Review Question - QID 213845

A 28-year-old homeless man presents to the emergency department with pain and discoloration of his left foot. He says that a few days ago, he accidentally stepped on a piece of scrap metal while walking across a parking lot with bare feet. He went to the emergency room and received a dose of tetanus toxoid vaccination for wound prophylaxis. Last night, he felt the sudden onset of pain on the bottom of his left foot and notes that severe pain has spread diffusely to the dorsum of his foot as well. His temperature is 100.8°F (38.2°C), pulse is 110/min, respirations are 18/min, and blood pressure is 108/58 mmHg. On physical examination, the patient’s left foot exhibits findings seen in Figure A. Palpation of the skin on the dorsum of his left foot reveals tenderness and crepitus. Which of the following organisms is most likely responsible for this patient’s current symptoms?