The same, unknown bacteria is isolated from 20 sick individuals. Their samples were grown in culture and then placed in 10 healthy mice. Those mice started to show signs of a heightened immune response. To determine if the bacteria is pathogenic, what is the next step by using Koch’s postulates?

A: Classify the bacteria as a noncommunicable disease.

B: Classify the bacteria as a communicable disease.

C: Reisolate it, and determine if it is the original unknown bacteria.

D: Treat the original 20 individuals with antibiotics.

The criteria that were designed to define a relationship between the microbe and the disease to understand the cause of it was laid down in terms of four postulates by Koch and Loeffler and is known as Koch's postulates.

The four criteria were as follows:

1. The microorganisms responsible for the disease must only be found in diseased organisms and not the healthy ones.

2. The microorganism should be isolated and then should be grown in pure culture.

3. The microorganism that is grown in pure culture should be able to cause the disease in healthy organisms.

4. The microorganism should then be reisolated and should be determined if it is the same as the original bacteria that is unknown.

Therefore, according to the given question the next ste pshould be the step 4 , i.e. Reisolate it, and determine if it is the original unknown bacteria.