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DERM > Bacterial Infections of the Skin I > Flashcards

Bacterial Infections of the Skin I Flashcards

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1
Q

what is the most common bacterial infection in children?

A

staph aureus

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2
Q
  • s. aurues
    • characteristics (gram stain, shape, ect)
    • susceptible populations
    • best defense against
    • means of spread
    • other
A
  • gram +, catalase +, cocci in clusters
  • susceptible populations - HIV infected
  • best defense - intact skin
  • spread amongst healthcare workers in hospitals major cause of spread
  • m/c childhood infection
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3
Q

MRSA infection

  • mechanism
  • susceptible populations
  • ttreatment
A
  • s. aureus becomes methicillin resistant via mecA gene, which encodes an alternative penicillin binding protein: PBP-2a
  • susceptible populations:
    • ​previous Abx use*
    • recent hospitalization / chornic illness*
    • older
  • treatment: MRSA-covering Abx + mucopiricin ointment (bactroban)
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4
Q

which patients should always be treated with mupirocin ointment 2% (bactroban)

A

patients who are

  • colonized with MRSA
  • have localized impetigo
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5
Q

impetigo contagiosa:

  • pathogenesis
  • demographics
  • presentation
  • diagnosis
  • treatment
  • prognosis / complications
A
  • pathogenesis: s. aureus > s. pyogenes -> superfiical skin infection
  • demographics: m/c in children
  • presentation: on face - perioral & perinasal- occurs in phases:
    1. 2 mm erythematous papule
    2. vesicles + bullae
    3. yellow, friable (honey-colored) crust from vesicle discharge
  • dx: n/a
  • treatment:
    • localized: class IV steroid - topical mupirocin (bactroban)
      • ​if recurrent: topical mupirocin BID to nares
    • widespread: beta-lactamase resistant PCN
    • complicated: IV ceftiaxone
  • prognosis / complications: :
    • prognosis: self resolves in 2 weeks
    • complication: post-streptococcal glomerulonephritis (no risk reduction with tx)
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6
Q

how to tx recurrent impetigo contagiosa?

A
  • topical mupirocin BID to nares for 7-10 days
  • +/- chlorohexidine washes
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7
Q

bullous impetigo

  • pathogenesis
  • demographics
  • presentation
  • diagnosis
  • treatment
  • prognosis / complications
A
  • pathogenesis: s. aureus (group phage 2 type 71)
  • demographics:
    • newborns m/c
    • adults - may be indicative of HIV
  • presentation:
    • bullae (vesicle > 1cm) that is either on the
      • ​on face, hands: in kids
      • in axilla, groin: adults
      • if large & fragile - suggests pemphigous
  • diagnosis: + culture from lesions
  • treatment: n/a
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8
Q

bullous impetio in adults

  • in common in what situations?
  • may be indicative of what etiology?
A
  • warm climates
  • HIV
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9
Q

what characteristics of a bullae indicative of pemphigous vulgaris

A
  • large
  • fragile
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10
Q

staphyloccocal scalded skin syndrome (SSSS)

  • pathogenesis
  • demographics
  • presentation
  • diagnosis
  • treatment
  • complications
A
  • pathogenesis: s. aureus (group 2 phage 71) releases exofoliative toxin which is located at a mucosal surface (i.e. not isolated in lesions) & disrupts granular layer
  • demographics:
    • neonates & children m/c
    • adults - with renal failure
  • presentation:
    • FEVER + rapid desquamation of skin
    • also:
      • skin tenderness: of neck + groin + axilla in early phases
      • + nikolsky’s sign: sloughing of upper layers of skin up contact
      • blistering beneath granular layer
      • rhinorrhea / conjunctivits
  • diagnosis: take culture from mucosal surface (intact bullae will be -)
  • treatment: oxacillin/nafcillin + HYDRATION
  • prognosis / complications:
    • prognosis: poor in adults with renal disease, good in children
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11
Q

how is the diagnosis for SSSS (staphylococcal scalded skin syndrome) made & why is this important?

A
  • must be taken from mucosal surface, b/c this is where the exofoliative toxin from s. aureus is found. cultures from intact bullae will be negative
    • ​conjunctivae
    • nasopharynx
    • feces
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12
Q

compare & contrast the diagnosis of bullous impetigo vs SSSS

A
  • both: involve obtaining a culture
    • bullous impetigo: culture from lesion
    • SSSS: culture from mucosal surface - nasopharynx, conjunctiva, feces
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13
Q

what is the treatment of SSSS?

