The main point here is that these medical devices must be sterile. So I assume they are produced in a cleanroom. Microbiology requirements then include the following:
Microbiology monitoring of the environment (surfaces, air, workers hand, machines that are used in the cleanroom)
Bioburden before sterilization so that you know what is the microbiological load of your products to know which sterilization method to choose
Testing the sterility of your product after the sterilization
All of this is stated in the following standard:
EN 556-1:2001 Sterilization of medical devices - Requirements for medical devices to be designated "STERILE" - Part 1: Requirements for terminally sterilized medical devices
The microbiology laboratory for performing all this work must be accredited. It is stated in the MDR 2017/745, Article 106 - Article 106 – Provision of scientific, technical, and clinical opinions and advice – that the EU Commission designated the expert laboratories. Accreditation is one way how a laboratory can be designated.