Koch’s postulate for The Cause Effect Relationship
Health and disease are reciprocal concepts. Each is conventionally defined by the absence of the other. When micro organisms first associate with a host, the host is said to be contaminated.
If the micro organisms establish themselves and grow and multiply for a period of time, the host is said to be infected. If the infection causes damage, the host is said to have an infectious disease.
Micro organism should be identified to explain the etiology and pathogenesis of any infectious disease. It is necessary to introduce criteria for proving the claims that a micro organism isolated from a disease is indeed casually related to it. These criteria were first introduced by Henle and later on, defined by Koch and are known as “Koch’s postulates.”
According to Koch’s postulates, a micro organism should satisfy the following criteria if it is to be accepted as the causative agent of a particular disease. The criteria are,
a) The bacterium should be constantly associated with lesions of the disease
b) It should be possible to isolate the bacterium in pure culture from the lesion.
c) Inoculation of such pure culture into suitable laboratory animals should reproduce the same lesion of the disease
d) It should be possible to re-isolate the bacterium in pure culture from the lesions produced in the experimental animals.
Higher numbers of the suspected pathogens are found frequently in any infection rather than in individual without disease. As the root canal does not possess a normal microbiota all the microorganisms found are considered to be pathogenic. As long as the pulp is vital, it is a sterile tissue and infection occurs only after pulp necrosis. The micro organism present in the necrotic pulp is the source for the peri-radicular disease. Not all but only a few group of micro organisms in the root canal play a role in the pathogenesis of disease process .
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