Hello,

Dietitian and microbiology both are different subject. Dietitian mainly the course of nutrition and diet basis. And microbiology you have to know about the bacteria, fangi, viruses, protozoa etc.

You are completed you BSC in dietitian but you want to do MSc in microbiology. You can do it if you are getting 55% marks in your graduation degree. But I'll suggest you can go for MSc in food science or MSc in nutrition. It will be better because your subject will be change or not change but your course purpose will be same. Now choice is totally yours which subject you choose for masters degree.

All the best.