Ancient Entries in passdb

All, I have an interesting one for you. I'm doing some maintenance on my OD server (demote, promote, kerberize, etc) which was migrated from a 10.3 -> 10.4 -> 10.5 (now running 10.5.6). During the kerberize process (done to see if I can fix some users not having kerberos entries for their accounts), I notice a not of accounts being listed that have LONG since been deleted from the system, but apparently are still taking up spots in the passdb? Any way to prune the database to remove these, and free up the slots in the database? There are literally thousands (perhaps 10's of thousands) of them. Thanks!