polymyxinë

Polymyxins are a group of antibiotics primarily used to treat infections caused by Gram-negative bacteria. They are cyclic lipopeptides, meaning they have a fatty acid component attached to a peptide ring. The most commonly used polymyxins are polymyxin B and polymyxin E, also known as colistin.

These antibiotics work by disrupting the bacterial cell membrane. They bind to the lipopolysaccharide (LPS) on the outer membrane of Gram-negative bacteria, increasing its permeability. This leads to leakage of essential intracellular components and ultimately cell death. Polymyxins are bactericidal, meaning they kill bacteria rather than just inhibiting their growth.

Due to their potential for nephrotoxicity and neurotoxicity, polymyxins are typically reserved for severe infections caused by multidrug-resistant Gram-negative pathogens, such as Pseudomonas aeruginosa, Acinetobacter baumannii, and carbapenem-resistant Enterobacteriaceae. They are often administered intravenously or topically.

The emergence of resistance to polymyxins is a growing concern. Resistance mechanisms can involve modifications to the LPS structure, making it less attractive to the antibiotic. Careful stewardship and appropriate use are crucial to preserve the effectiveness of this important class of antibiotics.