MC used his cheat to cure tuberculosis, and at the same time provide a primitive microscope to other apothecaries so they can observe the cause and start acknowledging the roles of micro-organisms in illnesses and medical research.
He used his ability to create anti-biotic because the Black Plague was upon them
right now, but he told his father how to make it, and subsequently a fungus-researcher was commissioned to create anti-biotic for future use.
He repeatedly stated that he wanted his knowledge can be used after he passed away. I’m not sure how one can read the novel and assume he’ll just let the knowledge be lost after his generation.