Peptide antibiotics are a unique class of antimicrobial agents composed of amino acid chains. While many traditional antibiotics are small molecules, these peptides often function by disrupting the physical integrity of bacterial cell membranes. They are categorized primarily into non-ribosomal peptides and antimicrobial peptides (AMPs).
Mechanism of Action: Pore Formation and Lysis
Many peptide antibiotics, such as Polymyxins and Daptomycin, utilize a "detergent-like" mechanism.
Binding: The positively charged (cationic) peptide is attracted to the negatively charged components of the bacterial cell wall (such as Lipopolysaccharides in Gram-negative bacteria).
Insertion: The peptide inserts its hydrophobic tail into the lipid bilayer.
Pore Formation: As multiple peptides aggregate, they form physical channels or "pores." This causes the leakage of essential intracellular ions (like Potassium), leading to the immediate loss of membrane potential and cell death.
Clinical Significance
Due to their ability to physically rupture membranes, bacteria find it significantly harder to develop resistance against these agents compared to metabolic inhibitors. However, because of their potential toxicity to human cell membranes, several peptide antibiotics (like Bacitracin) are restricted to topical applications, while others (like Colistin) are reserved as "last-resort" treatments for multi-drug resistant infections.