A 12-year-old girl develops fever, abdominal pain, and bloody diarrhea 1 to 2 days after eating a hamburger at a fast food restaurant. Physical examination reveals an extensive purpuric skin rash. The patient develops oliguria, and laboratory studies show elevated serum levels of BUN and creatinine. Which of the following is the most likely etiologic agent responsible for this patient’s condition?

**Core Concept**
The patient's symptoms, including fever, abdominal pain, bloody diarrhea, purpuric skin rash, and acute kidney injury, suggest a diagnosis of a systemic infection caused by a bacterial toxin. This presentation is characteristic of a condition known as **Hemolytic-Uremic Syndrome (HUS)**, which is often associated with **Shiga toxin-producing Escherichia coli (E. coli)**.

**Why the Correct Answer is Right**
The patient's symptoms are consistent with HUS, a condition caused by Shiga toxin, which is produced by certain strains of E. coli. The toxin damages the lining of blood vessels, causing them to leak and leading to the formation of blood clots in small blood vessels. This results in the destruction of red blood cells, acute kidney injury, and the development of a purpuric rash. The patient's recent consumption of a hamburger at a fast food restaurant increases the likelihood of E. coli infection.

**Why Each Wrong Option is Incorrect**
* **Option A:** Staphylococcus aureus is a common cause of food poisoning, but it typically presents with symptoms such as vomiting and diarrhea, rather than a purpuric rash and acute kidney injury.
* **Option B:** Clostridium difficile is a cause of antibiotic-associated diarrhea and colitis, but it does not typically cause a systemic infection or a purpuric rash.
* **Option D:** Salmonella species can cause food poisoning, but they are less commonly associated with HUS and a purpuric rash.

**Clinical Pearl / High-Yield Fact**
Shiga toxin-producing E. coli is a common cause of HUS in children, and the disease often follows a diarrheal illness caused by E. coli. The patient's symptoms, including a purpuric rash and acute kidney injury, are characteristic of HUS, and a high index of suspicion should be maintained in any child presenting with these symptoms.

**Correct Answer:** C. Shiga toxin-producing Escherichia coli (E. coli)

✓ Correct Answer: B. Escherichia coli 0157-H7