I had something to say when he mentioned "antibiotic" like it was just one thing (no doubt it'd be penicillin without examining the patient indeed), but then...

... fuck it. Bring on the penicillin. It's probably the only thing he can make anyway so why the hell not. Most people who've read a bit about penicillin know it comes from a mould, but no one has a clue about how cephalexin, vancomycin, ciprofloxacin or meropenum are made (including myself).

So for story's sake.. yeah, let's just keep it to penicillin. The bigger issue is going to be dosing.