MSFinals-1451

A 65-year-old man (with known metastatic pancreatic cancer) presented with severe obstructive jaundice and signs of hepatic encephalopathy. He was treated with a biliary stent (percutaneous transhepatic cholangiography (PTC)) and discharged when his jaundice, confusion and pruritus had started to improve. He re-presented shortly after discharge with rigors, pyrexia and feeling generally unwell. His blood cultures showed Gram-negative rods.
What is the most likely cause of his current presentation?