Is it possible for an entity to determine which persistence-unit (or session) it was loaded from?

I wrote routines to maintain an "audit trail" of all changes to entities, and they work great. However I want to ensure that they use the same persistence unit to save the audit trail, so that the audit tables and main entity tables are committed/rolled back together. I'm finding this difficult to achieve especially with entities loaded indirectly via properties.

Any advice?