ROBERT KOCH (1843- 1910)
Robert Koch, born on December 11, 1843, at Germany was a
practicing physician.
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1. Published that living, parasitic organisms
caused infectious diseases.
2. He devised the methods of
preparing, fixing and staining bacterial preparations by
aniline dyes.
3. He introduced the solid culture media
(using gelatin and agar) and the technique to isolate bacteria
in pure culture.
4. Discovered Mycobacterium tuberculosis
and Vibrio cholerae.
5. Demonstrated the pathogenicity,
growth and sporulation of anthrax.
6. Proposed the "Koch's
postulates" in his treatise on Mycobacterium
tuberculosis
7. Devised the old and new Tuberculin,
for delayed hypersensitivity.
8. Described the hypersensitivity reaction to
Mycobacterial antigen in guinea pig (Koch's
phenomenon).He is also revered as the "father of
Bacteriology" and was awarded the Nobel Prize in Medicine
and Physiology in 1905.
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Koch's postulates:
Robert Koch, in 1884
proposed a series of postulates in his treatise on Mycobacterium
tuberculosis and tuberculosis. These are:
1. The microorganism
should be found in all cases of disease in question and its distribution
should be in accordance with the lesion observed.
2. The
microorganism should be grown in pure culture in vitro for several
generations.
3. When such a pure culture is inoculated into
susceptible animal species, the typical disease must result.
4. The
microorganism must again be isolated from the lesions of such
experimentally produced disease.
Since late 19th century few
microorganisms did not meet the criteria of Koch's postulates. For
example Treponema pallidum (causative agent of Syphilis) and
Mycobacterium leprae (causative agent of leprosy) could not be
cultivated in vitro. Even though Neisseria gonorrhoeae
(causative agent of gonorrhoea) can be cultivated in vitro, no animal
model exists. Molecular cloning has made it possible to isolate as well
as modify specific genes associated with virulence and study them with
models of infection. Falkow, in 1988 proposed a set of molecular Koch's
postulates, which are:
1. The phenotype under investigation should be
associated with pathogenic members of a genus or pathogenic strains of a
species.
2. Specific inactivation of genes associated with the
virulence trait should lead to measurable loss in pathogenicity or
virulence.
3. Reversion or allelic replacement of mutated gene should
lead to restoration of pathogenicity.
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