It wasn't on the list because I was being lazy and just answering the blackhead part of your post. I don't know much about bacitracin, except that it's im some turkey and chick starters as a preventative for necrotic enteritis. Google necrotic enteritits in poultry (Clostridium perfringens) and I'll think you'll find that it can be treated with metronidazole or amoxicillin.
-Kathy
Looked it up. Found it here: http://www.thepoultrysite.com/diseaseinfo/101/necrotic-enteritis
Thanks so much!