. Coagulase
B. Oxidase
C. Catalase

A

C. Catalase

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4
Q

True or False: Staphylococcus is catalase (+), pseudomonas aeruginosa is oxidase (+) and staphylococcus aureus is coagulase (+)

A

True

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5
Q

Which three bacteria make up NF?

A
  1. Cutibacterium acnes
  2. Diptheroids (aerobic, gram + bacilli)
  3. Staphylococcus epidermis
    - staphylococcus negative
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6
Q

In addition two HSV (most common viral agent), bacteria and fungi can cause direct infection of skin.

Give three examples of bacterial pathogens that can cause direct skin infection:

Give one example of a fungi that can cause direct skin infection:

A

Bacteria
- S. aureus
- Strep pyrogenes
- Cutbacterium acnes

Fungi
- T. rubrum

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7
Q

Describe cutibacterium acnes:
-Gram (+) or (-)?
-Shape
-O2 or no?

A

Cutibacterium Acnes
- Gram (+)
- Rod
- Anaerobic
- Diptheroids

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8
Q

____ is the predominant anaerobic member of the normal skin flora that colonizes hair follicles
A. S. aureus
B. Cutibacterium acnes
C. Streptococcus pyogenes

A

B. Cutibacterium acnes

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9
Q

How does Cutibacterium acnes degrade sebum into inflammatory substance, which attracts WBC’s
A. Produces protease
B. Produces lipase
C. Produces degradative enzyme

A

B. Produces lipase

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10
Q

___ is the most common skin disease (primarily in teens) and is initially caused by alteration in the physiology of subaceous glands and hair follicles

A

Acne Vulgaris

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11
Q

What are three of the ways that Acne Vulgaris can present?

A

1) Comedome -
(non-inflammatory lesion)
2) Inflammatory Lesion
3) Both

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12
Q

How does inflammatory acne happen?

A

Overgrowth of NF (like C. acnes)

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13
Q

What are two factors that cause the microcomedome to form?

A

1) Increased sebum produced
2) Follicular canal becomes plugged due to either
a - hyperproliferization of keratin
b - desquamation of cell lining the canal

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14
Q

True or False: Acne is a non-infectious process when C. acnes is absent

A

True

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15
Q

Microcomedomes may evove into non-inflammatory comedones, with the surface pore of follicular canal being either open or closed.

What is another name for an Open Comedone?

What is another name for a Closed Comedone?

A

Open Comedone - Black Heads

Closed Comedone - White Heads

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16
Q

The plug of comedome disrupts the normal movement of ___ and ___ cells, as well as sebum.

This leads to enlarged and pressurized follicle, which eventually ruptures

A

hair and skin cells

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17
Q

A ruptured hair follicle either heals or….

A
  1. Sebum leaks out
  2. Formation of papule/pustule (inflammatory acne)
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18
Q

Inflammatory lesions (infected/colonized by C. acnes) may progress into ___ => _____ => _____

A

papules => pustules => nodules

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19
Q

True or False: S. aureus is NF of the skin and nares that can cause skin infection by gaining entry to breaks in skin

A

True

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20
Q

True or False: S. aureus is gram negative cocci, as well as catalase and coagulase (-).

When plated on blood agar, it is beta-hemolytic

A

False - while S. aureus is B-hemolytic, it is…
- Gram (+)
- Catalase/Coagulase (+)

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21
Q

True or False: Bound Coagulase causes bacteria to clump together while Free Coagulase causes a protective fibrin clot to form around bacteria

A

True

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22
Q

S. aureus can cause either: Non-Toxic Mediated Diseases (4) or Toxin Mediated Diseases (2)

List them

A

Non-Toxic Mediated Diseases
1. Folliculitis
2. Furuncles
3. Carbuncles
4. Epidemic Impetigo

Toxin Mediated Diseases
1. Bullous Impetigo
2. SSSS (Staphylococcal Scalded Skin Syndrome)

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23
Q

True or False: Bullous Impetigo is described as a toxemia from focal infection that is usually not necessary at the skin

A

False - this describes SSSS

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24
Q

True or False: SSSS is describe as a toxin made by pyodermic infection at the same focal infection; it is NOT toxemia!!

