Koch's postulates (or Henle-Koch postulates) are four criteria designed to establish a causal relationship between a causative microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884 and refined and published by Koch in 1890. Koch applied the postulates to establish the etiology of anthrax and tuberculosis, but they have been generalized to other diseases. A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... The term disease refers to an abnormal condition of an organism that impairs function. ... Robert Koch For the American lobbyist, see Bobby Koch. ... He was the one who discovered the cause of FMD or Foot-and-Mouth Diesease. ... 1884 (MDCCCLXXXIV) is a leap year starting on Tuesday (click on link to calendar) of the Gregorian calendar (or a leap year starting on Thursday of the 12-day-slower Julian calendar). ... 1890 (MDCCCXC) was a common year starting on Wednesday (see link for calendar) of the Gregorian calendar (or a common year starting on Friday of the Julian calendar). ... Etiology (alternately aetiology, aitiology) is the study of causation. ... Tuberculosis (abbreviated as TB for Tubercle Bacillus) is a common and deadly infectious disease that is caused by mycobacteria, primarily Mycobacterium tuberculosis. ...

The Postulates

Koch's postulates are:

1. The microorganism must be found in all organisms suffering from the disease, but not in healthy organisms.
2. The microorganism must be isolated from a diseased organism and grown in pure culture.
3. The cultured microorganism should cause disease when introduced into a healthy organism.
4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

However, Koch abandoned the second part of the first postulate altogether when he discovered asymptomatic carriers of cholera (Koch, 1893) and later, Typhoid Mary. Indeed, asymptomatic carriers of many diseases have since been found, especially viruses such as polio, herpes simplex, HIV and hepatitis C. As a specific example, all doctors and virologists agree that poliovirus causes paralysis in just a few infected subjects, and the success of the polio vaccine in preventing disease supports the conviction that the poliovirus is the causative agent. Epithelial cells in culture, stained for keratin (red) and DNA (green) Cell culture is the term applied when cells are grown in a synthetic environment. ... Cholera (frequently called Asiatic cholera or epidemic cholera) is a severe diarrheal disease caused by the bacterium Vibrio cholerae. ... Mary Mallon (September 23, 1869 – November 11, 1938), also known as Typhoid Mary, was an Irish immigrant who was the first known healthy carrier of typhoid fever in the United States. ... In medicine, a disease is asymptomatic when it is at a stage where the patient does not experience symptoms. ... Poliomyelitis (polio), or infantile paralysis, is a viral paralytic disease. ... This article is about the disease. ... Species Human immunodeficiency virus 1 Human immunodeficiency virus 2 Human immunodeficiency virus (HIV) is a retrovirus that causes acquired immunodeficiency syndrome (AIDS, a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections). ... Hepatitis C is a blood-borne, infectious, viral disease that is caused by a hepatotropic virus called Hepatitis C virus (HCV). ... Two polio vaccines are used throughout the world to combat polio. ...

The third postulate does not hold true, as Koch himself discovered and stated in regard to both tuberculosis and cholera (Koch, 1884). Indeed, we see this today with diseases such as HIV, where CCR5 Δ32 deletion individuals seem to be resistant to infection with HIV. Tuberculosis (abbreviated as TB for Tubercle Bacillus) is a common and deadly infectious disease that is caused by mycobacteria, primarily Mycobacterium tuberculosis. ... Cholera (frequently called Asiatic cholera or epidemic cholera) is a severe diarrheal disease caused by the bacterium Vibrio cholerae. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...

History

Koch's postulates were developed in the 19th century as general guidelines to identify pathogens that could be isolated with the techniques of the day.^[1] Even in Koch's time, it was recognized that some infectious agents were clearly responsible for disease in spite of the fact that they did not fulfill all of the postulates.^[2] Attempts to rigidly apply Koch's postulates to the diagnosis of viral diseases in the late 19th century, at a time when viruses could not be seen or isolated in culture, may have impeded the early development of the field of virology.^[3][4] Currently, a number of infectious agents are accepted as the cause of disease despite their not fulfilling all of Koch's postulates.^[5] Therefore, while Koch's postulates retain historical importance and continue to inform the approach to microbiologic diagnosis, fulfillment of all 4 postulates is not required to demonstrate causality. Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ... Virology, often considered a part of microbiology or of pathology, is the study of organic viruses: their structure and classification, their ways to infect and exploit cells to reproduce and cause disease, the techniques to isolate and culture them, and their potential uses in research and therapy. ...

Koch's postulates have also influenced scientists who examine microbial pathogenesis from a molecular point of view. In the 1980s, a molecular version of Koch's postulates was developed to guide the identification of microbial genes encoding virulence factors.^[6] Molecular Kochs postulates are a set of experimental criteria that must be satisfied to show that a gene found in a pathogenic microorganism encodes a product that contributes to the disease caused by the pathogen. ... Virulence is either the relative pathogenicity or the relative ability to do damage to the host of an infectious agent. ...

Notes

References

• Koch R. Über die Ätiologie der Tuberkulose. In: "Verhandlungen des Kongresses für Innere Medizin. Erster Kongress, Wiesbaden 1882".
• Koch R. (1884) Mitt Kaiser Gesundh 2, 1-88
• Koch R. (1893) J. Hyg. Inf. 14, 319-333