The German physician Robert Koch (1843-1910) established aprocedure for diagnosing causes of infection. In his research withanthrax, Koch developed the following four-step procedure, known asKoch’s postulates, as a guide for identifying specific pathogens.Biologists have used Koch’s postulates to identify manypathogens
- The pathogen must be found in an animal with the disease andnot in a healthy animal.
- The pathogen must be isolated from the sick animal and grown ina laboratory culture.
- When the isolated pathogen is injected into a healthy animal,the animal must develop the disease.
- The pathogen should be taken from the second animal and grownin laboratory culture. The pathogen should be the same as theoriginal pathogen.
Looking at the above statements, how is it possible that, inspite of being injected with a pathogen isolated from a sickanimal, another animal remains healthy?
A) There is not enough information to make a conclusion
B) The healthy animal immune system recognizes the pathogen asself
C) Such incident cannot happen – the injected animal will alwaysbe sick
D) Most likely, the other animal already encountered the especific pathogen and the animal is immune
