PLE-3453

A 25-year-old man suffered major injuries to his right leg after a motorcycle accident. He was brought to the ER after 2 days due to a high-grade fever. On examination, he was febrile at 39.6°C and tachycardic at 128 bpm. His right leg is swollen and tense, with thin, dark serous fluid draining from the wound. The skin is cool, pale, and shining. Crepitus can also be felt. What is the most likely causative agent?