Which of the following is NOT part of Koch's postulates? A) the microorganism is never found in healthy animals. B) the microorganisms is always found in diseased animals. C) the microorganism must cause disease in healthy animals. D) the microorganism must be isolated.

A) the microorganism is never found in healthy animals.

Explanation:

According to the Koch's postulates, pathogens or microbes are involved in every disease. These pathogens can be isolated from the infected animal and can be grown in pure culture. Then this pure culture must cause disease when they are injected in a healthy individual. Then the same pathogen can be isolated from the second host.

So the microorganism will be found in the healthy organism if the healthy organism is infected with that microorganism. Therefore the microorganism is never found in healthy animals is not the part of Koch's postulates.