Which of the following is the most important element of Koch’s germ theory of disease? The animal shows disease symptoms when

a. the animal has been in contact with a sick animal.

b. the animal has a lowered resistance.

c. a microorganism is observed in the animal.

d. a microorganism is inoculated into the animal.

e. microorganisms can be cultured from the animal.

Video transcript

Hi, everyone. Let's take a look at this practice problem together, Robert Cook's postulate has four criteria including the following. Except the answer. Options are a, the microorganism must be found in disease but not in healthy individuals. B the microorganism must be cultured from the diseased individual. See, inoculation of a healthy individual with a cultured microorganism should recapitulate the disease. D the micro organism must be re isolated from the inoculated diseased individual and matched to the original microorganism and option E, none of the above. Now recall that cook's postulates are criteria that establish whether a particular organism causes a particular disease. Now, options A through D are the four criteria and they do appear in the correct order. So let's discuss them. Option A is the first criteria that the micro organism must be found in diseased individuals but not healthy ones. So the microorganism must be found in all diseased individuals. Option B is the second criteria, the micro organism must be cultured from the diseased individual. So you must be able to isolate the microorganism and be able to grow a pure culture of it. Option C is the third criteria when you introduce a healthy individual to the cultured microorganism, they should develop the disease. And the fourth criteria is option D, you must be able to re isolate the microorganism from the inoculated individual. And that re isolated microorganism must be matched to the original one. And this confirms the microorganism is the cause of the disease. So options A through D are the criteria of cook's postulates the correct answer and the exception therefore is option E, none of the above. So the correct answer is option E none of the above. All right, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.