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FoundSci III > Bacterial Skin Infections I > Flashcards

Bacterial Skin Infections I Flashcards

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1
Q

What are the risk factors for S. aureus?

A

Diabetes

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2
Q

What are the risk factors for P. aeruginosa?

A

Neutropenia
Hot tub exposure
IV drug abuse

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3
Q

What are the risk factors for MRSA?

A

IV drug abuse

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4
Q

How do you treat a purulent SSTI?

A

Incision/Drainage along with culture/sensitivity if moderate to severe

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5
Q

How do you treat an SSTI that is non-purulent?

A

Empiric RX in mild to moderate

Severe is do everything that can be done

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6
Q

What are the characteristics of Staphylococci?

A

Gram +
Facultative anaerobe
Grape-like clusters
Catalase +
Beta hemolytic

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7
Q

Where is Staphylococci found? How is it spread?

A

On skin and mucus membranes of humans

Nasal shedding

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8
Q

What does Staphylococcus aureus look like when grown?

A

White/Golden colonies

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9
Q

What are the virulence factors of S. aureus? x3

A
  1. Protein A
  2. Cytotoxins (alpha) and exfoliative toxins
  3. Coagulase
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10
Q

What does protein A do for S. aureus?

A

Binds to IgG FC domain - inhibits phagocytosis and antibody functionality

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11
Q

________ of S. aureus is a pore-forming cytotoxin.

A

Alpha-toxin

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12
Q

What are the 2 exfoliative toxins?

A

Exfoliative toxin A (ETA)

Exfoliative toxin B (ETB)

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13
Q

___________ of S. aureus are serine proteases that cleave the intercellular bridges (desmoglein-1) in the epidermis.

A

Exfoliative toxins

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14
Q

Exfoliative toxins mediate ________ and ________

A

scalded skin syndrome

bullous impetigo

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15
Q

___________ of S. aureus converts fibrinogen to fibrin. Promotes abscess formation and persistence. Escape phagocytic clearance.

A

Coagulase

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16
Q

What diseases does S. aureus cause? x8

A
  1. Impetigo (bullous and non-bullous)
  2. Scalded Skin Syndrome
  3. Folliculitis
  4. Furuncles and Carbuncles
  5. Cellulitis
  6. Osteomyelitis
  7. Septic arthritis
  8. Paronychia
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17
Q

How would you diagnose S. aureus?

A

Beta-hemolytic
Gram stain +
Catalase and coagulase +
Antibiotic susceptibility

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18
Q

What are the resistance and resistance mechanism for Methicillin Sensitive S. aureus (MSSA)?

A

Resistant to some beta-lactams but not all

Efflux pumps, beta-lactamase(s), altered porins

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19
Q

What are the resistance and resistance mechanism for Methicillin Resistant S. aureus (MRSA)?

A

Resistant to all known beta-lactams

mecA gene encoding transpeptidase/PBP with low affinity for beta-lactams

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20
Q

What are the characteristics of Streptococcus pyogenes?

A

Gram + cocci in chains
Catalase -
Beta hemolytic
Bacitracin sensitive
Group A strep or GAS - Lancefield group A carbohydrate cell wall Ag

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21
Q

What diseases does Strep. pyogenes cause? x5

A

Non-bullous impetigo
Erysipelas
Cellulitis
Osteomyelitis
Necrotizing soft tissue infections

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22
Q

What is the sequelae of S. pyogenes?

A

Associated with GAS skin infections or pharyngitis

Post-streptococcal glomerulonephritis

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23
Q

What is the capsule of GAS made up (Group A Strep)?

