The Romans already believed something very similar to germ theory: that diseases were caused by an invisible contagion that was passed through contact/exposure to those already infested by it.

Also, I would be the primary distributor and manufacturer of pennicillin; so I could have some control over how it was distributed. Ensuring it got into the hands first of medics trained in my courses -- I.e.; people who knew about germ theory -- would be trivial.

Plus, I'd have decades to resolve the issue.