A 28-year-old patient complains of a pustular rash on the skin of both his shoulders, fever of 38.5°C, and feeling unwell. According to the patient's medical history, the disease onset was three days ago, after he received skin abrasions from wearing a knapsack. Objectively, the skin in the area of both his forearms is hyperemic and edematous. There are multiple small foci of superficial pustular papular rash elements. Bacteriological testing of the contents of the papules detects Staphylococcus aureus. What is the most likely diagnosis in this case?