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Polymyxins are antibiotics, with a general structure consisting of a cyclic peptide with a long hydrophobic tail. They disrupt the structure of the bacterial cell membrane by interacting with its phospholipids. They are produced by nonribosomal peptide synthetase systems in Gram-positive bacteria such as ''Paenibacillus polymyxa'' and are selectively toxic for Gram-negative bacteria due to their specificity for the lipopolysaccharide molecule that exists within many Gram-negative outer membranes. Polymyxins B and E (also known as colistin) are used in the treatment of Gram-negative bacterial infections. The global problem of advancing antimicrobial resistance has led to a renewed interest in their use recently.〔Falagas ME, Grammatikos AP, Michalopoulos A. Potential of old-generation antibiotics to address current need for new antibiotics. Expert Rev Anti Infect Ther. 2008; 6(5):593-600 PMID 18847400〕 Polymyxin M is also known as "mattacin". == Clinical use == Polymyxin antibiotics are relatively neurotoxic and nephrotoxic, so are usually used only as a last resort if modern antibiotics are ineffective or are contraindicated. Typical uses are for infections caused by strains of multiple drug-resistant ''Pseudomonas aeruginosa'' or carbapenemase-producing Enterobacteriaceae. Polymyxins are not absorbed from the gastrointestinal tract, so another route of administration must be chosen, e.g., parenteral (often intravenously) or by inhalation (unless perhaps the targets are bacteria in the gastrointestinal tract). They are also used externally as a cream or drops to treat otitis externa (swimmers ear).〔Staff, Medicine.net. Last reviewed 16 April 2014 (Neomycin/polymyxin/hydrocortisone suspension - otic, Cortisporin, Pediotic )〕 Polymixin B is a component of triple antibiotic ointment. Polymyxins have less effect on Gram-positive organisms, and are sometimes combined with other agents (as with trimethoprim/polymyxin) to broaden the effective spectrum. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Polymyxin」の詳細全文を読む スポンサード リンク
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