Select all the statements consistent with Koch's postulates:
a. The microorganism must be present in every case of the disease.
b. The microorganism must be re-isolated from the experimentally infected host and identified as being identical to the original specific causative agent.
c. The cultured microorganism should cause disease when introduced into a healthy host.
d. The microorganisms that do not induce the observed disease symptoms in experimental models should be eliminated.
e. The microorganism must be isolated from the diseased host and grown in pure culture.