Polypeptide Antibiotics

 Polypeptide antibiotics are a class of antimicrobial agents composed of short chains of amino acids (polypeptides). These antibiotics primarily target the bacterial cell membrane or cell wall, leading to disruption and bacterial death. Some common examples include:

• Polymyxins: They bind to the bacterial cell membrane of Gram-negative bacteria, increasing its permeability and causing cell lysis. Polymyxin B and colistin (polymyxin E) are widely used, especially against drug-resistant infections.

• Bacitracin: It interferes with cell wall synthesis in Gram-positive bacteria by inhibiting the transport of peptidoglycan precursors across the cell membrane.

Polypeptide antibiotics are typically used for topical applications due to their toxicity when administered systemically. However, in severe cases, some can be used intravenously under controlled conditions. Their use is often limited due to nephrotoxicity and neurotoxicity risks.