by Chrystal Mahan

Created on: October 13, 2009   Last Updated: October 16, 2009

Paradigm Shifts and the Germ Theory of Disease

The germ theory of disease is a theory that proposes that micro organisms are the cause of many diseases. Although highly controversial when introduced, it is now a cornerstone of modern medicine, leading to such important innovations as hand washing and antibiotics.

The historical view is that disease was spontaneously generated instead of being created by micro organisms which grow by reproduction. Anton van Leeuwenhoek first observed micro organisms. John Snow believed that the germ theory explained outbreaks of cholera, in opposition to the prevailing miasma theory of cholera.

A true germ theory of disease was spearheaded by the study of fermentation by French chemist Louis Pasteur, (who was more interested in wine making), beginning in 1879 and shown in a paper on wound infections published by the German bacteriologist Robert Koch in 1879. In general, the theory held that a pathogenic organism must be present in every case of the disease; that this organism could be grown or "cultured" outside the infected body; that an animal inoculated with this culture would get the same disease; and that the organism could be found again in the inoculated animal and re-cultured. Some pathogens may not meet all of these conditions, but they are the boiler plate for explaining scientifically how disease happens (Bidale).

Louis Pasteur demonstrated that fermentation and the growth of micro organisms in nutrient broths were not caused by spontaneous generation. He exposed freshly boiled broths to air in vessels that contained a filter to stop all particles passing through to the growth medium; and even with no filter at all, with air being admitted via a long tube that would not pass dust particles. Nothing grew in the broths, therefore living organisms that grew in such broths came from outside, as spores on dust, rather then being generated with the broth.

This discovery was a huge shift in the medical world. Louis Pasteur found a cure for chicken cholera, anthrax and rabies. He got doctors and surgeons to sterilize everything they used. He once and for all proved that germs existed and that they carried disease. But, Louis Pasteur's main contributions to microbiology and the world of medicine were much more then just those basics. Hospitals began instituting changes in their medical practices to minimize the spread of disease by microbes or germs. He discovered that the weak forms of disease could be used as an immunization

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