Koch's Postulates and the Etiology of Rickettsial Diseases
Koch's Postulates and the Etiology of Rickettsial Diseases VICTORIA A. HARDEN Downloaded from ! N his famous 1882 paper on the etiology of tuberculosis, Robert Koch described the procedures that were neces- sary and sufficient to demonstrate bacterial causation for tuberculosis, and by extension, for other bacterial diseases as well. He stated: "It was necessary to isolate http://jhmas.oxfordjournals.org/ the bacilli from the body, to grow them in pure culture until they were freed from any disease-product of the animal organism which might adhere to them; and, by administering the isolated bacilli to animals, to reproduce the same morbid condition which, as known, is obtained by inoculation with spontaneously developed tuberculous material."1 These criteria, which became known as "Koch's postulates," were predicted on the assumption that microbial pathogens were living at University of Michigan on June 19, 2015 cells with predictable behaviors. The second imperative—to obtain a pure culture of the organism—was of key importance, and a "pure cul- ture" was generally accepted to mean a colony of organisms grown on lifeless media, especially on the solid gelatin media developed by Koch himself. Even at the time Koch stated the postulates, the "viruses," or infectious agents, of many diseases—especially those that were invisible under the microscope and passed through filters—could not be cultured 1. Robert Koch, "Die Aetiologie der Tuberculose," Berl. klin. Wchnschr. 19:221-230, 1882, trans. Dr. and Mrs. Max Pinner, idem, The Aetiology of Tuberculosis, New York, National Tuberculosis Association, 1922, quotation from p. 31. Lester S. King, in "Dr.
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