Multi-use facility cleaning, use of "penicillin" as a resistance marker

Hopefully, I’ll receive some positive “feedback” on my question/issue.

My facility is multi-use bacterial fermentation/purification. Typically, the majority of our work revolves around mfg of IVD components (enzymes/proteins for test kits). We do a “small” amount of work that might take a company in “discovery mode” up to Phase 1 clinicals, but not beyond.

The issue is we continue to receive “requests” to perform work where penicillin is used as the resistance marker in the expression system for the microbe. We have never allowed “pennicillin” in the facility, due to concerns related to “cleaning validation” for elimination of this compound.

We are of course talking about “microgram/ml” quantities here, but no matter the “logic”, we would be responsible for “proving elimination” of penicillin on all effected equipment, should we pursue work in this arena.

My questions are as follows:

1.) Is there a method available that lends itself to testing of residual penicillin, that we could apply in cleaning validation/verification? (this would include analogs, as well)
2.) Are we "over-thinking this? We would use “trace amounts” relatively speaking (50-100 micrograms/ml). We’re not a facility that mfg’s “drugs”, does the fact that we simply open a bottle of penicillin in our facility, put us at risk by CFR & CGMP?
3.) Should we just hold our stance, and refuse “work” in this arena? It is a lot of potential work, hate to pass it up…

Looking forward to a response… Would like to either put this issue to test once and for all w/ management, or find a “Validatable” way to enter this arena and do it RIGHT!