Germ Theory of Disease PDF

 spontaneous generation observations The Greek philosopher Aristotle (384–322 BC) articulated the theory of spontenous generation;This theory persisted into the 17th century, life arose from nonliving material if the material contained pneuma (“vital heat”). dust creates fleas, maggots arise...

 spontaneous generation observations The Greek philosopher Aristotle (384–322 BC) articulated the theory of spontenous generation;This theory persisted into the 17th century, life arose from nonliving material if the material contained pneuma (“vital heat”). dust creates fleas, maggots arise from rotting meat bread or wheat left in a dark corner produces mice Key experiments that disproved spontaneous generation Key experiments that disproved spontaneous generation Key experiments that disproved spontaneous generation Key experiments that disproved spontaneous generation Key experiments that disproved spontaneous generation Louis Pasteur‘s 1859 experiment is widely seen as having settled the question of spontaneous generation. He boiled a meat broth in a flask that had a long neck that curved downward, like that of a goose or swan. The idea was that the bend in the neck prevented falling particles from reaching the broth, while still allowing the free flow of air. The flask remained free of growth for an extended period. When the flask was turned so that particles could fall down the bends, the broth quickly became clouded. This work was so conclusive; that biology codified the “Law of Biogenesis,” which states that life only comes from previously existing life. Golden Age of Microbiology 1857- 1914 Beginning with Pasteur’s work, discoveries included the relationship between microbes and disease, immunity and antimicrobial medicine Germ Theory of Disease Germ theory states that specific microscopic organisms are the cause of specific diseases. Pasteur and The Germ Theory of Disease Pasteur showed that microbes are responsible for fermentation Microbial growth is also responsible for spoilage of food Pasteur demonstrated that spoilage bacteria could be killed with heat (pasteurization) Discovered that weak forms of disease could be used as an immunization against stronger forms and that rabies was transmitted by viruses too small to be seen under the microscopes of the time Developed vaccines for anthrax (1881)and rabies (1885) The Germ Theory of Disease: Robert Koch 1867: Robert Koch- provided proof that bacterium causes anthrax and provided the experimental steps, Koch’s postulates, used to prove that a specific microbe causes a specific disease. T Koch listed four criteria to determine that a certain germ causes a particular disease. These criteria are known as Koch's Postulates and are still used today Exceptions to Koch’s postulates 1. Many healthy people carry pathogens but do not exhibit symptoms of the disease. 2. Some microbes are very difficult or impossible to grow in vitro(in the laboratory) in artificial media. Eg. Treponema pallidum 3. Many pathogens are species specific. Eg. Brucella abortus cause abortion in animals but no report in humans. 4. Certain diseases develop only when an opportunistic pathogen invades immunocompromised host Germ Theory Summary Germ theory states that specific microscopic organisms are the cause of specific diseases. The theory was developed, proved, and popularized in Europe and North America between about 1850 and 1920. Because its implications were so different from the centuries– old humoral theory, germ theory revolutionized the theory and practice of medicine and the understanding of disease. Extra reading People that contributed to the germ theory of disease