If I take only bsc in a college then after 3 years can I do MSc in other topic like microbiology although I didn't do bsc in microbiology

Yes you can do. The eligibility criteria may varies according to Universities. However the basic eligibility criteria of SGT University Gurugram is given below for an idea. Eligibility criteria of M.Sc. Microbiology : Must have passed B.Sc. (Microbiology)/ B.Sc. (Biological Sciences)/ B.Sc. (Life Sc