Question

Same drug doesn't work against the microbes belonging into different groups. Why?

Answer 1

Taxonomically, all bacteria are closely related to each other but not to viruses and vice versa. This indicates that many important biochemical pathways are similar in bacteria. As a result, drugs that block one of the pathways in one member of a group is likely to be effective against many other members of the same group. But the same drug will not work against a microbe belonging to a different group (like viruses).

Answer 2

Because they have a cell cover which protects them