I have done pharmacy, then MS in Microbiology and MBA and now unable to decide where I have to go and How?

Only you can really decide what you want to do for a PhD as it will be you spending 3-4 years of your life doing the research...

Well it all depends on what you want to end up doing. If your ultimate intention is to enter the business world, which your MBA qualification would lead me to suspect, then I'd forget the PhD and start job hunting. A PhD is a lot of work and at the end there's no guarantee that you'll be in a better position for employment than you are already.

If on the other hand you want to start a career in research (microbiology?) then a PhD is almost a necessity. With that in mind, you could either search for current PhD projects with funding attached or approach a university department directly, if you have a clear research proposal. You will probably have more success applying for an existing project as forming a research proposal is tough and requires a leap of faith from the point of view of your supervisor, that he/she may not be willing to take.

I would not consider applying into a research field, speciality, in which you have no experence. Start with what you know. Write your proposal based on what you have already done.

Thanks for advise
Actually the only research which I did in my m. Phil is on, Bioleaching of low grade shale ore by acidithibacillus ferrooxidans. This topic was decided accedently as I was ill and when I visited university No project was available except this. Then I develop interest and started doing that.
And now a days I am working to get paper pulished for that work. I want to do Ph.D, but I have more interest in medical sciences. Looking for scholarship as i cudn't do it without it.