Infectious Disease Flashcards by Gillian Collom

Cellulitis

GAS and S. aureus = adults
HIB = in children <3 yo
4 factors:
- 1. erythema/hyperpigmentation
- 1. warmth
- 1. Edema
- 1. pain
Diagnosis in immunocompromised host:
- skin cx
- aspirate/blood cx
- mild leukocytosis with left shift and a mild increased sed rate
tx: empiric
- cephalexin (keflex)
- non-betalactam
  - clindamycin
  - tetracycline
- elevate lower legs
- cold compresses for pain
- send to hospital if at risk for systemic disease

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Erysipelas

**STREAKING**, does not involve the deeper layer (subcutaneous tissue)
caused by GAS and s.aureus in adults, HIB in children <3 yo
4 factors:
- 1.erythema
- 2.warm
- 1. pain
- 4.edema
Diagnosis:
- in immunocompromised host:
  - skin cx, aspirate/blood cx
- Mild leukocytosis with a left shift, and a mild increased sed rate
tx: treat empirically
- cephalexin (keflex)
- non-beta-lactams
  - clindamycin or tetracycline
- elevate legs and cold compresses
- send to hospital if at risk for systemic infection

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Impetigo

**caused by Staph**
erythema and Honey crusted
diagnosis:
- gram stain and cx
tx:
- acute: mupirocin ointment 2-3x/day for 10-14 days
- oral abx:
  - cephalexin if concern for MRSA: doxycyline, clindamycin or BActrim

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bullous impetigo

Caused by S.aureus
favor trunk, can have fever and diarrhea
tx: mupirocen 2-3x/day for 10-14 days
- oral:
  - cephalexin
  - if concern for MRSA: doxycyline, clindamycin, or bactrim
- RECURRENT:
  - mupirocen BID for 2-3 weeks
    - wash the area with CLN cleansers or dilute bleach baths ( 1/2 cup in a full bath)

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Furuncle/Abscess

furuncle involves hair follicle, abscess does not
**causative agent: S. aureus**
firm, fluctuant mass, painful to touch
exudes from the surface, with purulent material
diagnosis:
- clinical, can cx if needed
tx: I&D with warm moist compresses as well

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Pitted keratolysis

**caused by corynebacterium minutissimum (gram positive bacilli) **
tends to erupt on weight bearing surfaces and common in pts with hyperhidrosis
diagnosis:
- clinical
tx:
- promote dryness
- topical clindamycin or erythromycin (BID)
- wash feet with BPO wash

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Erythrasma

**causative agent is Corynebacterium minutissimum** (gram positive bacilli)
reddish, brown patch that is uniformly scaly
non-inflammatory border and no advancing border
not very pruritic
Diagnosis:
- Wood’s lamp: coral-red fluorescence
- want to do KOH to r/o fungal
tx:
- decrease moisture
- topical clindamycin or erythromycin

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Candidiasis

satellite pustules
**affects the scrotum**
erythematous patch
**causative agent candida albicans**
Diagnosis:
- KOH wet prep
Tx:
- ketoconazole 2% cream, fluconazole daily for 2-4 weeks
- Mucosal:
  - clotrimazole trouch 5x/day
  - Nystatin swish and swallow
  - oral fluconazole

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Tinea Corporis

**causative agent: Trichophyton rubrum and Trichophyton mentagrophytes**
Annular, scaly borders, advancing, erythematous
Diagnosis:
- KOH wet prep
- Fungal Cx
tx:
- Ketoconazole 2% cream (imidazoles) or Terbinafine 1% cream (allyamine)
- oral:
  - fluconazole
  - terbinafine (for tinea unguium 250 mg QID for 6-12 weeks vs once weekly for 52 weeks)

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Tinea Incognito

**causative agent: Trichophyton rubrum and Trichophyton mentagrophytes**
Annular, scaly borders, advancing, erythematous
Diagnosis:
- KOH wet prep
- Fungal Cx
tx:
- Ketoconazole 2% cream (imidazoles) or Terbinafine 1% cream (allyamine)
- oral:
- fluconazole
- terbinafine (for tinea unguium 250 mg QID for 6-12 weeks vs once weekly for 52 weeks)

