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Milton Wainwright (Letters, THES, November 22) criticises my feature (THES, November 15) for questioning Sir Alexander Fleming's contribution to the development of antibiotics.

Neither I nor other scholars have denied that Fleming recognised the antibiotic properties of penicillin, or that he used penicillin therapeutically in 1928 and 1929 and employed it as a laboratory reagent in the 1930s.

But by 1930, Fleming's early optimism had gone. Thereafter, he mentioned penicillin primarily as a laboratory reagent for isolating specific bacteria. He gave little help to biochemists researching the properties of penicillin. Most important, he never tested penicillin on an animal injected with lethal bacteria.

None of this is to the discredit of Fleming. Impure penicillin loses its potency very quickly, and so after a series of disappointing trials he sensibly moved on to studying other substances.

John Waller
Wellcome Trust Centre for the History of Medicine
University College London