Does penicillin kill protozoa. if not, what microorganisms apart from bacteria does it work against?

Penicillin activity: Penicillin only kills bacteria. There are other types of germs -- viruses, fungi, protozoa and infectious proteins. For those, other treatments are involved. Penicillin these days has only a few uses, because of resistance (it's one of the oldest antibiotics still used) and the proliferation of other antibiotics that are in some ways easier to use. Talk to an ID doc or pharmacist to learn more.