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Tinea Cruris

**causative agent: Trichophyton rubrum and Trichophyton mentagrophytes**
Annular, scaly borders, advancing, erythematous, does not affect the scrotum
Diagnosis:
- KOH wet prep
- Fungal Cx
tx:
- Ketoconazole 2% cream (imidazoles) or Terbinafine 1% cream (allyamine)
oral:
- fluconazole
- terbinafine (for tinea unguium 250 mg QID for 6-12 weeks vs once weekly for 52 weeks)

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Tinea Manuum

**causative agent: Trichophyton rubrum and Trichophyton mentagrophytes**
Tinea manum: “one hand, two feed syndrome”
Diagnosis:
- KOH wet prep
- Fungal Cx
tx:
- Ketoconazole 2% cream (imidazoles) or Terbinafine 1% cream (allyamine)
oral:
- fluconazole
- terbinafine (for tinea unguium 250 mg QID for 6-12 weeks vs once weekly for 52 weeks)

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Tinea Pedis

interdigital, moccasin,inflammatory (vesicular)
**causative agent: Trichophyton rubrum and Trichophyton mentagrophytes**
Diagnosis:
- KOH wet prep
- Fungal Cx
tx:
- Ketoconazole 2% cream (imidazoles) or Terbinafine 1% cream (allyamine)
oral:
- fluconazole
- terbinafine (for tinea unguium 250 mg QID for 6-12 weeks vs once weekly for 52 weeks)

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Tinea Faciei

unilateral erythematous face rash

**causative agent: Trichophyton rubrum and Trichophyton mentagrophytes**

Diagnosis:
- KOH wet prep
- Fungal Cx
tx:
- Ketoconazole 2% cream (imidazoles) or Terbinafine 1% cream (allyamine)
oral:
- fluconazole
- terbinafine (for tinea unguium 250 mg QID for 6-12 weeks vs once weekly for 52 weeks)

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Tinea Capitis

**causative agent: Trichophyton rubrum and Trichophyton mentagrophytes**

Tinea capitis: requires oral tx with griseofulvin plus topical medicated shampoo (ketoconazole 2% shampoo)
Diagnosis:
- KOH wet prep
- Fungal Cx
tx:
- Ketoconazole 2% cream (imidazoles) or Terbinafine 1% cream (allyamine)
oral:
- fluconazole
- terbinafine (for tinea unguium 250 mg QID for 6-12 weeks vs once weekly for 52 weeks)

Tinea Versicolor

**caused by Malassezia furfur**
risk factors: high temps and humidity
Multiple brown, tan, or pink oval to round macules/patches or thin plques with subtle scales
common in upper trunk/shoulders
can be hyper/hypopigmented
diagnosis:
- KOH wet prep
- Wood’s Lamp: ywllo-green fluorescensce
- DDx post-inflammatory hypo/hyperpigmentation
tx: ketoconazole 2% shampoo
- OTC selenium sulfide or zinc shampoos
pt ed:
- may take months for pigment to return
- this is a chronic condition
  - weekly maintenance therapy

Lice

caused by **Pediculus humanus capitis**
erythema, scaling, excoriations, lymphadenopathy
High yield locations: above the ears and lower occipital scalp
Diagnosis:
- clinical
Tx:
- Permethrin shampoo = first line
- Malathion = second line
- Ivermectin ⇒ DO NOT GIVE TO CHILDREN <15kg
- 7 days in bag or washed in HOT water

Scabies

caused by Sarcoptes scabiei hominis
mite lives in the stratum corneum
severe pruritus worse at night/ in shower
Diagnosis:
- delta-wingjet sign
- Biopsy: but difficult to capture the organism
- Mineral Oil Prep: very time consuming
Tx:
- Permethrin 5% applied before bed twice, separated by one week
- 10 days of storage for clothing/bedding or washed in HOT water
pt ed:
- pruritus and lesions will last 2-4 weeks after tx

