Question

What are Koch’s postulates? Why are they not applicable to viruses?

Answer 1

Hint: According to Koch, there must be four conditions present for an organism to be a causative agent of a disease. He gave some postulates for pathogenic diseases which we call Koch’s postulates.

Complete answer: Robert Koch is a German scientist who was born in 1843, he is considered by many to be the founder of bacteriology. Koch converted his 4-room home into his own medical stocked only with a single microscope, Koch set to determine the cause of this virulent disease. -Koch in his hypothesis said that anthrax bacillus, a gram-positive bacterium, was the cause of the disease called anthrax. Koch proved his hypothesis correct by infecting mice with the bacillus strains that are taken from the spleens of different animals who died from the disease. When the infected mice showed identical symptoms, Koch proved his hypothesis correct. -Koch then tries to prove that anthrax that had no previous contact with animals could cause the same disease when introduced to an animal host. Koch grew the bacilli in pure cultures over many generations, he then showed that they could still cause anthrax in later generations which grow.
Let’s see 4 Koch’s postulates 1. The causative organism must be present in each disease and in case the organism is not present, there is a secondary cause of disease.
2. Pathogens must be able to be isolated from the diseased host & grown in culture.
3. When the isolated pathogen is introduced in a healthy person, it must infect that person.
4. The same organism must be isolated from the person who is experimentally infected.
Viruses do not follow Koch's postulates as they cannot be cultured in artificial media.

Note: Some exceptions to Koch’s postulates are as follows-
1. The microorganisms that are unable to be cultured on artificial media. (example: Treponema pallidum)
2. Symptoms and diseases can be caused by any one of several microbes