Original: Marshall is well-known for proving that the bacterium Helicobacter pylori is the cause of most peptic ulcers , reversing decades of medical doctrine which held that ulcers were caused by stress , spicy foods , and too much acid .
Simplified: After this work at Fremantle Hospital , Marshall did research at Royal Perth Hospital ( 1985-86 ) and at the University of Virginia , USA ( 1986-1996 ) , before going back to Australia .