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Derm micro -Saviola Flashcards

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Dermatology Board Prep flashcards
1
Q

What are the 2 most common bacterial causes of skin infections? What are their characteristics?

A

S. aureus=gram + clusters, catalase +, coagulase +, beta hemolytic, mannitol fermenting

S. pyogenes (Group A strep) =gram +, catalase -, beta hemolytic, bacitracin sensitive

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2
Q

What are the 2 main virulence factors of S. aureus that allow for derm infections?

A
  • Panton-valentine leukocidin (PVL)==> gets into host cell membrane and creates a bore and causes the cell to lyse
  • protein A =aggregation ==> evade phagocytosis and important in biofilm formation
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3
Q

What are the 2 main virulence factors of S. progenies (GAS) that allow for derm infections?

A
  • M protein =evade phagocytosis

- Superantigens =streptococcal pyrogenic exotoxins

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4
Q

What is the cause of Acne vulgaris?

A
  • increase in sebum released by sebaceous glands after puberty
  • smal cysts in hair follicles from blockage of orifices by retention of sebum
  • microaerophilic bacteria cause inflammation in the cyst
  • P. acnes produces CAMP factor (acts with S. aureus beta hemolysin to cause cytolysis)
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5
Q

What is erysipelas? What is the most common cause and site of infection?

A
  • type of superficial cellulitis with lymphatic involvement, dermis, and uppermost subcutaneous tissue
  • febrile
  • S. pyogenes
  • face or lower extremities
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6
Q

What bacteria causes Bullous Impetigo? What virulence factor allows this?

A

S. aureus

-Exfoliative toxins (Epidermolytic toxin A and B) cleave desmoglein 1 –> lose adhesiveness —> blister/boil

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7
Q

How is S. aureus typed? How is S. pyogenes typed?

A

S. aureus is typed based on phage

S. pyogenes is typed based on M protein

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8
Q

What causes Staphylococcal Scalded Skin Syndrome?

A
  • S. aureus exfoliative toxin (Epidermolytic toxin A and B)

- enters circulation ==> more wide spread sloughing off than in bullous impetigo

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9
Q

What causes Toxic Shock Syndrome (2)? How? What is the skin rash and desquamation due to?

A
  • S. aureus that produces TSST-1
  • ->superantigen binds to MHC II and T cell receptor nonspecifically ==> activate a lot of T cells

or
-Streptococci producing streptococcal pyrogenic exotoxins (super antigen) and types M1 and M3 may be overrepresented in this disease

-desquamation due to immune reaction damaging the skin

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10
Q

What other serious infections can group A streptococci cause?

A
  • necrotizing fasciitis (pyrogenic exotoxins –> hypotension and death)
  • Scarlet fever (exotoxin mediated)
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11
Q

What are maculopapular rashes generally due to? Are the viruses present in the rash?

A
  • immune response

- viruses not present in the rash

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12
Q

What is measles due to? What is an important complication?

A
  • Paramyxovirus (enveloped - ssRNA virus)
  • rash due to the presence of antibody and immune reaction
  • can cause subacute sclerosing pan encephalitis 6-7 years after disease –> death
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13
Q

What is Rubella?

A

-Togavirus (enveloped + ssRNA)

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14
Q

What virus causes Erythema Infectiosum? Where does this virus replicate?

A

Parvovirus B19

replicated in rapidly dividing erythroid precursors

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15
Q

What causes Roseola infantum? What are the symptoms?

A

HHV6 (large enveloped dsDNA virus)

-3-5 days of high fever followed by a maculopapular rash

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16
Q

Are viruses typically present in the vesicles in vesicular exanthema? What are 3 examples of this?

A

Yes!
(fluid in the vesicle can transmit the virus to others)

  • Varicella -Zoster (chicken pox and shingles)
  • Hand foot and mouth disease
  • Variola (smallpox)
17
Q

What kind of virus causes Varicella-zoster virus?

A
  • herpesviridae family

- enveloped dsDNA virus

18
Q

What virus is a large “brick-shaped” (dumbbell shaped core) virus that replicates in the cytoplasm of the host cell? What type of rash pattern is associated with this?

A
  • Variola (smallpox)
  • centrifugal pattern of rash on extremities
  • high fever
19
Q

How does the rash of Variola (smallpox) differ from that of Varicella (chickenpox)?

A

Variola=centrfugal (on head and extremities more

Varicella=more on chest

20
Q

What causes Hand Foot and Mouth disease? How is this transmitted?

A
  • Coxsackie A virus (Picornavirus)

- fecal oral or respiratory

21
Q

Which 3 viruses infect the skin and remain in that local area?

A
  • Herpes simplex virus
  • Human papilloma virus (naked icosahedral dsDNA)
  • Molluscum contagiousum
22
Q

What do the the lesions of Molluscum contagiousum virus look like?

A
  • smooth firm shiny flesh colored to pearly white hemispheric papules with umbilicated (indented) centers
  • confined to the skin and mucous membranes.
  • Pox family virus
  • seen in kids and wrestlers a lot
23
Q

What form do dimorphic fungi take in the environment? In human tissue?

A

environment=mold

body=yeast

24
Q

What component of fungal membranes is different from human cell membranes? What is their cell wall made of?

A
  • fungi have Ergosterol in their membranes

- cell wall contains chitin, glucan and mannoproteins (no peptidoglycan)

25
Q

What test should be used to look for fungi?

A

KOH prep

26
Q

Where are superficial mycoses found? Do they cause much inflammation? What are some examples? (2)

A
  • limited to the outermost (cornified) layers of the skin and hair.
  • no inflammation
  • Pityriasis Versicolor (spaghetti and meatballs)
  • Tinea nigra
27
Q

Where are cutaneous mycoses found? What is another name for these? What do these organisms normally express? What are some examples?

A
  • Dermatophytes
  • infections that are deeper in the epidermis, hair, and nails but restricted to the keratinized layers of the skin.
  • express keratinases that break down keratin
  • Tinea capitis, tinea manus, tinea unguium, tinea corporis
  • tinea pedia (athletes foot)
  • tinea cruris (jock itch)
28
Q

Where are subcutaneous mycoses found? What is an example of this? How does it spread?

A
  • involving the dermis, subcutaneous tissues, muscle and fascia
  • Sporotrichosis (dimorphic fungus)
  • spreads through lymphatics

Derm (19 decks)

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