Hii

Although it would depend on the university which you will apply to whether the allow students from Microbiology to purse forensic science or not. But talking about the basic eligibility, the candidates possesing a bachelors degree in relevent subjects like Forensic science , botany, zoology, physics, chemistry, biotechnology, Microbiology, B.Pharma, BDS or even applied science, are eligible for the MSc Forensic Science degreee. 
Now that you have BSc microbiology, you can apply for MSc forensic science if you fulfill other eligibility criteria which would be set by the university. Like the minimum marks required in the bachelors degree, the entrance exam etc.
So a simple answer to your question is yes you are eligible for MSc forensic science.
If you wish to know about any particular college or university, you can freely revert back and we would help you with the relevent details.

Thanks!