PANCE Blueprint Dermatology (5%)

Bacterial Infections (PEARLS)

The NCCPA™ PANCE Dermatology Content Blueprint covers three dermatologic bacterial infections

Cellulitis (ReelDx)
ReelDx Virtual Rounds (Cellulitis)
Patient will present as → a 64-year-old female with a 4 cm × 7 cm edematous, red, hot tender area on the left thigh. The lesion has gotten larger over the past 6 hours. She tells you she has also had a low-grade fever and some chills. On physical exam, there is a poorly demarcated 12cm red and tender plaque on her right calf. Some parts resemble an orange peel. There is a superficial cut in the middle of the plaque.

An acute bacterial skin and skin structure infection of the dermis and subcutaneous tissue; characterized by pain, erythema, warmth, and swelling. Margins are flat and not well demarcated.

  • Caused by Staphylococcus and Streptococcus in adults
  • H. influenzae or strep pneumonia in children
  • Cellulitis does not have sharp, well-defined borders, unlike an erysipelas infection

DX: Culture should be taken of all purulent wounds and followed up in 48 hours

Treat mild cellulitis (MSSA)

    • Cephalexin 500 mg QID x 5-7 days
    • Cefuroxime 500 mg BID x 5-7 days
    • If PCN allergy - Clindamycin 450 mg TID x 5-7 days

Cat bites with augmentin or doxycycline if PCN allergic

    • Puncture wound with Cipro (cover pseudomonas)

Treat purulent or methicillin-resistant Staphylococcus aureus infection (MRSA) with

  • Trimethoprim-sulfamethoxazole (TMP-SMZ) 1 DS tab PO BID x 7 days
  • Clindamycin 450 mg PO TID x 7 days
  • Doxycycline 100 mg PO BID x 8 days
  • Intravenous Vancomycin or Linezolid

Cellulitis

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Erysipelas
Patient will present as → a 19-year-old female with a painful rash on her left leg. She had a small bug bite in the same area about three weeks ago. Since then, the area has become red, painful, and hot. On physical exam, you note shiny, raised, indurated, and tender plaque-like lesions on the left leg. The redness is well-demarcated and hot to the touch. You send her home on penicillin.

A distinct form of cellulitis notable for acute, well-demarcated, raised superficial bacterial skin infection with lymphatic involvement almost always caused by Streptococcus pyogenes

  • Symptoms may include redness and pain at the affected site, fevers, and chills
  • It looks like cellulitis, but it is well-demarcated and caused by group A strep (strep pyogenes)

DX: Wound culture and sensitivity

  • CBC, ↑ CRP, ↑ ESR, ↑ WBCs; antistreptolysin titer O shows streptococcal involvement
  • Blood cultures

TX: Treat with antibiotics: regimen depends on location and severity

  • Mild can be treated with Penicillin G
    • Patients with an allergy to penicillin can be treated with erythromycin or clindamycin
  • Moderate: Trimethoprim-sulfamethoxazole (TMP-SMX)-DS: 1–2 tablets PO BID and penicillin VK 500 mg PO QID or cephalexin 500 mg PO QID
  • Severe: IMP or MER or ERTA IV and linezolid 600 mg IV/PO BID or vancomycin IV or daptomycin 4 mg/kg IV q24h

Erysipelas

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Impetigo
ReelDx Virtual Rounds (Impetigo)
Patient will present as → a 5-year-old girl with crusting facial lesions present for 3 days. The mother reports that prior to the development of the facial lesions, her daughter was scratching at insect bites. Examination reveals a red facial rash with a golden “honey-colored crust” and pruritus.

Child < 6 y/o complaining of non-painful, pruritic lesions on the face

  • The main symptom is red sores that form around the nose and mouth. The sores rupture, ooze for a few days, then form a yellow-brown crust
  • honey-colored and weeping
  • Most commonly caused by S. aureus

Nonbullous impetigo: the most common form of impetigo caused by staphylococcus aureus or streptococcus pyogenes characterized by honey-colored crusts on the face and extremities

Bullous impetigostaphylococcus aureus impetigo that progresses rapidly from small to large flaccid bullae (newborns/young children) caused by epidermolytic toxin release. There is less lymphadenopathy and the trunk is more often affected; < 30% of patients

  • When the bullae rupture, yellow crusts with oozing result

DX: The diagnosis is usually made clinically, but rarely a culture may be useful

TX: topical mupirocin, dicloxacillin, cephalexin for more severe illness

  • Complications: poststreptococcal glomerulonephritis

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