A

False - this describes Bullous Impetigo

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25
Q

True or False: Folliculitis, Furuncles, Carbuncles, and Epidemic Impetigo are all contagious

A

True
- A person exposed to a lesion will be colonized with virulent strain but will not necessarily develop disease

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26
Q

How do carbuncles develop?
A. Folliculitis => Carbuncle
B. Folliculitis => Furuncle => Carbuncle

A

B. Folliculitis => Furuncle => Carbuncle

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27
Q

____: Superficial infection of an individual hair follicle and apocrine region
A. Folliculitis
B. Furuncles
C. Carbuncles
D. Epidemic Impetigo

A

A. Folliculitis

  • Can occur on any hair bearing site on the body!
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28
Q

An infection of hair follicle and subcutaneous tissue suggests which Non-Toxic Mediated Disease/s?
A. Folliculitis
B. Furuncles
C. Carbuncles
D. Epidemic Impetigo

A

B. Furuncles
C. Carbuncles

Ages 3-15

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29
Q

____: An infection of INDIVIDUAL hair follicle that is associated with lesions that are necrotic, pyogenic abscesses. There are NO systemic signs!!!
A. Folliculitis
B. Furuncles
C. Carbuncles
D. Epidemic Impetigo

A

B. Furuncles

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30
Q

____: An infection of SEVERAL hair follicles that lead to lesions. There are systemic signs of FEVER and malaise!!
A. Folliculitis
B. Furuncles
C. Carbuncles
D. Epidemic Impetigo

A

C. Carbuncles

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31
Q
A
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32
Q

Which layer of the skin does cellulitis affect?
A. Stratum corneum
B. Dermis
C. Epidermis
D. Fat

A

D. Fat

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33
Q

Which layer of the skin does Erysipelas affect?
A. Stratum corneum
B. Dermis
C. Epidermis
D. Fat

A

B. Dermis

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34
Q

Which layer of the skin does Ecthyma affect?
A. Stratum corneum
B. Dermis
C. Epidermis
D. Fat

A

C. Epidermis

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35
Q

Which layer of the skin does Impetigo affect?
A. Stratum corneum
B. Dermis
C. Epidermis
D. Fat

A

A. Stratum corneum

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36
Q

____: Contagious superficial bacterial infection observed mostly frequently in children
A. Folliculitis
B. Furuncles
C. Carbuncles
D. Impetigo

A

D. Impetigo

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37
Q

What is the difference between Nonbullous Impetigo vs. Bullous Impetigo?

A

Nonbullous Impetigo
- Non-toxin

Bullous Impetigo
- Toxin mediated

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38
Q

Classic Nonbullous Impetigo (Epidemic Impetigo) is caused by which two agents?

A
  • S. aureus
  • S. pyogenes
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39
Q

_____: common infectious disease in kids (2-5 years old). Auto-inoculation causes spread.
A. Nonbullous Impetigo
B. Bullous Impetigo
C. Epidemic Impetigo (Classic Nonbullous Impetigo)

A

C. Epidemic Impetigo (Classic Nonbullous Impetigo)

40
Q

In what case will classic nonbullous impetigo NOT scar?

A

If lesion occurs in superficial epidermis

41
Q

True or False: Systemic symptoms are usually present in Classic Nonbullous Impetigo and not contagious

A

False - systemic symptoms are NOT usually present and IS contagious!

42
Q

How does Classic Nonbullous Impetigo occur? Where?

A

Where - superficial epidermis

How - small vesicles forms => pustule forms and ruptures => thick, amber colored crest

43
Q

Pathology of toxin mediated diseases of S. aureus is caused by an infection with a strain that produces sufficient quantities of ETA/ETB, also known as….

A

Exfoliatin Exotoxin (ETA/ETB)

44
Q

What signs + symptoms are associated with ETA/ETB?

A
  1. Epidermal Necrosis
  2. Desquamination/Exfoliation of Intra-Epidermal Layers of skin produce….

A. Epidermal Necrosis
B. Painful bullae => rupture => denuded skin
C. Both

45
Q

____: Toxin associated with ETA/ETB, which splits the intracellular bridges in the stratum granulosum of epidermis

A

Exfoliative Toxin

46
Q

The lesions of Bullous Impetigo contain ___-producing strains of S. aureus

A

exfoliatin toxin (ET)

47
Q

What causes the lesion in Bullous Impetigo?

