Question

Although Koch's postualates present a logical framework for establishing a particular microbe as the cause of a disease, they cannot always be applied today because

A: virtually all pathogens have been identified
B: some causative disease agents cannot be grown in pure culture
C: molecular methods are much more reliable and rapid
D: it is unethical to use animals for medical testing

Answer 1

B: Some causative disease agents cannot be grown in pure culture. Koch's postulates, a set of criteria proposed by Robert Koch in the 19th century, provide a logical framework for establishing a particular microbe as the cause of a disease. However, they cannot always be applied today because some causative disease agents, such as viruses, cannot be grown in pure culture and can only be detected with molecular methods.

A, C and D are also true but B is the main reason that Koch's postulates cannot always be applied today.