Polymyxins
Polymyxins
Polymyxins are a group of antibiotics that are particularly effective against Gram-negative bacteria. They are cyclic polypeptides with a long hydrophobic tail, and their primary mechanism of action is to disrupt the bacterial cell membrane. This class of antibiotics includes polymyxin B and polymyxin E (also known as colistin).
History[edit | edit source]
Polymyxins were first discovered in the late 1940s from the bacterium Bacillus polymyxa. They were initially used widely due to their effectiveness against Gram-negative bacteria, but their use declined with the development of less toxic antibiotics. However, with the rise of multidrug-resistant bacteria, polymyxins have regained attention as a last-resort treatment option.
Mechanism of Action[edit | edit source]
Polymyxins target the lipopolysaccharides (LPS) in the outer membrane of Gram-negative bacteria. By binding to the LPS, they disrupt the integrity of the bacterial cell membrane, leading to cell death. This mechanism is particularly effective against bacteria such as Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae.
Clinical Use[edit | edit source]
Polymyxins are primarily used to treat infections caused by multidrug-resistant Gram-negative bacteria. They are often considered antibiotics of last resort due to their nephrotoxicity and neurotoxicity. Polymyxin B is typically administered intravenously, while colistin can be administered intravenously or as an inhalation therapy for lung infections.
Side Effects[edit | edit source]
The use of polymyxins is associated with several side effects, the most significant being nephrotoxicity, which can lead to acute kidney injury. Neurotoxicity is also a concern, with symptoms ranging from dizziness and weakness to neuromuscular blockade.
Resistance[edit | edit source]
Resistance to polymyxins is a growing concern. Mechanisms of resistance include modifications to the LPS structure, which reduce the binding affinity of polymyxins. The emergence of the mcr-1 gene, which confers plasmid-mediated resistance to colistin, has been particularly alarming.
Also see[edit | edit source]
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