Do toxin and agent disseminate?

A

1) The toxin
2) No !

48
Q

Which of the Toxin Mediated Diseases is associated with dissemination of exfoliatin exotoxin but NOT the dissemination of S. aureus?
A. Bullous Impetigo
B. Ritter’s
C. SSSS

A

C. SSSS

49
Q

True or False: In both SSSS and Bullous Impetigo, the toxin causes the bullae.

A

False -
SSSS: Toxin causes STERILE BULLAE

Bullous Impetigo: Toxin causes LESION

50
Q

True or False: SSSS is usually a SINGLE, focal infection by strains of S. aureus that produces sufficient ETA and ETB + it IS CONTAGIOUS (!!!)

A

True

51
Q

How do you differentiate between SSSS and Bullous Impetigo?

A

No bacteria/growth = SSSS

52
Q

_____: Most severe form of SSSS + same manifestations

A

Ritter’s Disease of the Newborn

53
Q

S. Pyogenes is GAS (group A strep), as well as:
- Gram (+) or (-)?
- Shape?
- B-hemolytic?
- Sensitive/insensitive bacitracin?

A
  • Gram (+)
  • Chain forming cocci
  • B-hemolytic
  • Bacitracin sensitive
54
Q

Which pathogen is sensitive to bacitracin?
A. S. aureus
B. Staphylococcus
C. S. pyogenes
D. Cutibacterium acnes

A

C. S. pyogenes

55
Q

Which pathogen can give rise to: 1) Epidemic Impetigo / 2) Cellulitis / 3) Scarlet Fever?
A. S. aureus
B. Staphylococcus
C. S. pyogenes
D. Cutibacterium acnes

A

C. S. pyogenes

56
Q

___ is a form of cellulitis associated with blocked lymphatics

A

Cellulitis

57
Q

A patient is infected with S. pyogenes and develops Epidemic Impetigo. Following this, the patient begins have difficulties with urination. What complication may have arisen?

A

Acute Glomerulonephritis

58
Q

True or False: Impetigo due to S. pyogenes infection is unrelated to pharyngeal streptococcal infections

A

True

59
Q

Which of the following can be caused by GAS strains that are lysogenized thus these strains are capable of elaborating SPE (streptococcal pyrogenic exotoxin)?
A. Epidemic Impetigo
B. Cellulitis
C. Scarlet Fever

A

C. Scarlet Fever

  • transduction
60
Q

True or False: Streptococcal pyrogenic exotoxin (SPE’s) that associated with Scarlet Fever are superantigens (Type 1) and potent immunomodulators

A

True

61
Q

True or False: Scarlet Fever is NOT a complication of either GAS Pharyngitis or GAS Impetigo

A

False - Scarlet Fever IS a complication of either GAS Pharyngitis or GAS Impetigo

62
Q

Scarlet Fever can arise as a result of which two conditions?

A

Impetigo and Pharyngitis

63
Q

True or False: Scarlet Fever is associated with systemic signs

A

True - because SPE is a potent immunomodulator

64
Q

____, a hyperemia, is associated with Scarlet Fever
A. Enanthem
B. Exanthem

A

A. Enanthem

65
Q

What is the progression of Enanthem, as seen in Scarlet Fever?

A

White strawberry tongue => red strawberry tongue => red rasberry tongue

Note: can occur in any mucus membrane

66
Q

Scarlet Fever is associated with ____, a scarlatiniform (sandpaper-like rash) that first appears on the TRUNK then spreads PERIPHERALLY to cover whole body.
A. Enanthem
B. Exanthem

A

B. Exanthem

67
Q

True or False: Enanthem is associated with Pastia’s bleeding lines in folds of skin

A

False - this is the case with Exanthem

68
Q

How does Exanthem (rash) resolve?

A

Desquamation!!!
- of sheets of skin (palms and soles)
- occurs 1-2 weeks s/p onset of illness

69
Q

What are complications of Scarlet Fever/Exanthem?

