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Q5 Dermatology > Bacterial Skin Infections > Flashcards

Bacterial Skin Infections Flashcards

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Dermatology Board Prep flashcards
1
Q

Cellulitis: prevalence

A

very common infection

occurs in up to 3% of ppl per year

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2
Q

Cellulitis:
results from what?
presents how?
more commonly found where?

A

results from infection of dermis, (U) enters through a wound, insect bite or fungal infection (e.g. tinea pedis)

spreading erythematous, non-fluctuant tender plaque

more (C) found on LOWER LEG

streaks of lymphangitis may spread from the area to the draining of lymph nodes

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3
Q

risk factors for cellulitis (5)

A
  1. local trauma (bug bites, laceration, abrasion, puncture wound)
  2. underlying skin lesion (furuncle, ulcer)
  3. inflammation (local dermatitis, radiation tx)
  4. pre-existing skin infection (impetigo, tinea pedis)
  5. 2* cellulitis from blood-born spread of infection, or from direct spread of subadjacent infections (fistula from osteomyelitis) is rare
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4
Q

Cellulitis etiology

A

80%: GRAM POSITIVE

group A strep & staph aureus are most (C) causal pathogens

if unusual exposures (P): Pasteurella multocida (animal bites)
Eikenella corrodens (human bites)
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5
Q

the next best step in management of cellulitis?

A

begin abx immediately w/coverage for gram positive bacteria

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6
Q

un-tx cellulitis may lead to

A

sepsis & death

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7
Q

Tx of outpatients w/nonpurulent cellulitis

A

empirically tx for beta-hemolytic streptococci (group A strep)

(some clinicians choose an agent that is also effective against S. aureus)

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8
Q

Tx of outpatients with purulent cellulitis (purulent drainage or exudate in the absence of a drainable abscess)

A

empirically tx for community-associated MRSA

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9
Q

Tx of cellulitis for unusual exposures

A

cover for additional bacterial species likely to be involved

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10
Q

Cellulitis tx (general)

A

monitor pts closely, revise tx if poor response to initial treatment

elevate the involved area

tx tinea pedis if present

for hospitalized pts: empiric therapy for MRSA should be continued

cultures from abscesses & other purulent Skin & Soft Tissue Infections (SSTIs) are recommended in patients tx with abx therapy

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11
Q

healthcare-associated MRSA (HA-MRSA) & community-acquired MRSA (CA-MRSA) risk factors include: (11)

A
  1. Abx use
  2. prolonged hospitalization
  3. surgical site infection
  4. intensive care
  5. hemodialysis
  6. MRSA colonization
  7. proximity to others w/MRSA colonization or infection
  8. skin trauma
  9. cosmetic body shaving
  10. congregated facilities
  11. sharing equipment that is not cleaned or laundered between users
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12
Q

Clindamycin:
dosage
comments

A

600 mg/kg IV q8h
300-450 mg PO TID

  • excellent tissue & abscess penetration
  • risk for C. difficile
  • inducible resistance in MRSA
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13
Q

Trimethoprim-Sumfamethoxazole (TMP/SMX):
dosage
comments

A

1 or 2 double-strength tablets PO BID

unreliable for S. pyogenes (will need to combine w/amoxicillin to cover for group A strep)

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14
Q

Doxycycline:
dosage
comments

A

100 mg PO BID

unreliable for S. pyogenes (will need to combine w/amoxicillin to cover for group A strep)

DO NOT USE in KIDS <8 yo

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15
Q

Linezolid:
dosage
comments

A

600 mg IV q12h
600 mg PO BID

expensive
no cross-resistance w/other abx classes

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16
Q

Vancomycin:
dosage
comments

A

1 g IV q12h

parenteral DOC for tx of infections caused by MRSA

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17
Q 
Erysipelas:
def
main pathogen
distribution
presentation
A

superficial cellulitis w/marker dermal lymphatic involvement (causing edematous or raised skin)

group A strep=main pathogen

(U) affects lower extremities & the face

pain, superficial erythema, plaque-like edema w/a sharply defined margin to normal tissue

plaques may develop overlying blisters (bullae)

may be a/w high white count

may be preceded by chills, fever, HA, V, joint pain

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18
Q

erysipelas: example presentation

A

large, shiny erythematous plaque w/sharply demarcated borders located on the leg

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19
Q

uncomplicated erysipelas: most appropriate tx

A

oral abx

immediate empiric abx therapy should be started (cover most common pathogen-Streptococcus)

monitor pts closely & revise therapy if there is poor response to initial tx

elevation of the involved area

tx tinea pedis if present

20
Q

Skin Abscess:
description
&
presentation

A

collection of pus within the dermis & deeper skin tissues

painful, tender, fluctuant & erythematous nodules

often surmounted by a pustule & surrounded by a rim of erythematous edema

spontaneous drainage of purulent material may occur

21
Q

Skin abscess: next best management

A

REQUIRE incision & drainage (TOC)
and
offer HIV test (to pts w/risk factors, such as IVDU)

