In 1847, Dr. Ignaz Semmelweis recognized that ‘cadaverous particles’ could cause disease. In his report ‘The Etiology, Concept, and Prophylaxis of Childbed Fever’, Semmelweis observed the different habits between two maternity clinics. In doing so he tried to conclude why one clinic had drastically more childbed fever mortalities in comparison to the other. While studying the habits between the two clinics, he hypothesized that ‘cadaverous particles’ caused the deaths. After this discovery Semmelweis suggested that doctors should disinfect their hands with chlorine before seeing patients in order to reduce the mortality rate. Despite his hypothesis being true, the doctors did not adhere to Semmelweis’ suggestions because they felt like they were being accused of causing the mortalities.
Joseph Lister is coined the ‘father of modern surgery’. In 1867, Lister realized the surgical implications of Louis Pasteur’s studies on the fermentation of microorganisms and applied the findings to his own medical practice . He made improvements for surgical procedures by using carbolic acid, also known as phenol, to sterilize wounds. The antiseptic method that was developed reduced bacterial contamination in the wounds. As a result, a decrease in mortality rates were seen when using Lister’s antisepsis method. Much like Semmelweis, Lister’s contribution to medicine further demonstrated the need to acknowledge that a change in medical habits can prevent disease transmission.
In 1881, Koch published his method on how to isolate pure cultures of bacteria and subsequently demonstrated how the isolated colonies could cause disease. Koch was the first to scientifically prove that bacteria cause disease. In his report ‘Methods for the Study of Pathogenic Organisms’ Koch listed what are now known as ‘Koch’s Postulates’. The postulates are conditions that must all be met in order to demonstrate that a specific bacterium causes disease. Koch’s study set the basis for bacteriology and ultimately demonstrated that the miasma theory was not credible. Ideological shifts away from the miasma theory were able to happen after the establishment of the germ theory. The germ theory demonstrated to medical professionals, public health officials, and the general public that disease was caused by bacteria and that germs could be transferred from one individual to another. Acceptance of this theory allowed for the discovery of many human pathogenic microorganisms. Through the discovery of several pathogenic microorganisms, there was an urge to find ways to reduce the likelihood of transmission. One of the ways found to reduce transmission was the act of handwashing.
For more information on Koch’s 1881 journal article see: http://www.asmusa.org/ccLibraryFiles/FILENAME/0000000223/1881p101.pdf
Koch’s Postulates: 
The bacteria/ pathogen must:
- Be present in all cases
- Be capable of being isolated in pure culture
- Cause the disease if the pure isolated organism is inoculated into a disease-free host
- be observable in the experimentally infected host
 Rebecca Davis. 2015. The Doctor Who Campaigned Hand-Washing and Briefly Saved Lives. National Public Radio. http://www.npr.org/sections/health-shots/2015/01/12/375663920/the-doctor-who-championed-hand-washing-and-saved-women-s-lives
 Brian Hurwitz, and Marguerite Dupree. “Why Celebrate Joseph Lister?” The Lancet 379.9820 (2012): e39-40. ProQuest. Web. 13 Dec. 2016.
 John Lackie. 2015. A Dictionary of Biomedicine. Oxford University Press. 502.
 Cornell SIPS-PPPMB. 2016. Koch’s Postulates. Youtube. https://www.youtube.com/watch?v=8X92IL48Niw.