Why can polymyxin antibiotics be toxic to human cells?

Polymyxin antibiotics, including polymyxin B and polymyxin E (colistin), function by binding to phospholipids within the cell membrane of bacteria. This action disrupts the membrane's role as an osmotic barrier, causing essential macromolecules to leak out and leading to bacterial cell death.21

These antibiotics are toxic to human cells because human cells possess phospholipids that are similar or identical to those found in bacterial membranes. Consequently, polymyxins can react with human cell membranes, which may result in significant adverse effects, including kidney damage and neurotoxicity. Due to this lack of selective toxicity compared to other antibiotics, their clinical use is generally limited to cases where other treatments are ineffective.21