A last-line polycationic lipopeptide that targets lipid A of Gram-negative bacteria; on the WHO Essential Medicines List.
Also known as: PMB
Part of the Foundational & therapeutic peptides cluster
Overview
Polymyxin B is a cyclic lipopeptide antibiotic from Paenibacillus polymyxa, produced as a mixture of closely related components. Its cationic diaminobutyric acid residues bind the lipid A of lipopolysaccharide, permeabilizing the Gram-negative outer membrane. Approved since 1964 and on the WHO Essential Medicines List, it is used for serious Gram-negative infections and in topical combinations. This page is educational and not medical advice.
Source & context
Biological / chemical source: Soil bacterium Paenibacillus polymyxa (formerly Bacillus polymyxa)
Primary research or clinical context: Approved antibiotic for serious Gram-negative infections; also in topical products
Structure and mechanism
Polymyxin B is a cyclic heptapeptide with a tripeptide side chain bearing a fatty-acyl tail and several 2,4-diaminobutyric acid (Dab) residues. The positively charged Dab groups bind anionic lipid A, displacing stabilizing cations and dissolving into the membrane so that it leaks. It is inactive against Gram-positive bacteria.
Clinical role
Once limited by kidney and nerve toxicity, polymyxin B re-emerged as a treatment for multidrug-resistant Gram-negative infections such as those from Pseudomonas aeruginosa. It also appears in over-the-counter topical antibiotic ointments alongside bacitracin and neomycin. Systemic use requires clinical supervision.
FAQ about Polymyxin B
What is Polymyxin B?+
Polymyxin B is a cyclic lipopeptide antibiotic from Paenibacillus polymyxa, produced as a mixture of closely related components. Its cationic diaminobutyric acid residues bind the lipid A of lipopolysaccharide, permeabilizing the Gram-negative outer membrane. Approved since 1964 and on the WHO Essential Medicines List, it is used for serious Gram-negative infections and in topical combinations. This page is educational and not medical advice.
Is Polymyxin B an approved medicine?+
Polymyxin B: Approved antibiotic for serious Gram-negative infections; also in topical products. Always follow licensed medical guidance for approved products.
What is the typical length of Polymyxin B?+
Polymyxin B is not a classic amino-acid chain peptide in the same sense; see the profile for classification details.