What is a key characteristic of polymyxins, such as colistin?

Polymyxins, including colistin, are primarily known for their ability to disrupt bacterial cell membrane integrity. They bind to the lipopolysaccharides and phospholipids in the outer membrane of Gram-negative bacteria, leading to increased membrane permeability and cell lysis. This mechanism of action is particularly effective against multi-drug resistant Gram-negative pathogens, making polymyxins a valuable treatment option in serious infections where other antibiotics may not be effective.

The other mechanisms described in the other options involve different classes of antibiotics. Inhibitors of DNA replication, such as fluoroquinolones, work by targeting DNA gyrase or topoisomerase. Antibiotics that block protein synthesis, like macrolides or tetracyclines, act on bacterial ribosomes to inhibit translation. Lastly, drugs that interfere with folic acid synthesis, such as sulfonamides, inhibit the enzymes involved in the folate pathway. Each of these classes has its unique mechanism, but it is the ability of polymyxins to disrupt the bacterial cell membrane that characterizes their action.