n.
Any of various mainly toxic antibiotics derived from strains of the soil bacterium Bacillus polymyxa and used to treat various infections with gram-negative bacteria.
[New Latin polymyxa, specific epithet (POLY- + Greek muxa, slime) + -IN.]
polymyxin
Dictionary:
pol·y·myx·in (pŏl'ē-mĭk'sĭn) 
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| 5min Related Video: polymyxin |
| Food and Nutrition: polymyxins |
Antibiotics isolated from Bacillus polymyxin (B. aerosporin); polymyxin A is aerosporin. They are polypeptides, active against coliform bacteria; apart from clinical use, they are of value in controlling infection in brewing.
| Dental Dictionary: polymyxin |
(pol′ē-mik′sin)
n
n
An antibiotic substance derived from cultures of Bacillus polymyxa. Used topically, in troche form, in combination with bacitracin and neomycin in the treatment of various oral infections. Not used systemically; therefore sensitization is minimized. Systemic use may be attended by renal dysfunction and toxicity.
| Veterinary Dictionary: polymyxin |
A generic term for antibiotics derived from various strains of Bacillus polymyxa, several closely related compounds being designated by letters.
- p. B — a bacteriostatic and bactericidal antibiotic, effective mainly against gram-negative organisms. It is used as the sulfate salt, and is especially effective against Pseudomonas aeruginosa and is also used against Klebsiella spp. It is used mostly in combinations with other antibiotics as a topical dressing including ophthalmic and aural preparations. It is not absorbed from the alimentary tract and is not recommended for systemic use because of its nephrotoxicity and neurotoxicity.
- p. E — see colistin.
| Wikipedia: Polymyxin |
Polymyxins are antibiotics,[1] 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 the Gram-positive bacterium Bacillus polymyxa[2] 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.[3]
Polymyxin M is also known as "mattacin".[4]
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Mechanism of action
After binding to lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria, polymyxins disrupt both the outer and inner membranes. The hydrophobic tail is important in causing membrane damage, suggesting a detergent-like mode of action.
Removal of the hydrophobic tail of polymyxin B yields polymyxin nonapeptide, which still binds to LPS but no longer kills the bacterial cell. However, it still detectably increases the permeability of the bacterial cell wall to other antibiotics, indicating that it still causes some degree of membrane disorganization.
Gram-negative bacteria can develop resistance to polymyxins through various modifications of the LPS structure that inhibit the binding of polymyxins to LPS.[5]
Clinical use
Polymyxin antibiotics are considered relatively neurotoxic and nephrotoxic[6] and, though effective, are therefore used only if less toxic antibiotics are ineffective or are contraindicated. Typical use cases are infections with strains of Pseudomonas aeruginosa or Enterobacteriaceae species that are highly resistant to other types of antibiotics such as cephalosporins.
Polymyxins are not absorbed from the gastrointestinal tract and therefore must be administered intravenously.
Use in biomedical research
Polymyxins are used to neutralize or absorb LPS contaminating samples that are intended for use in e.g. immunological experiments. Minimization of LPS contamination can be important because LPS can evoke strong reactions from immune cells and therefore distort experimental results.
See also
References
- ^ Dixon RA, Chopra I (November 1986). "Polymyxin B and polymyxin B nonapeptide alter cytoplasmic membrane permeability in Escherichia coli". J. Antimicrob. Chemother. 18 (5): 557–63. doi:. PMID 3027012. http://jac.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=3027012.
- ^ MeSH Polymyxins
- ^ 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]
- ^ Martin NI, Hu H, Moake MM, et al. (April 2003). "Isolation, structural characterization, and properties of mattacin (polymyxin M), a cyclic peptide antibiotic produced by Paenibacillus kobensis M". J. Biol. Chem. 278 (15): 13124–32. doi:. PMID 12569104. http://www.jbc.org/cgi/pmidlookup?view=long&pmid=12569104.
- ^ Tran AX, Lester ME, Stead CM, et al. (August 2005). "Resistance to the antimicrobial peptide polymyxin requires myristoylation of Escherichia coli and Salmonella typhimurium lipid A". J. Biol. Chem. 280 (31): 28186–94. doi:. PMID 15951433. http://www.jbc.org/cgi/pmidlookup?view=long&pmid=15951433.
- ^ Falagas ME, Kasiakou SK (February 2006). "Toxicity of polymyxins: a systematic review of the evidence from old and recent studies". Crit Care 10 (1): R27. doi:. PMID 16507149. PMC 1550802. http://ccforum.com/content/10/1/R27.
Further reading
- Giuliani A, Pirri G, Nicoletto S (2007). "Antimicrobial peptides: an overview of a promising class of therapeutics". Cent. Eur. J. Biol. 2 (1): 1–33. doi:.
- Pirri G, Giuliani A, Nicoletto S, Pizutto L, Rinaldi A (2009). "Lipopeptides as anti-infectives: a practical perspective". Cent. Eur. J. Biol. 4 (3): 258–273. doi:.
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Food and Nutrition. A Dictionary of Food and Nutrition. Copyright © 1995, 2003, 2005 by A. E. Bender and D. A. Bender. All rights reserved. Read more |
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Mentioned in
- Polymyxin B
- Gramicidin; Neomycin; Polymyxin B
- Hydrocortisone; Neomycin; Polymyxin B
- Polymyxin B; Trimethoprim
- Neomycin; Polymyxin B
- Neomycin; Polymyxin B; Prednisolone
- Colistimethate, Colistin, Polymyxin E
- Aerosporin (microbiology)
- colistin
- Neomycin; Polymyxin B bladder irrigation
- Polymyxin B eye solution
- Bacitracin; Hydrocortisone; Neomycin; Polymyxin B topical ointment
- Antibiotics, Topical
- Neomycin; Polymyxin B; Prednisolone eye suspension