Condyloma accuminatum

Causative agent: **HPV**
tiny, painless papules that evolve into soft, fleshy cauliflower-like (barnacle like) lesions
Diagnosis:
- clinical or serologies
Tx:
- 80% resolve on their own
- salicylic acid
- cryotherapy (liquid nitrogen)
- electrocauterization or surgical remove
Prevention: HPV vaccine

Herpes Simplex Virus

dsDNA virus
small round vesicle on erythematous base
PAINFUL, burning grouping of vesicles
- may become umbilicated or pustular
- then experience erosion/ulceration and crust with scalloped border
diagnosis:
- Viral cx :but sensitivity = 50%
- PCR: higher sensitivity than cx
- Tzank smear = multinucleated giant cells
tx:
- valacyclovir
- acyclovir
- protection from sun
- consider prophylaxis

Verrucae vulgaris

warts caused by HPV (dsDNA)
hyperkeratotic dome shaped papules or plaques with punctated black dots (thrombosed capillaries)
diagnosis:
- clinical
- serologies
tx: 80% will resolve on their own
salicylic acid
cryotherapy
electro cauterizatiion/surgery
prevention:
- HPV vaccine

Verrucae planae

flat warts, made worse by shaving
caused by HPV (dsDNA)
diagnosis:
- clinical
- serologies
tx: 80% will resolve on their own
- salicylic acid
- cryotherapy
- electro cauterizatiion/surgery
prevention:
- HPV vaccine

Verrucae vulgaris

plantar/palmar warts: tender to pressure
diagnosis:
- clinical
- serologies
tx: 80% will resolve on their own
- salicylic acid
- cryotherapy
- electro cauterizatiion/surgery
prevention:
- HPV vaccine

**Molluscum contagiosum** * caused by \*\***DNA poxvirus\*\*** * spread via skin2skin contact * tends to appear near skin folds, lateral trunk, thighs, buttocks, genitals and FACE * diagnosis: * clinical diagnosis * serologies * tx: * should spontanously resolve in immunocompetent patients * tx underlying eczema * encourage daily skin hydration * **cantharidin** = creates more inflammation which triggers an immune response * can do curettage (VERY PAINFUL) * cryotherapy * retinoid

**Herpes Zoster** * aka shingles * **Hutchinson's sign**: involvement of CN V₁ = urgent referral to **OPTHALMOTHOLOGIST** * diagnosis: * often clinical * viral PCR or viral cx from a **new vesicle** * tx: **acyclovir or valacyclovir ASAP** * pt ed: * may have post-herpetic neuralgias * **tx: gabapentin, tricyclic antidepressants, lidocain patches**

**Fifth's Disease** * \*\*caused by **Parvovirus B19**\*\* ssDNA aka slap cheek * **erythema infectiosum** * **Bright red, macular erythema on cheeks** 7-10 days after prodromal sxs * **lacy, reticulated pattern of erythematous macules** favors **extremities \> trunk** * diagnosis: * clinical * tx: * supportive care * complications: * **hydrops faecalis** * **arthralgias of the small joints of the hands**

**Hand, Foot and Mouth Disease** * caused by \*\***coxsackievirus A16**\*\* * ssRNA virus * **Enterovirus A71**: much more severe, can be fatal * msot common in **summer and fall** * **onychomadesis**: * fingernails/toenails fall off **1-2 months** later (especially with **coxsackie virus A16**) * diagnosis: * clinical * tx: * resolves within 1-2 weeks * complications: * **otitis media** * **pneumonia** * **encephalitis**

**Measles** * aka rubeola caused by **RNA paramyxovirus** (ssRNA) * Prodromal sxs: * **cough, coryza, conjunctivitis** * fever * **Koplik spots** * **exanthem that spreads cephalocaudally** * **Morbillaform rash** * diagnosis: * clinical * serologies * Tx: * supportive