FCEM2-1273

A 35-year-old man comes to the clinic complaining of increasing numbness and weakness in his legs over the past 4 days. The symptoms seem to be spreading upwards towards his thighs, and he has also noticed some weakness in his hands. He mentions that he had a bad bout of diarrhea about three weeks ago, but otherwise, he has been healthy. What is the most likely organism responsible for his symptoms?