22
Q

When are abx recommended for abscesses? (8)

A

when a/w:

  1. severe or extensive dz
  2. rapid progression in presence of associated cellulitis
  3. signs & sxs of systemic illness
  4. associated comorbidities or immunosuppression
  5. extremes of age
  6. abscess in difficult to drain area (e.g. face, hand or genitalia)
  7. associated septic phlebitis
  8. lack of response to I&D alone
23
Q

abscesses REQUIRE

A

INCISION & DRAINAGE
-most experts recommend irrigation, breaking or loculations & packing following I & D

-WOUND CULTURES should always be sent

24
Q

recommend abx in pts with

A

multiple lesions, extensive surrounding cellulitis, immunosuppression, risk for MRSA or systemic signs of infection

25
Q

Furuculosis

A

a furuncle (boil) is an acute, round, tender, circumscribed, perifolliculur abscess that generally ends in central suppuration

26
Q

Carbunculosis

A

a carbuncle is a coalescence of several inflamed follicles into a single inflammatory mass with purulent drainage from follicles

27
Q

furuncles & carbuncles are what?
occur where?
(U) cause

A

furuncles & carbuncles are a subtype of abscesses

  • preferentially occur in skin areas containing hair follicles exposed to friction & perspiration
  • common areas include the back of the neck, face, axillae & buttocks

(U) caused by Staphylococcus aureus

pts commonly tx w/oral abx

28
Q

tx of solitary small furuncle

A

warm compress to promote drainage may be sufficient

29
Q

tx of larger furuncles & carbuncles

A

manage as you would an abscess

30
Q

Folliculitis:
what is it?
how does it present?

A

a superficial bacterial infection of the hair follicles

presents as small, raised, erythematous, occasionally pruritic pustules <5mm diameter

genital folliculitis may be sexually transmitted

31
Q

Folliculitis: pathogens

A

majority are due to Staphylococcus aureus

if hot tub/swimming pool exposure, consider pseudomonas folliculitis

pustules a/w marked erythema and scaling may represent genital candidiasis

32
Q

Folliculitis: management (4)

A
  1. thoroughly cleanse the affected area w/antibacterial soap & water 3x/day
  2. superficial pustules will rupture & drain spontaneously
  3. oral or topical anti-staphylococcal agents may be used
  4. deep lesions of folliculitis represent small follicular abscesses & should be drained
33
Q

Impetigo:
what is it
who is it seen in

A

common superficial bacterial skin infection

contagious, easily spread among ppl in close contact

most (C) seen in kids aged 2-5, but older kids & adults can be affected

34
Q

Impetigo: organisms

A

most are due to S. aureus

remainder due to S. pyogenes or a combo of these two

35
Q

name the 3 clinical variants of impetigo

A

non-bullous impetigo
bullous impetigo
ecthyma

36
Q

Non-bullous impetigo presentation

A

aka impetigo contagiosum

lesions begin as papules surrounded by erythema; progress to form pustules that enlarge & break down to form thick, adherent crusts with a characteristic golden appearance

37
Q

Bullous impetigo presentation

A

seen in young children

flaccid bullae with clear yellow fluid, which later becomes purulent

ruptured bullae leave a thick brown crust

38
Q

Ecthyma

A

ulcerative form of impetigo in which the lesions extend through the epidermis & deep into the dermis

consist of “punched out” ulcers covered w/yellow crust surrounded by raised margins

39
Q

Oral abx used to tx impetigo (5)

A
  1. dicloxacillin
  2. cephalexin
  3. erythromycin (some strains of Staph aureus & Strep pyogenes may be resistant)
  4. clindamycin
  5. amoxicillin/clauvanate
40
Q

Impetigo tx (other comments)

A

dosing guidelines vary according to age

topical therapy w/mupirocin ointment may be equally effective to oral abx if the lesions are localized in an otherwise healthy pt

41
Q

Necrotizing fasciitis:
what is it
onset

A

life threatening infection of fascia just above the muscle

progresses rapidly within hours
may follow surgery or trauma, or have no preceding visible lesion

42
Q

Necrotizing fasciitis: presentation

A

expanding dusky, edematous, red plaque with blue discoloration

  • may turn purple & blister
  • anesthesia of the skin of affected area
43
Q

Necrotizing fasciitis: organism

A

group A streptococcus, Staphylococcus aureus or a variety of other organisms

44
Q

Necrotizing fasciitis: treatment

A

medical/surgical emergency with up to a 20% mortality rate

CONSULT SURGERY IMMEDIATELY

tx includes widespread debridement & broad-spectrum antibiotics

45
Q

Necrotizing fasciitis: poor prognostic factors include (5)

A
  1. delay in diagnosis
  2. age >50
  3. diabetes
  4. atherosclerosis
  5. infection involving the trunk

Q5 Dermatology (14 decks)

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