Connect to Microsoft Access Database from XCode
You may try to use 3rd party tools that provide connectivity like actualtech one.http://www.actualtech.com/product_access.php
I personally never tried this one, but it looks promising.
I believe there are no native Microsoft support for other platforms than Windows.
If the database is in an MDB file, you could try using this online MDB to MySQL converter.
You could write a daemon that fetches the latest SQL dump daily or even hourly and stores it in a local SQLite file. Then your client app just needs to query the local file.
I know it's not as convenient as connecting to the database directly, but this is a 'free' solution.