Which former research student examined Fleming's culture plates with him in September 1928?

Daniel Merlin Pryce examined Fleming’s culture plates with him in September 1928. Pryce was a former research student who had worked with Fleming on variations in Staphylococcus aureus colonies.

Fleming returned to St Mary’s Hospital in London on 3 September after his summer break. Together, he and Pryce noticed an open culture plate contaminated by blue-green Penicillium mould. The staphylococci around the mould had been destroyed, while colonies farther away remained intact.

Pryce is sometimes confused with Stuart Craddock or Frederick Ridley, both of whom also worked with Fleming during the early penicillin research. Craddock was Fleming’s current research scholar when Fleming left for his holiday, while Ridley later investigated the mould’s chemical properties. Pryce’s role belongs specifically to the first examination of the remarkable contaminated plate.

The observation led Fleming to test the mould in fresh cultures and identify an antibacterial substance, which he named penicillin in 1929. The discovery itself was Fleming’s, but the first discussion of the plate involved Pryce.