Germ theoryIdea that microorganisms may cause diseaseThe discovery that microorganisms, like yeast could cause changes in organic materials alerted scientist to think about the idea that microorganisms could potentially cause changes in plants and animals (us!)Like Biogenesis the Germ theory was a difficult concept for most
The Germ Theory of Disease1835: Agostino Bassi showed that a silkworm disease was caused by a fungus.1865: Pasteur believed that another silkworm disease was caused by a protozoan.1840s: Ignaz Semmelwise advocated hand washing to prevent transmission of puerperal fever from one OB patient to another.
Joseph ListerBegan applying germ theory to medical proceduresHe knew that phenol solutions kills bacteria, so he began treating surgical wounds with phenolReduced infections dramaticallyFindings proved that microorganisms cause surgical wound infections
Robert KochKoch provided the first proof that bacteria causes disease when he discovered Bacillus anthracis caused anthraxHe designed a sequence of experimental steps for directly relating a specific microbe to a specific disease
Koch’s ExperimentMicroorganisms (MO) are isolated from a dead animalThe MO are grown in pure culture and identifiedThen the MO are injected into a healthy animalThe disease is reproduced in the second animal; MO are isolated againMO are grown in pure culture and identified as the same MO from the first dead animal
From this experiment, Koch derived a set of criteria to discern the origin of a disease Koch’s Postulates
Exception’s to Koch’s PostulatesSome microbes have unique culture requirementsTreponema pallidumhas never been cultured on artificial mediaSome infectious diseases are not as clear-cutNephritis can be caused by several MO’sSome MO’s can cause several diseasesStreptococcus pyogenescans cause sore throat, skin infection, and other diseases