A
  • penicillinase resistant Abx + FLUID/ELECTROLYTIC REPLACEMENT
    • Abx = nafcillin, oxacillin
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14
Q

compare & contrast TEN & SSSS based on

  • cause
  • demographics
  • histology
  • involvement of mucous membranes
  • presence of nikolsky’s sign
  • treatment
A
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15
Q

toxic shock syndrome (TSS)

  • pathogenesis
  • demographics
  • presentation
  • diagnosis
  • treatment
  • complications
A
  • pathogenesis: s. aureus exotoxin (> s. pyogenes) releases TSST-1 exotoxin, a pyrogenic toxin, leading to high fever + multisystemic disease (renal m/c)
  • demographics: young, healthy adults (menstraul or not)
  • presentation (see dx)
  • diagnosis: 3 of the following criteria must be met
    • fever: of at least 102 F
    • hypoTN: SBP < 90 or < 5th percentil in children
    • rash: diffuse macular erythroderma (staph) or scarlitinform (strep)
    • desqamation of soles & palms
    • involvement of 3 + organ systems (renal m/c)
  • treatment: clindamycin + / IV FLUIDS (hypoTN +/- removal of any foreign object
  • prognosis / complications:
    • rapidly progressive / necrotizing fascitis if s. pyogenes (group B strep) cause
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16
Q

what is the treatment of TSS

A

clindamycin +/- IV fluids (hypoTN) +/- removal of any foreign object

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17
Q

compare & contrast the presentation of TSS in menstrual vs non-menstrual patients

A
  • both:
    • febrile ( > 102 F)
    • hypotensive ( SBP < 90 / < 5th percentile)
    • rash + systemic sx
  • menstrual TSS:
    • less common
    • m/c d/t superabsorbent tampons
    • prognosis better:
  • non-menstrual TSS:
    • more common
    • m/c d/t nasal packing, surgery, infections
    • prognosis worse
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18
Q

pyogenic paronychia

  • pathogenesis
  • presentation
  • treatment
A
  • pathogenesis: host of etiological agents -> inflammation of skin folds around fingernail
  • presentation: separation of epioncyium from the nail plate
  • treatment:
    • acute infection:: 1. PCN / 1st gen ceph then 2. TMP-SMX if inneffective
    • chronic infection: requires antifungal + topical steroid
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19
Q

eryrthrasma

  • pathogenesis
  • demographics
  • presentation
  • diagnosis
  • treatment
  • complications
A
  • cornyebacterium minutissimum infects interrigionous areas
  • demographics:
    • in warm, humid climate
    • IC - obesity, DM, advanced age
  • presentation: well defined pink-red patches that -> fade to brown on the that affect the interrigionous areas: axilla + groin +toe webs (esp 4th)
  • diagnosis: wood lamp will produce coral-red color
  • treatment: 20% AlCl + topical clindamycin / erythromycin
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20
Q

pitted keratolysis

  • pathogenesis
  • demographics
  • presentation
  • diagnosis
  • treatment
A
  • pathogenesis: kryptococcus sedentarius digests keratin in stratum corneum of plantar/palmar skin
  • demographics: men with sweaty feet
  • presentation: small crateriform pits (keratin plugs) on weight-bearing plantar skin + FOUL ODOR***
  • diagnosis: woods lamp will show - no flourescence
  • treatment: AlCl / botulinum toxin (tx hyperhydrosis) + Abx
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21
Q

trichomycosis axillaris

  • pathogenesis
  • presentation
  • treatment
A
  • pathogenesis : cornyeobacteria causes a superficial infection of hair follicles
  • presentation: adherent nodules (yellow, red black) on hair shaft in armpits, &:
    • characteristic odor
    • +/- colored sweat
  • treatment: antibacterial soap
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22
Q

which skin infection (s) can cornyebacteria cause and what do they look like?

A
  • erythrasma: pink-red well defined patches -> fade to brown on groin + 4th toe web
  • trichomycosis axillaris: nodules on hair follicles im armpit + odor +/- colored sweat
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23
Q

folliculitis

  • pathogenesis
  • demographics
  • presentation
A
  • pathogenesis: bacterial infection (staph m/c, psueodmonas in pools / hot-tubs) causes infection of hair follicle
  • presentation: pustules (vesicle containing white/yellow fluid content)
  • treatment:
    • general: anti-bacterial soap TID
    • chronic folliculitis of buttocks: AlCl (Drysol) qhs
    • chronic d/t s. arueus: mupirocin 2%
    • blepharitis: opthalmic ointments
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24
Q

tx of chronic folliculitis of the buttocks?

