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MSK Formative 1 > Infection of Skin and Soft Tissue > Flashcards

Infection of Skin and Soft Tissue Flashcards

1
Q

Staphylococcus aureus causes what 4 skin infections?

A
  1. Folliculities
  2. Furuncles
  3. Toxic shock syndrome
  4. Bacteremia
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2
Q

Streptococcus pyogenes causes which six skin infections?

A
  1. Cellulitis
  2. Lymphangitis
  3. Impetigo
  4. Erysipelas
  5. Necrotizing fasciitis
  6. Toxic shock syndrome
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3
Q

Which enzymes affect spread and multiplication in skin infections?

A
  • Hyaluronidase (spreading factor, Staph and Strep use as toxin)
  • Hemolysins (destroys RBC)
  • Lipases
  • Collagenase
  • Elastases
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4
Q

What are predisposing risk factors to exogenous skin infections from staph or strep?

A
  • Excessive moisture
  • Trauma
  • Introduction of foreign body
  • Pressure
  • Compromised blood supply
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5
Q

What is the skin response to exogenous infections? (3)

A
  1. spreading infections :
    • impetigo- epidermis
    • Erysipelas- dermal lymphatics
    • Cellulitis- subcutaneous fat layer
  2. abscess formation:
    • folliculitis, furuncles/boils
    • carbuncles
  3. necrotizing infection
    • Fasciitis and gas gangrene/myonecrosis
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6
Q

What organism causes gas gangrene?

A

Clostridia

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7
Q

Of staphylococci and streptococci which is catalase +?

A

Staphylococci

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8
Q

Which Staphylococci is coagulase (+) and (-)?

A
  • (+): S. aureus
  • (-):
    • S. epidermidis (novobiacin sensitive)
    • S saprophyticus (novobiacin resistant)
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9
Q
  • Folliculitis is caused by which bacteria?
  • What does it cause?
A
  • Staphyloccocus aureus
    • infects sebaceous glands and hair follicles become inflamed
    • There is an influx of neutrophils
    • fibrin is deposited (site walled off) and an abscess is made
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10
Q

Furuncles/ Carbuncles are abscess is? Caused by what bacteria?

A
  • S. aureus
    • Abscess in subcutaneous tissue
      • Furuncle= single
      • Carbuncle= Multiple, interconnected
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11
Q

Necrotizing fasciitis, myonecrosis and Gangarene are rapidly progressing? What toxin is produced/ which bacteria?

A
  • Rapidly progressing cellulitis
    • extensive necrosis of subcutaneous tissue (acute)
  • Toxin producing Clostridium perfringens and S. pyogenes produce virulence factors (particularly M protein)
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12
Q

Symptoms of Necrotizing Fasciitis?

A

Intense pain, fever inflammation

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13
Q
  • What kind of bacteria is Clostridium perfringens?
  • What toxins does it produce?
A
  • Gram positive bacilli (anaerobic)
    • spore forming
  • Toxins A-E
    • Exotoxins: alpha toxin hydrolyzes cell membranes
    • Phospholipase
    • Hemolysins (destroy RBC)
    • Collagenases
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14
Q

What are 3 cutaneous responses to bacterial toxins?

A
  • Toxic shock syndrome
  • Scalded fever syndrome
  • Scarlet fever
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15
Q

Toxic shock syndrome is caused by which bacteria? MOA?

A
  • Staphylococcus aureus producing toxins
  • Binds to MHC and TCR outside of antigen binding site
    • cause overwhelming release of IL-1,IL-2, INF gamma and TNF alpha
    • —> shock
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16
Q

Symptoms of Toxic Shock syndrome?

A
  • Multisystem involvement: shock, fever, rash
  • desquamation (skin peeling)
  • septicemia (infection in blood)
  • toxemia
17
Q
  • Scalded Skin Syndrome is caused by which bacteria?
  • MOA?
  • Characterized by?
A
  • Staph. aureus
    • exfoliation toxin producing (Exotoxin)
    • exotoxin destroys keratinocyte attachments in stratum granulosum (separation of top layer of epidermis)
  • Characterized by:
    • fever
    • generalized erythematous rash with sloughing of upper layers of epidermis
18
Q
  • Ecthyma gangrenosum causes necrotic skin lesions
    • caused by which type of bacteria?
    • Typically seen in which patients?
    • Toxins produced?
A

Pseudomonas aeruginosae;

  • gram (-) rod that is oxidase positive
    • Opportunist pathogen
      • ​typically seen in immune compromised patients
    • Major nosocomial (in hospital) pathogen has multi drug resistance

Toxins:

  • Endotoxin
  • Exotoxin A (inhibitor of EF in eukaryotic protein synthesis)
  • Extracellular slime Pigments
19
Q

Mycobacteria are what kind of bacteria?

A
  • Gram (+) cell wall
  • Acid fast (mycolic acid)
  • slow growing
20
Q
  • Mycobacterium terberculosis
  • M. marinum
  • M. ulcerans

All cause?

A
  • All cause chronic ulcers
    • ​M. terberculosis= TB
    • M. Marinum= swimming pool
    • M. Ulcerans= in tropical countries
21
Q

Nocardia brasiliensis which is a bacteria that causes chronic ulcers is what kind of bacteria?

A
  • Branching and intracellular opportunist
  • Partial acid fast
  • Beaded gram (+) bacilli
22
Q

Main virulence factosr of Staph. aureus and Strep. pyogenes?

A
  • Strep. pyogenes:
    • M protein
    • exotoxins
    • streptolysins S&O
    • Streptokinas A&B
    • hyaluronidase
  • Staph. aureus:
    • Proteins A
    • Capsule
    • Coagulase
    • Mucopeptide
23
Q
  • Where is the location of beta lactamases in bacteria?
  • How are they resistance to antibiotics like penicillin?
A
  • Beta lactamases are excreted into extracellular space by Gram (+) bacteria and into periplasmic space by gram (-) bacteria
  • beta lactamase enzyme cleaves beta lactam ring rendering antibiotic ineffective
24
Q
  • Subcutaneous tissue connects?
  • Composed of?
A
  • Connects dermis to the deeper fascia
  • has fascial layers (Scarpa’s and Camper’s)
  • Composed of:
    • loose connective tissue
    • stored fat (thickness varies greatly)
  • Contains
    • vessels
    • nerves
    • glands
25
Q

Function of subcutaneous tissue?

A
  • thermoregulation (insulation)
  • provides padding for bony prominences
26
Q

What are two examples of excessive formation of collagen during tissue repair?

A
  1. Hypertrophic scar (raised scar); does NOT extend beyond boundaries of original wound
    • Thermal or traumatic injury involving deep dermis
  2. Keloid (genetic; African Americans)
    • Scar grows beyond boundary of wound

MSK Formative 1 (11 decks)

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