Who was the research scholar in Fleming's first clinical trial of penicillin?

Stuart Craddock was the research scholar involved in Fleming's first clinical trial of penicillin.

Craddock joined Fleming's laboratory after Fleming's 1928 observation of mold inhibiting bacterial growth. Together with Frederick Ridley, he investigated the properties of the crude “mold juice” and attempted to obtain a more useful preparation. Craddock later developed a severe infection of the nasal antrum, or sinus, giving Fleming an opportunity to try the material clinically.

Beginning on 9 January 1929, Fleming applied or injected crude penicillin into the infected area, but the treatment failed. The likely reason was that the infection involved Haemophilus influenzae, then called Pfeiffer's bacillus, which Fleming had found was not susceptible to penicillin. This unsuccessful attempt should not be confused with the first successful therapeutic use: Cecil George Paine treated eye infections successfully in Sheffield in 1930.

Arthur Dickson Wright also received samples for possible testing, but records do not clearly document a specific treatment. Craddock is therefore the canonical answer for Fleming's first clinical trial.