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Microbiology > E2- Bacterial Skin Infection > Flashcards

E2- Bacterial Skin Infection Flashcards

1
Q

What kind of infections raise concerns over colonization with resistant bacterial or underlying issees?

A

Recurrent infections

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2
Q

What bacteria is apart of normal skin and mucous membrane inhabitants and is often introduced through breaks in skin?

A

Staphylococci
(inoculum is usually not large, meaning proper cleansing and disinfection with germicidal soap or other agents will prevent disease in persons of normal health)

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3
Q

If a foreign body is present (splinter, stitches, surgery) what does this mean for probability of infection?

A

Infectious dose drops dramatically (takes less bacteria to cause an infection, because the bacteria can hide better)

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4
Q

What is a disease of sebaceous follicles and is a noninfectious form of folliculitis?

A

Acne Vulgaris

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5
Q

What can trigger acne vulgaris?

A

Androgen hormones

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6
Q

Is Propionibacterium acne gram positive/negative? Shape? Oxygen tolerance?

A

Gram positive anaerobic rod (normal skin flora)

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7
Q

When does inflammatory acne vulgaris develop?

A

Develops when follicular contents rupture into the dermis

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8
Q

What is primary causative agent of Folliculitis?

A

Staph. aureus (majority of abscess-type infections)

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9
Q

What causes mild pain, itching/irritation with pustules or nodules surrounding hair follicles?

A

Folliculitis

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10
Q

What should you do if 1st line treatments are not working for tx of Folliculitis?

A

Gram stain to rule or gram- negative etiology or MRSA

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11
Q

What is secondary causative agent of Folliculitis?

A

Pseudomonas aeruginosa

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12
Q

Is Staph. aureus gram positive/negative? Shape?

A

Gram positive cocci

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13
Q

Is Pseudomonas aeruginosa gram positive/negative? Shape?

A

Gram negative rod

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14
Q

Where are Pseudomonas aeruginosa infections commonly acquired? How does t appear?

A

Hot tubs

Itchy maculopapular rash, some pustules

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15
Q

What is the causative agent of most furuncles?

A

Staph. aureus

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16
Q

What is an accesses that involves a hair follicle and surrounding tissue?

A

Furuncle (boil)

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17
Q

What is a cluster of furuncles with subcutaneous connections, that extend into dermis and subcutaneous tissue?

A

Carbuncle

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18
Q

Can furuncles or carbuncles cause systemic effects like fever and prostrations (exhaustion)?

A

Carbuncle

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19
Q

What populations commonly get furuncles/carbuncles?

A

Obese, immunocompromised, diabetic and elderly

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20
Q

How are furuncles and carbuncles treated?

A

Abscesses are incised and drained
Hot compresses
Abx if > 5 mm, do not resolve with drainage, on evidence of spreading, or occur in immunocompromised or subjects at risk of endocarditis

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21
Q

What kind of abx should you use to tx furuncles or carbuncles?

A

Use antibiotics that are effective against MRSA

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22
Q

What kind of abx should you use to tx furuncles or carbuncles if pt has fever or multiple abscesses?

A

Aggressive combination therapy with rifampin

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23
Q

How can you prevent recurrent furuncles?

A

Liquid soap containing chlorhexidine/isopropyl alcohol and maintenance antibiotics.

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24
Q

What is a superficial skin infection with crusting or bullae?

A

Impetigo (Pyoderma)

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25
Q

What causes Impetigo (Pyoderma)?

A

Staphylococci, streptococci or both.

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26
Q

What is severe form of impetigo featuring deep invasion of dermis caused by same agent producing non-bullous impetigo?

A

Ecthyma

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27
Q

What are risk factors for Impetigo and Ecthyma?

A

Moist environment, poor hygiene or chronic nasopharyngeal carriage of agents

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28
Q

What is the most common cause of non-bollous impetigo?

A

S. aureus - currently #1 cause, with MRSA in about 20% of recent cases

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29
Q

What is often co-infected with S. aureus impetigo?

A

Streptococcus pyogenes – (group B, β-hemolytic)

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30
Q

What are vesicles that enlarge to form bacteria-colonized fluid-filled bullae created by action of exfoliative toxin that disrupts epidermal cell connections?

A

Bullous Impetigo

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31
Q

What is another name for Staphylococcal Scalded Skin Syndrome?

A

Ritter’s Disease

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32
Q

What is an acute and extensive epidermolysis due to action of staphylococcal toxin (exfoliatin) that splits the skin just beneath the granule cell layer?

A

Staphylococcal Scalded Skin Syndrome

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33
Q

What is unique about the bullae in Staphylococcal Scalded Skin Syndrome?

A

Bullae are sterile – no bacteria or leukocytes, this is due to toxin

34
Q

Staphylococcal Scalded Skin Syndrome is positive for what sign?

A

Positive Nikolsky’s sign, skin peels easily, desquamated areas look scalded

35
Q

What are acute bacterial infections of the skin and (sometimes) deeper subcutaneous tissues?

A

Erysipelas and cellulitis

36
Q

What is superficial cellulitis with focal dermal lymphatic involvement? What are the causative agents?

A

Erysipelas

Group A Streptococcus pyogenes

37
Q

What is another name for erysipelas?

A

St. Anthony’s Fire

38
Q

Patient presents with Erythematous, raised lesions with distinct borders (demarcation), rash, lymphadenopathy, fever, and chills. What do you suspect?

A

Erysipelas (St. Anthony’s Fire)

39
Q

What is a unilateral infection involving deeper dermis and subcutaneous tissues?

A

Cellulitis

40
Q

Patient presents with areas of heat, erythema, edema, and tenderness (HEET) unilaterally on the lower leg, localized sunburn-like area with indistinct borders that blend in elevation and color to surrounding tissue. What do you suspect?

