Heinrich Hermann Robert Koch was a researcher from Germany who studied the causative agents of infectious diseases in various parts of Europe, Africa, and Asia during the late nineteenth and early twentieth centuries. Koch developed what researchers call Koch’s postulates, which are four criteria designed to establish whether a bacterium causes a certain disease, and as of 2025, many researchers still use Koch’s postulates to guide their research. He also received the Nobel Prize in Physiology or Medicine for his discovery of Mycobacterium tuberculosis, which is the bacterium responsible for tuberculosis, an infectious disease that primarily attacks the lungs. Koch’s research on identifying disease-causing bacteria for various infectious diseases has advanced disease prevention and treatment, especially for tuberculosis, which has the ability to transmit from mother to child.

Albert Ludwig Sigesmund Neisser was a physician and scientist working in Poland who, in 1879, identified the bacterium that causes gonorrhea. Before Neisser’s discovery, physicians and scientists were unsure of what causes gonorrhea, a sexually transmitted infection, or STI, that typically causes genital pain and discharge in those infected. Using newly available microscopy techniques, Neisser examined genital discharge from patients with gonorrhea and observed the bacteria that eventually became known as Neisseria gonorrhoeae, named in his honor. Beyond discovering the bacterial cause of gonorrhea, Neisser also directed a dermatology clinic in Breslau, Poland, and researched other diseases including syphilis and leprosy. In addition to his discoveries, he also experienced scandals and ethical controversies regarding his research practices, which resulted in the implementation of directives regarding informed consent. By identifying the causative agent of gonorrhea, Neisser enabled future physicians and scientists to develop treatments for a disease that can cause infertility and be passed from mother to child causing serious illness in infants.