MRCP2-3411

A 35-year-old man presents with increasing muscle weakness. He visited his primary care physician (PCP) 5 days ago, reporting difficulty standing up from a seated position. His family has brought him to the Emergency Department as he is having trouble swallowing and can only produce garbled speech.
During the examination, there is a noticeable overall weakness with absent reflexes on both sides. Upon further inquiry, he mentions having experienced food poisoning approximately four weeks ago. Electrophysiological tests reveal indications of conduction block at various locations.
What is the most probable diagnosis?