A

Cellulitis - Wound may not be evident

41
Q

What are the causative agents of cellulitis?

A

S. aureus and S. pyogenes

42
Q

What should you avoid in the tx of cellulitis?

A

NSAIDS – may mask pain of developing myonecrosis and interfere with response to agent

43
Q

Why do cultures rarely ID the pathogen in cellulitis infection?

A

Too many options to test for

44
Q

Besides the major two, what are other agents known to produce cellulitis?

A 
Acinetobacter baumannii
Pasteurella multocida
Capnocytphaga species 
Aeromonas hydrophilia
Vibrio vulnificus
45
Q

What pathogen is associated with cat bite infections?

A

Pasteurella multocida

46
Q

What pathogen is associated with cuts from an oyster or salt water injury?

A

Vibrio vulnificus

47
Q

What are signs of MRSA infection?

A 
Redness, swelling, warmth, pain with:
Fluctuance
Yellow or white center
Central point (head)
Draining pus or ability to aspirate pus with syringe
48
Q

How is MRSA dx?

A

PCR assay to detect mecA gene or latex agglutination assay

49
Q

What part of the body do necrotizing infections affect?

A

Subcutaneous tissue, fascia, and/or muscle

50
Q

How does Necrotizing fasciitis present?

A 
HEET
Pain out of proportion*
Rapid progression over several days
Skin changes color (red-purple to patches of blue-gray)
Thick pink/purple fluid fulled bullae
Cutaneous anesthesia
51
Q

What makes dx of necrotizing fasciitis difficult?

A

Initially overlying tissue appears unaffected

Makes diagnosis difficult without surgical intervention

52
Q

What will determine blood supply in a necrotizing fasciitis infection?

A

Involvement of muscle tissue

53
Q

What type of Necrotizing fasciitis is most common? How is it characterized?

A

Type 1

Polymicrobic, one anaerobe plus one facultative anaerobe or aerobe

54
Q

What is a major risk factor for Type 1 necrotizing fasciitis?

A

Diabetes

55
Q

What is the mildest form of acne vulgaris that forms small firm pink bumps?

A

Papules

56
Q

What form of acne vulgaris is clearly inflamed and contains visbable pus?

A

Pustule

57
Q

What form of acne vulgaris is large, painful, inflamed, pus-filled lodged deep within the skin?

A

Nodule- most severe form

58
Q

How should you treat extensive scalded skin syndrome? Does this syndrome have high or low mortality rates?

A

Treat as for burns

Mortality rate is low and often due to secondary infections

59
Q

What type of Necrotizing fasciitis is “flesh-eating?”

A

Type 2

60
Q

What is the causative agent of Type 2 Necrotizing fasciitis?

A

Group A Strep (monomicrobic)

61
Q

How does the fascia present in Necrotizing fasciitis? Is there pus?

A

Fascia appears swollen and dull gray

No true pus anywhere, only thin brownish excudate

62
Q

What differentiates Necrotizing fasciitis from Cellulitis?

A

Failure to respond to abx therapy

Cellulitis will typically respond in 24-48 hrs

63
Q

What is another name for Clostridal myonecrosis?

A

Gas gangrene

64
Q

What are the majority of Gas gangrene cases caused by?

A

Clostridium perfiringens type A

65
Q

What type of organism is Clostridium perfiringens type A?

A

Spore forming, gram positive anaerobic bacillus

66
Q

In a Gas gangrene infection, what promotes split and invasion of nearby tissue?

A

Production of exotoxins and insoluble H2 gas

67
Q

Patient presents with rapid onset of pain. The skin has a bronze appearance, tense edema, is intensely tender, and crepitant. There is overlying bullae. What do you suspect?

A

Gas gangrene

68
Q

How is Gas gangrene dx?

A

Tissue biopsy and presentation

** biopsy gram stain will show muscle necrosis, gram-variable rods, and tissue destruction

69
Q

What is shown on a gram stain of a Gas gangrene tissue biopsy?

A

Muscle necrosis

Gram-variable rods and tissue destruction

70
Q

What are the two causative agents of Toxic Shock Syndrome?

A

Staph aureus and Strep pyogenes

71
Q

Patient presents with soft tissue inflammation at the site of skin infection that leads to bacteremia and necrotizing fasciitis. What do you suspect?

A

Streptococcal Toxic Shock Syndrome

72
Q

What pathogen is responsible for toxic shock syndrome associated with tampon use?

A

Staphylococcus aureus

73
Q

What triggers the immune response in toxic shock syndrome?

A

Non-specific binding of toxin to receptors

74
Q

What treatment is usually sufficient for folliculitis?

A

Topical Clindamycin ointment or Benzoyl peroxide wash

75
Q

What is the management of scalded skin syndrome?

A

Prompt diagnosis and therapy with penicillinase-resistant anti-staph antibiotics.

76
Q

What is the treatment of erisepelas?

A

Oral or IV antibiotics targeted against the most likely agent

77
Q

Is the treatment for cellulitis?

A

Empiric Abx treatment, but be aware infections may be mixed etiology

78
Q

What is the causative agent of Type 1 necrotizing fasciitis?

A

Group A strep (pyogenes) and anaerobes

79
Q

What is the treatment for necrotizing fasciitis?

A
  • Surgical debridement
  • Amputation
  • IV antibiotics
80
Q

What is the common way to get gas gangrene?

A

Direct introduction of anaerobic cells or spores into a wound

81
Q

How is gas gangrene treated?

A

IV antibiotics, hyperbaric oxygen therapy, and surgical debridement/amputation

*** on surgery, infected muscle wil be dark red/black, noncontactile, and will not bleed

Microbiology (23 decks)

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