A
  1. Rheumatic Fever
  2. AGN (acute glomerular nephritis)
70
Q

____ is associated with honey erosions or vesicles

___ is associated with red, tender plaque

____ is associated with tender, red plaque with SHARP borders

A
  • Impetigo
  • Cellulitis
  • Erysipelas
71
Q

True or False: Cellulitis can be caused by gram (+) or gram (-) cocci

A

False - can be caused by gram (+) cocci or gram (-) rods

72
Q

True or False: Both facultative anaerobes + obligate anaerobes—which are Gram (-) Rods—can cause Cellulitis

A

True

73
Q

Which three Gram (+) cocci can cause cellulitis?

A
  1. S. pyogenes (GAS)
  2. S. aureus
  3. S. pneumoniae
74
Q

In Cellulitis, Necrotizing Skin Lesions are caused by which three atypical mycobacteria?

A
  1. Mycobacterium ulcerans (Bruruli Ulcer)
  2. Mycobacterium marinum
  3. M. fortuitum
75
Q

Exposure to water (freshwater or seawater) predisposes one to cellulitis with ____ as a common complication

A

bacteremia

76
Q

Exposure to water (freshwater or seawater) predisposes one to cellulitis, which are caused by which three groups of bacteria?

A
  1. Facultative anaerobic; Gram (-) Rods
  2. Atypical Mycobacterium
  3. Vibrio Vulnificus (salt water)
77
Q

Anaerobic Gram (-) Rods AND
Facultative, Anaerobic, Gram (-) Rods from animal bite can cause cellulitis.

Which pathogens in particular (3)?

A

Facultative, Anaerobic, Gram (-) Rods
- P. pestis and multocida
- C. canimorsus

78
Q

True or False: If an animal bites you and you develop cellulitis, it may be due to a gram (+) cocci or diptheroid

A

True

79
Q

True or False: NF of mucosal surfaces, gram (-) rods, and facultative anaerobes are often caused by E. corrodens

A

True

80
Q

Infections detected within 72 hrs after surgery is most likely due to:
A. Staphylococci
B. S. aureus
C. B-hemolytic streptococci
D. C. perfringens
E. Enterococci

A

B. S. aureus
C. B-hemolytic streptococci
D. C. perfringens

81
Q

Post-op infections detected 10-30 days (most common) is most apt due to:
A. Gram (-) Rods
B. Gram (+) Cocci - strep, staphylo, entero
C. S. aureus
D. Enterococci

A

A. Gram (-) Rods
B. Gram (+) Cocci - strep, staphylo, entero

82
Q

True or False: Post-op wound infections detected within 2-3 months could be caused by diptheroids/staphylococci that is Coagulase (-)

Note: more prone if you have prostheses

A

True

83
Q

___: Infections of skin (deep dermis) and may also involve SC fat

A

Cellulitis

84
Q

True or False: Cellulitis develops within a few days and has both local inflammation and systemic signs (fever!!!!!!)

A

True

85
Q

If there is a lesion that appears to be inflammed, may/may not be elevated, and is NOT sharply demarcated, what condition is like likely to be?

A

Cellulitis

86
Q

True or False: Sharply demarcated edge of a lesion suggests erysipelas

A

True

87
Q

True or False: Cellulitis may be accompanied by abscess, necrosis of overlaying skin => suppurative lesions

A

True

88
Q

How is cellulitis treated?

A

Anti-microbial

89
Q

Erysipelas, a specific form of cellulitis that may NOT include SC tissues and DOES include cutaneous lymphatics, is also known as…

A

St. Anthony’s Fire

90
Q

Etiologic agent that causes St. Anthony’s Fire

A

Erysipelas

91
Q

Recurrent St. Anthony’s Fire suggests?

A

Lymphatic blockage

92
Q

How do the clinical manifestations of St. Anthony’s differ from regular cellulitis?

A

In St. Anthony’s Fire…
1) Illness starts w/ systemic signs - burn, itch
2) Then: rapidly spreading erythema forms
- RAISED BORDER - sharply demarcated
- Indurated

93
Q

What’s the difference between aerotolerant/facultative anaerobe vs. obligate aerobe

A
94
Q

Anaerobes are the predominant NF in the ___, __, and ___

A

mouth (gingiva); GI (colon); female genital tract

95
Q

True or False: Anaerobes are commonly weak pathogen and usually a result of endogenous strains

A

True

96
Q

True or False: Poor blood supply + Tissue necrosis can lead to Anaerobic Infections

A

Tru

Medical Microbiology (31 decks)

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