A

Hyaluronic acid

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24
Q

__________ of GAS helps anchor in cell wall and binds fibronectin and other host surface molecules.

A

M protein

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25
What are the toxins of GAS?
Streptococcal pyrogenic exotoxins - SpeA
26
_______ of GAS is a superantigen and linked to ___________
SpeA Scarlet fever, streptococcal toxic shock syndrome, and necrotizing fasciitis
27
What are the virulence factors of GAS?
1. Hyaluronic acid capsule 2. M protein adhesin 3. SpeA exotoxin
28
Scarlet fever is often sequelae to ___________. Commonly seen in ________
GAS pharyngitis Children
29
What are the symptoms of Scarlet Fever? x3
1. Rough textured sandpaper rash that blanches under pressure 2. Desquamation 3. Strawberry tongue
30
What is the mechanism of Scarlet Fever?
Systemic dissemination of streptococcal pyrogenic exotoxin (SPEs) No systemic spread of GAS bacteria
31
_____________ is immunologically mediated, nonsuppurative, delayed sequelae post pharyngeal or cutaneous GAS infection.
Acute Post-Streptococcal Glomerulonephritis
32
How does Acute Post-Streptococcal Glomerulonephritis present? x5
1. In kids commonly 2. 3-6 weeks post-GAS cutaneous infection 3. Acute nephritic syndrome - hematuria (brown), proteinuria, hypertension +/- oliguria 4. Edema - face, orbits, extremities 5. No systemic disease symptoms
33
What immune related kidney damage occurs with Acute Post-Streptococcal Glomerulonephritis?
Reduced capillary perfusion and glomerular filtration rate Decreased GFR leads to oliguria, acid base imbalance, electrolyte abnormalities, edema, and hypertension
34
How do you diagnose Acute Post-Streptococcal Glomerulonephritis?
Serology
35
Elevated antibodies to Acute Post-Streptococcal Glomerulonephritis indicate prior exposure via _______ and _______
Pharyngitis Skin infections: Anti-DNAse B
36
What causes Streptococcal Toxic Shock Syndrome?
GAS invasive infection that leads to streptococall pyrogenic exotoxins production Cytokine storm occurs and then TSS
37
How does Streptococcal Toxic Shock Syndrome present?
Hypotension, fever, tachycardia, multi-organ dysfunction
38
How do you diagnose Streptococcal Toxic Shock Syndrome?
Symptoms Isolation of GAS from sterile site Hypotension +/- 2 organs involved
39
Is Strep TSS or Staph TSS invasive?
Strep is invasive
40
Staphylococcal Scalded SKin Syndrome is a systemic manifestation of a _________ S. aureus infection
localized
41
How does Staph. Scalded Skin Syndrome present?
Skin peels off with minimal lateral pressure - Nikolsky sign Shedding of superficial skin layers in large sheets Scalded skin
42
What is the pathogenesis of Staph scalded skin syndrome?
Exfoliative toxins A & B (ETA< ETB)
43
How do you diagnose Staph Scalded Skin Syndrome?
NOT culture - bullae fluid almost always negative with no evidence of leukocytes
44
How do bullae of Bullous Impetigo present?
Filled with cloudy fluid Rupture resulting in erosions and brown crusting Fluid contains S. aureus
45
How does non-bullous impetigo present?
Papules becomes vesicle that then rupture leading to crusting (honey crusts) Highly contagious
46
______ is a non-bullous impetigo that extends into the dermis.
Ecythma
47
How does ecthyma present?
Appears as vesicles and pustules that enlarge, ulcerate, and crust over
48
How do you diagnose impetigo and ecythma?
Symptoms Gram stain and culture of exudate
49
Folliculitis is often _______ associated and caused by _______
Hot tub P. aeruginosa
50
_______ presents as papules and/or pustules within hair follicles and often in crops
Folliculitis
51
Furuncle are deep hair follicle infection that _______
extends into adjacent tissue
52
Carbuncles are when >/+ _________ and _______ and _____ are often present
2 furuncles coalescing Fever and malaise
53
What is cellulitis caused by?
S. pyogenes - more common S. aureus
54
What is cellulitis an infection of?
Dermis and epidermis
55
What are the presentations of cellulitis?
Erythema that quickly progresses to edema, pain/tenderness Poorly defined borders Vesicles, bullae, or bruising
56
Erysipelas is a subclass of cellulitis and often preceded by ________
S. pyogenes respiratory or skin infection
57
________ presents with abrupt onset of intense pain, erythema, and edema. Sharp demarcation with raised borders.
Erysipelas
58
_______ is a local bacterial nail fold infection, sometimes with an abscess
Acute paronychia
59
What bacteria cause Acute Paronychia?
S. aureus, S. pyogenes
60
How does acute paronychia present with?
Presents as pain, erythema, and edema in nail folds
61
What causes chronic pronychia?
C. albicans

FoundSci III (22 decks)

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