A

Drysol (aluminum chrloride) qhs

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25
Q

treatment of chronic folliculitis d/t staph arueus?

A

mupirocin

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26
Q

sycosis vulgaris

  • pathogenesis
  • presentation
A
  • pathogenesis: s. aureus causes infection of bearded region
  • presentation: pustules errupt after shaving, leaving crop of pustules behind - common seen on upper lip near nose
27
Q

define:

  • abcess
  • furuncle
  • carbuncle
A
  • abscess: localized collection of pus at any site
  • furuncle: abcess of hair follicles + surrounding tissue (only in hair-bearing areas)
  • carbuncle: collection of furnicles that can extend into subq tissue +/- systemic sx
28
Q

furunculosis

  • pathogenesis
  • demographics
  • presentation
  • treatment
A
  • pathogenesis: s. arueus infects hair follicle
  • demographics:
    • alcoholism
    • IC - diabetes, malnutrition, immune disorders
  • presentation: furcunle (acute, inflammatory abcess)
  • treatment:
    • general: warm compress + systemic Abx
    • if localized: incision & drainage then pack with idoform
      • NO I&D if nasal furuncle: Abx only
    • if chronic: mucopirocin BID to nairs + lifestyle to break cycle: chlorhexidine wash, daily laundering of bedding & clothing, frequent hand washing
29
Q

which type of localized furcuncle should NOT be incised & drained?

how should it be treated instead?

A

nasal furuncles. can be treated with Abx ONLY

30
Q

ecthyma

  • pathogenesis
  • demographics
  • presentation
  • diagnosis
  • treatment
A
  • pathogenesis: s. pyogenes,following scratching of bug bites-> ulcerative pyoderma
  • demographics: children
  • presentation: punched-out ulcers (from vesicopustules) with a purulent base
  • diagnosis: wound culture confirmatory
  • treatment: dicloxacillin or cephalexin
31
Q

scarlett fever

  • pathogenesis
  • demographics
  • presentation
  • treatment
  • complications
A
  • pathogenesis: s. aureus / s. pyogenes produces exotoxin
  • demographics: young children
  • presentation:
    • macular erythroderma or sandpaper (punctate, confluent pustule) rash
    • circumoral pallor
    • pastias lines: petichias in skin creases
    • palmoplantar desquamation
    • white or red strawberry tongue
  • treatment: a penicillin (amoxicillin)
  • complications:
    • ​glomerulonephritis
    • rheumatic fever
32
Q

erysipelas

  • pathogenesis
  • demographics
  • presentation
  • diagnosis
A
  • pathogenesis: s. pyogenes (group A strep) cause a superficial variant of cellulitis
  • demographics: pts with lymphadema & venous insufficiency have increased risk
  • presentation:
    • on legs > face:
      • painful, hot, burning patch of skin
      • sharply defined ridge-like borders advance
        • very sick: fever / chills / HA (lymphocytes > 20,000)
  • diagnosis: elevated DNase B and ASO titers
33
Q

necrotizing fascitis

  • pathogenesis
  • demographics
  • presentation
  • diagnosis
  • treatment
A
  • pathogenesis: s. pyogenes (children) / polymicrobial (adults) -> rapid progressive necrosis of subQ fat / fascia
  • demographics: IC, following surgery
  • presentation: occurs in phases:
    • severely painful erythematous induration - “pain out of proportion to skin changes”
    • RAPID decline over next 1-2 days
    • induration goes from erythematous to
      • ​dusky purple/gray
      • +/- hemorraghic
      • FOUL SMELL
    • late: skin anesthetic (no pain d/t destroyed nerves)
  • diagnosis: MRI or probe test (lack of bleeding/resistance = ominous sign)
  • treatment: extensive surgical debridement = MAINSTAY, +
    • emperic IV therapy with broad spectrum coverage
34
Q

blistering distal dactylitis

  • pathogenesis
  • demographics
  • presentation
  • treatment
A
  • pathogenesis: s. pyogenes
  • demographics: 2-16 OR DM
  • presentation: tense blister on volar pat pad of digit phalanx
  • treatment: PCN + I&D
35
Q

