Polypeptide Antibiotics: Bacitracin, Colistin, Polymyxin B By Brian J Werth, PharmD, University of Washington School of Pharmacy Reviewed / Revised May 2022 | Modified Sep 2022 View Patient Education Indications Contraindications Use During Pregnancy and Breastfeeding Adverse Effects Dosing Considerations Topic Resources Some Clinical Uses of Polypeptide... Polypeptide antibiotics disrupt bacterial cell walls.