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A 36-year-old man presents to the emergency department for evaluation of a rash on the right forearm. The patient was recently admitted to the hospital for pain-control in the setting of nephrolithiasis. He recalls, “After I left, I was feeling fine, then the next day my arm started hurting, and I noticed a red rash near the site where I had my IV.” He is otherwise healthy and does not take any medications daily. Temperature is 38.0°C (100.4°F), pulse is 110/min, respirations are 14/min, and blood pressure is 119/77 mmHg. Physical examination demonstrates a well demarcated erythematous, warm, and painful rash over the anterior aspect of the right forearm without fluctuance. Infection with which of the following organisms is most likely responsible for this patient’s cutaneous findings?

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Cellulitis p. 491

Pasteurella multocida p. , 147

Streptococcus pyogenes p. , 134

Herpes simplex virus (HSV-1/HSV-2)

skin infections p. 491

Skin infections p. 491

Staphylococcus aureus p. , 133

skin infections p. 491

Staphylococcus pyogenes

skin infections p. 491

Streptococcus pyogenes (Group A strep) p. 134

skin infections p. 491

Viral skin infections p. 491


Cellulitis is a localized infection and inflammation of the skin and subcutaneous tissue. It most commonly affects the lower extremities, particularly the legs. Cellulitis is usually caused by Streptococcus pyogenes or Staphylococcus aureus. If left untreated, it can lead to sepsis.


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