Antimicrobial
Polymyxins (colistin)
Cationic outer-membrane detergent
pol-ee-MIX-ins
High-yield clue
Polymyxins bind lipid A of LPS and disorganize the Gram-negative outer membrane, and mcr-1 is the transferable resistance gene concept.
Overview
A cationic cyclic-peptide class (colistin/polymyxin E, polymyxin B) studied as a last-resort Gram-negative agent that disrupts the outer membrane by binding lipid A of LPS.
Classification
- Cationic cyclic peptide
- Binds lipid A of lipopolysaccharide
- Membrane-permeabilizing / bactericidal
- Aerobic Gram-negative spectrum
Lab & identification clues
- Outer-membrane disruption / LPS binding concept
- Plasmid-borne mcr-1 resistance vocabulary
- Broth microdilution testing preference concept
Associations
- Carbapenem-resistant Gram-negative reserve vocabulary
- Nephrotoxicity and neurotoxicity study framing
- Intrinsic resistance in Proteus and Serratia concept
Commonly confused with
- Lipopeptides (daptomycin)
- Aminoglycosides
Your notes
Original mechanism summary for microbiology study. Sources checked: CDC antimicrobial-resistance guidance, NCBI Bookshelf Medical Microbiology, and standard coursework frameworks; reviewed 2026-06. Covers class, mechanism, and resistance vocabulary only; no prescribing, dosing, or patient-specific treatment guidance.