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Koch's postulates

Koch's postulates

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Koch's postulates

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  1. Koch’s Postulates Dr.T.V.Rao MD Dr.T.V.Rao MD

  2. A tribute to Robert Koch • Robert Koch, a German scientist born in 1843, is considered by many to be the founder of bacteriology. • As the District Medical Officer, one of Koch’s primary concerns was the prevalent occurrence of anthrax among farm animals in his area. • After converting his 4-room home into his own medical laboratory stocked only with a single microscope, Koch set to determining the cause of this virulent disease. Dr.T.V.Rao MD

  3. Robert Koch1843 - 1910 • A German scientist • Formulated the Bacteriological techniques • Staining Methods • Discovered the Mycobacterium and Vibrio cholera Dr.T.V.Rao MD

  4. Microbes and humans Very few microbes are always pathogenic Many microbes are potentially pathogenic Most microbes are never pathogenic Dr.T.V.Rao MD

  5. How do we know that a given pathogen causes a specific disease? Diagnosis and effective treatment of infection depends not just on isolating an organism, but in establishing a plausible link between the laboratory findings, recognised syndromes and the patient's clinical condition Recognised syndromes e.g. septicaemia, endocarditis, osteomyelitis meningitis, UTI, pneumonia pharyngitis patient's clinical condition potential pathogen isolated from or detected in clinical samples Dr.T.V.Rao MD

  6. Koch's postulates the pathogen must be present in every case of the disease the pathogen must be isolated from the diseased host & grown in pure culture the specific disease must be reproduced when a pure culture of the pathogen is inoculated into a healthy susceptible host the pathogen must be recoverable from the experimentally infected host How do we know that a given pathogen causes a specific disease? Dr.T.V.Rao MD

  7. Robert Koch’s hypothesis • Koch hypothesized that anthrax bacillus, a gram positive bacterium, was the cause of the anthrax disease. • Koch proved his hypothesis correct by infecting mice with the bacillus strains taken from the spleens of animals who died from the disease. • When the infected mice showed identical symptoms, Koch proved his hypothesis correct. • Koch then sought to prove that anthrax that had no prior contact with animals could cause the same disease when introduced to an animal host. • Koch grew the bacilli in pure cultures over several generations; he then showed that they could still cause anthrax in later generations. Dr.T.V.Rao MD

  8. Robert Koch • Koch perfected his methods of diagnostics and expanded on the work of others. • Koch invented the method of cultivating bacteria on nutrient mediums, using potatoes as his source of nutrients for bacteria, and created a medium that could be stored in dishes created by his colleague Petri. • Koch’s work on diseases and diagnostics culminated with the creation of what are now known as Koch’s Postulates. • Koch’s Postulates are the 4 steps necessary to confirm if a suspected pathogen is indeed the cause of a disease.: Dr.T.V.Rao MD

  9. Robert Koch clarifies with hypothesis • First to Prove that bacteria caused disease. • Anthrax broke out in local cattle. • Found the agent Bacillus anthracis by an experimental process now known as Koch’s postulates Dr.T.V.Rao MD

  10. Koch's Postulates 1. Microorganisms are isolated from dead animals 2. Microorganisms are grown in pure culture 2b. Microorganisms are identified 3. Microorganisms are injected into healthy animals 4. Disease is reproduced in second animal 5. Microorganisms are grown in pure culture 5b. Identification of identical microorganism. Dr.T.V.Rao MD

  11. Dr.T.V.Rao MD Figure 14.3 - Overview

  12. Dr.T.V.Rao MD Figure 14.3, steps 1–2

  13. Dr.T.V.Rao MD Figure 14.3, steps 3–4

  14. Dr.T.V.Rao MD 5

  15. Exceptions to Koch’s Postulates • Microorganisms that are unable to be cultured on artificial media • (example: Treponema pallidum) • 2 or more organism work in synergy to cause a disease. • Symptoms and diseases can be causes by any one of several microbes. Dr.T.V.Rao MD

  16. Understating Severity or Duration of a Disease • Not all disease behaves the same! • Diseases vary widely in their onset, duration, and level of activity • Disease Classifiers: • Acute disease: Symptoms develop rapidly and tend to be more severe • Chronic disease: Disease develops slowly and are less severe • Subacute disease: Symptoms between acute and chronic • Latent disease: Disease with a period of no symptoms when the causative agent is inactive • The host has the disease but has subclinical symptoms Dr.T.V.Rao MD

  17. Programme created by Dr.T.V.Rao MD for Medical and Paramedical students in the Developing World • Email • doctortvrao@gmail.com Dr.T.V.Rao MD

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