Believed that germs caused death and founded aseptic surgery.

Joseph Lister (1827-1912) founded aseptic surgery by applying Louis Pasteur's germ theory, introducing carbolic acid as a surgical disinfectant to prevent post-operative infections. His techniques dramatically reduced surgical mortality rates and transformed modern surgery.

Robert Koch identified specific microorganisms that cause diseases such as tuberculosis, but he did not develop or found aseptic surgical techniques.

Alexander Fleming discovered the antibiotic properties of penicillin in 1928, which was a breakthrough in treating infections after they occur - not in preventing surgical contamination.