perineal dermatitis

  • pathogenesis
  • demographics
  • presentation
  • treatment
  • complications
A
  • pathogenesis:s. pyro > staph
  • demographics: 1- 8 years old
  • presentation: sharp red plaques that
    • ​surround perianal region
    • are: PAINFUL - esp on defection, often leading to fecal retention by patient
  • treatment: oral cefuroxime or penicillin
  • complications: ppp
    • post-strep glomerulonephritis
    • psoriasis gluttate outbreak
36
Q

erythema marginatum

  • pathogenesis
  • demographics
  • presentation
A
  • pathogenesis: streptoccocal infection in the setting of ARF
  • demographics: 5-15 years
  • presentation: lesions that are ANNULAR + MIGRATORY + EXPANDING
    • ​can migrate “12mm in 12 hrs”
37
Q

erysipeloid of rosenbach

  • pathogenesis
  • demographics
  • presentation
  • complications
A
  • pathogenesis: erysipelothrix rhusiopathiae (rod shaped, gram +) contracted via an abrasin to the hand
  • demographics: fisherman / fish handlers / poulty handlers
  • presentation: purplish swelling of hands that is migratory
  • complications: endocarditis (rare)
38
Q

what are the 4 signs of inflammation?

A
  • rubor (erythema)
  • calor (warmth)
  • dolor (pain)
  • tumor (swelling)
39
Q

cutaneous anthrax

  • pathogenesis
  • demographics
  • presentation
  • diagnosis
  • treatment
A
  • pathogenesis: bacilllus anthracis (gram +, spore forming rod)
  • demographics:
    • occupational - contact with animals
    • bioterrorism
  • presentation: bullae erupt to form eschar (central necrosis) that is
    • NON-TENDER
    • tender regional lypmh nodes -> suppurative adenitis
  • diagnosis: gamma bacteriophage
  • treatment: PCN G 2 million units IV q 6 hrs for 4-6 days
40
Q
A

oslers node (s. aureus)

nodule with white center, PAINFUL (osler = ouch)

41
Q
A

janeway lesions (s. aureus)

small, hemorrhagic lesions on palms/soles - PAINLESS

42
Q
A

impetigo contagiosa

ruptured vesicles -> yellow, friable (honey colored) crust (s. aureus > s. pyogenes)

43
Q
A

impetigo contagiosa

ruptured vesicles -> yellow, friable (honey colored) crust (s. aureus > s. pyogenes)

44
Q

impetigo contagiosa

ruptured vesicles -> yellow, friable (honey colored) crust (s. aureus > s. pyogenes)

A
45
Q
A

bullous impetigo

46
Q
A

SSSS - desquamation, seen in newborns

47
Q
A

SSSS

rhinorrhea

48
Q
A

SSSS-histology

subcorneal blister (in stratum granulum) with inflammatory infiltrate

49
Q
A

staphyloccocal toxic shock syndrome (TSS)

desquamation of the palms & soles

50
Q
A

pyorgenic paronychia

separation of eponychium from the nail plate

51
Q
A

erythrasma (coryneobacterium)

pink-red -> brown lesions in the axilla, groin, 4th toe web

52
Q
A

erythrasma (corynebacterium)

wood lamp: produces coral red color

53
Q
A

pitted kartolysis (kytococcus sedentarius)

small, crateriform pits (keratin plugs) + foul odor

54
Q
A

trichomycosis axillaris (corynebacterium)

adhered yellow + red + black nodules on hair shafts in axilla

55
Q
A

folliculitis: cysts containing wet/yellow fluid

56
Q
A

sycosis vulgaris (s. aureus)

ruptured pustules following shaving that in beared region including upper lip near nose

57
Q
A

chronic furunculosis

acute, inflammatory abscess of hair follicles

58
Q
A

ecthyma (s. pyogenes > s. aureus)

ulcerative pyoderma on the shins & dorsal feet following scratching of bug bites

59
Q
A

erysipelas (s. pyogenes)

cellulitis patch that is painful + hot to touch + may burn; has a distinctive advancing edge

60
Q
A

necortizing fascitis (s. pyogenes or polymicrobial)

lesions that is: erthyematous w/ disproportional pain then -> rapidly progresses -> dusky purple/gray + foul smelling then -> anesthetic (numb)

61
Q
A

blistering distal dactylitis (s. pyogenes)

tense, superficial blister on volar pad phalanx of digit

62
Q
A

perineal dermatitis

superficial, perineal plaques up to 3 cm from anus -> PAINFUL: esp on defication

63
Q
A

erysipeloid of rosenbach

purplish swelling of hands - common in fisherman / fish handlers

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