How to design isolated DB for each client where each client has specific credentials

We are trying to have an isolated DB for each client with the same host, we are handling all the clients from a single service(don’t have service for each client).
Criteria which we want to consider is:

  1. Each client DB should have different credentials for access
  2. For every new request, we don’t want to create a new mongo client object
    Is it possible to connect to host with admin credentials and later connecting to DB with client specific credentials based on application we get?