Polypeptide Antibiotics
Overview
Polypeptide antibiotics are a class of antimicrobial agents composed of amino acid chains that exert their bactericidal activity through various mechanisms, primarily targeting the bacterial cell membrane.
Cyclic Peptide Antibiotics
Bacitracin
- Classification: Cyclic peptide antibiotic
- Mechanism of Action: Interferes with dephosphorylation in the bacterial cell wall synthesis pathway
- Spectrum: Primarily active against Gram-positive bacteria
- Clinical Use:
- Topical applications (skin infections)
- Limited systemic use due to nephrotoxicity
- Adverse Effects: Nephrotoxicity when used systemically
Cycloserine
- Classification: Cyclic peptide antibiotic
- Mechanism of Action: Inhibits bacterial cell wall synthesis by blocking enzymes involved in peptidoglycan formation
- Spectrum: Active against Mycobacterium tuberculosis
- Clinical Use: Second-line treatment for tuberculosis
- Adverse Effects:
- CNS toxicity (seizures, psychosis)
- Peripheral neuropathy
Mechanism Summary
Polypeptide antibiotics typically work by:
- Disrupting cell membrane integrity causing cell leakage
- Inhibiting cell wall synthesis enzymes
- Interfering with essential bacterial metabolic processes
Clinical Considerations
- Narrow therapeutic index requires careful monitoring
- Significant toxicity limits systemic use
- Primarily topical applications for most polypeptide antibiotics
- Resistance development is relatively uncommon but can occur