Bacitracin is composed of heptapeptide ring that is connected to a pentapeptide side chain and its related substances are governed by the type of N-terminal thiazoline ring and amino acids at positions X and Y in the polypeptide chain. The components designated as A, B1 and B2 are the most microbiologically active while the main degradation product is an inactive component F. Bacitracin has been deleted by the regulation 2821/98/EC from the list of approved animal feed additives (Directive 70/524/EEG Appendix B) and maximum residue limits in foodstuffs have been set (Regulation 37/2010/EC)

CD bacitracin ELISA is used for the quantitative analysis of zinc bacitracin residues in urine samples. The kit uses a polyclonal rabbit antibody which shows the following cross-reactivities:
+ zinc bacitracin (100%)
+ spiramycin ( <0.01%)
+ tylosin ( <0.01%)
+ virginiamycin ( <0.01%)
+ neomycin ( <0.01%)
+ chlortetracycline ( <0.01%)
+ olaquindox ( <0.01%)
The limit of detection (LOD) is 14.9 ng/g for urine samples (dilution).

Except for bacitracin, polypeptide antibiotics also include colistin and polymyxin B.
Colistin (polymyxin E) and polymyxin B are cationic polypeptide antibiotics that disrupt the outer bacterial cell membrane by binding to the anionic outer membrane and thereby neutralizing the bacteria’s toxicity and causing bacterial cell death.