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Q3 Microbiology Final > Bacterial Skin (lec 22) > Flashcards

Bacterial Skin (lec 22) Flashcards

1
Q

Routes of infection?

A

1) Exogenous (disrupt skin barrier)
2) Endogenous (seeded into tissue by blood/lymph)
3) Toxin Induced (made at distant site, cause pathogenesis at/near skin)

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2
Q

Abscess-Forming infections? (3)

A

Acne
Folliculitis
Furuncles/Carbuncles

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3
Q

Acne Vulgaris etiology?

A

Propionibacterium acnes

G+
Anaerobe
Non-motile

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4
Q

Factors contributing to Acne? (4)

A

1) Genetics
2) Follicular epidermal hyperproliferation from androgens
3) Excess sebum prdxn
4) P. acnes prdxn of lipase causes inflammation

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5
Q

Noninflamm Acne Vulgaris caused by?

A

Formation of Microcomedo:

partial obstruction of follicle by sebum, keratinocytes, hair

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6
Q

Noninflam Acne Vulg presents as? (2)

A

1) Closed comedones (whiteheads)

2) Open comedones (blackheads)

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7
Q

Inflamm Acne Vulgaris caused by?

A

Rupture of follicular content into dermis

Nodular is most severe

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8
Q

Folliculitis is?

A

Superficial: small papules/pustules on erythematous base, pierced by central hair

Deep: erythematous nodules

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9
Q

Superficial Folliculitis caused by?

A

S. aureus

P. aeruginosa

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10
Q

S aureus presents as what forms of folliculitis?

A

Impetigo of Bockhart (bearded area)

Sty (eyelid)

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11
Q

P. aeruginosa presents as what form of folliculitis?

A

Hot tub/wetsuit
from contaminated H2O
breakout in swimsuit areas

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12
Q

Furuncles are?

A

Boils/large folliculitis abscess
Extend thru dermis/subQ
Face/neck, thighs/butt

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13
Q

Carbuncles are?

A

Inflamm of many hair follicles
Into dermis/subQ
Neck, back, thighs

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14
Q

Spreading Soft Tissue infections include?

A

Impetigo

Cellulitis

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15
Q

Nonbullous Impetigo caused by?

a/w?

A

S. aureus
S. pyogenes (GAS)

a/w acute glomerulonephritis

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16
Q

Impetigo Pyoderma caused by?

Epidemiology?

A

strep strains

1-5 yo
warm/moist weather

17
Q

Pyoderma infection characteristics?

A

Intradermal vesicles
Honey crusting
Contagious vesicles

18
Q

Bullous Impetigo caused by?

A

S. aureus exfoliatin toxin

digests epiderm

19
Q

Bullous Impetigo presentation?

A

Large, superficial, thin-walled blisters

Crust when burst
Contagious bullae (microbe and toxin in blister, not systemic)
20
Q

Cellulitis is?

caused by?

A

subQ CT infection from toxins/inflamm response

S. aureus/S. pyogenes

(P) G- acinetobacter (trauma), pasturella (cat/dog), aeromonas (fresh H2O), vibrio (salt H2O)

21
Q

Cellulitis presentation?

A

Break in infected skin -> seeding

Acute inflamm subQ CT into lower dermis
Few microbes

Heat, Erythema, Edema, Tenderness (HEET),
“sunburn” diffuse borders

22
Q

Cellulitis labs when?

What tests?

A

Only if:
immunocompromised, skin lesions, large area, spreading

Cx
Imaging to r/o necrotizing fasciitis

23
Q

Cellulitis tx?

A

elevation
ABX
No NSAIDS (mask indicators, ↓ immune response)

24
Q

Necrotizing Fasciitis caused by?

A

Type 1: > 1 faculative aerobe and anaerobe

Type 2: Flesh-eating Group A strep pyogenes

25
Q

Necrotizing Fasciitis Type 1 risk factors?

A

↓ immune, DM, surgery

26
Q

Necrotizing Fasciitis Type 2 risk factors?

A

Anyone

27
Q

Necrotizing Fasciitis infection route?

A

deeper tissues -> subQ, muscle fascia

spreads along mm fascia (poor bloody supply)
mm spared (good blood supply)
28
Q

Necrotizing Fasciitis presentation?

A

Acute onset HEET, shiny
↑↑ pain
↑↑ progression
red/purple -> cutaneous anesthesia (dead bv/nn) -> blue/gray
FAILURE TO RESPOND TO ABX (poor blood source = poor delivery)

29
Q

Necrotizing Fasciitis advanced infection presentation?

A

fever, tachy, toxicity (confused)

putrid if type 1 anaerobe

30
Q

Necrotizing Fasciitis presentation w/ surgery?

A

swollen/gray fascia,
thin, brown exudate
extensive undermining,
tissue separates along fascial planes

31
Q

Necrotizing Fasciitis diagnostics?

A

Surgical
Gram stain/Cx/Rapid strep
MRI (extent of inf)

32
Q

Necrotizing Fasciitis tx?

A

debridement
ABX
HB O2 (kills anaerobes)
Maggots

33
Q

Myonecrosis/Gas gangrene caused by?

A

C. perfringens A
G variable in wound
Spores
Anaerobe

34
Q

C. perfringens virulence factor?

Route of infection?

A

α toxin phospholipase C (cytolytic)

Reduced O2 tension (trauma/microbes) -> Anaerobic cells/spores produce exotoxin/H2 gas

35
Q

Myonecrosis presentation?

A

EMERGENCY
Rapid onset of pain
Skin pale -> bronze -> edema -> bullae

Exudate smells sweet (foul = Ø c. perf)

Fever, tachy, confusion

36
Q

Myonecrosis diagnostics?

A

Bx

Stain = mm necrosis, variable G, Ø PMN

37
Q

Myonecrosis tx?

A

debridement
HBO2
ABX

Q3 Microbiology Final (8 decks)

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