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koch s postulates

Koch’s Postulates

Dr.T.V.Rao MD

Dr.T.V.Rao MD

a tribute to robert koch
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

robert koch 1843 1910
Robert Koch1843 - 1910
  • A German scientist
  • Formulated the Bacteriological techniques
  • Staining Methods
  • Discovered the

Mycobacterium and

Vibrio cholera

Dr.T.V.Rao MD

microbes and humans
Microbes and humans

Very few microbes are

always pathogenic

Many microbes are

potentially pathogenic

Most microbes are

never pathogenic

Dr.T.V.Rao MD

how do we know that a given pathogen causes a specific disease
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


septicaemia, endocarditis,

osteomyelitis meningitis,

UTI, pneumonia


patient's clinical condition

potential pathogen isolated from or detected in clinical samples

Dr.T.V.Rao MD

how do we know that a given pathogen causes a specific disease6
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

robert koch s hypothesis
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

robert koch
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

robert koch clarifies with hypothesis
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

koch s postulates10
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

Dr.T.V.Rao MD

Figure 14.3 - Overview

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Figure 14.3, steps 1–2

Dr.T.V.Rao MD

Figure 14.3, steps 3–4

exceptions to koch s postulates
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

understating severity or duration of a disease
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


Programme created by Dr.T.V.Rao MD for Medical and Paramedical students in the Developing World

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  • doctortvrao@gmail.com

Dr.T.V.Rao MD