What Alexander Fleming did to made to improve health or treat?

Alexander Fleming is best known for his discovery of penicillin in 1928, which marked the beginning of modern antibiotics. His observation that the mold Penicillium notatum produced a substance that killed bacteria led to the development of penicillin as a treatment for bacterial infections. This breakthrough significantly improved health outcomes, reducing mortality rates from infections and paving the way for further advancements in antimicrobial therapies. Penicillin has since saved countless lives and remains a cornerstone of modern medicine.