Dear aspirant, 

Hope you are doing well. As per your query their are many books and it solely depends on exactly what terms the question paper will be made. If it is only microbiology then you can refer to the following books:

Medical Microbiology by David Greenwood

Microbiology by Prescott 

Mastering Microbiology by Dr. Shivika J Sethi.

Hope you find this helpful. Thank you.