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Video 23 in an introductory video series on antibiotics

Poly nixon’s are a group of basic peptides that were first discovered from the bacteria bacillus poly miksa there are two structurally similar poly mix-ins that are used clinically and their names are polymyxin b and colistin ie polymyxin e polymyxin b is made up of a ratio of polymyxin b 1 and b 2 polymyxin ii was first discovered from a different bacterial species

Bacillus colistin s colistin is the name given to polymyxin e when it is used for topical use and the name changes to call us to methane when polymyxin e is used intravenously an easy way to remember that both colistin and call us to methane are poly mix-ins is to remember that polymyxin ii was discovered from bacillus colistin as’ poly mix-ins were initially

Developed 50 years ago for their excellent gram-negative activity however they began to not be used as often as their systemic use had many adverse effects as recent antibiotic resistance increases in gram-negative bacteria poly mix-ins had begun to be utilized again clinically to combat the resistant bacteria poly mix-ins act at the surface of gram-negative

Bacteria to disrupt the membrane biochemically poly mix-ins are simple basic peptides that act as cationic detergents due to their amphipathic properties poly mix-ins are strongly attracted to the phospholipid bilayer that makes up the outer membrane of the gram-negative bacterium and when poly mix-ins interact with the phospholipid bilayer they disrupt and

Perturb the membrane in addition to disrupting the outer membrane of gram-negative bacteria poly mix-ins bind to and inactivate endotoxin this mechanism prevents endotoxin from being released into circulation hence protecting the body from the toxic effects of endotoxin these toxic effects include fever diarrhea and potential endo toxic shock ie septic shock poly

Mix-ins are bacteria scytl resistance to poly mix-ins is rare and has only really become a problem and extensively drug-resistant strains of klebsiella species and a scene bacter species gram-positive organisms are intrinsically resistant to poly mix-ins because gram positive bacteria do not possess an outer membrane like gram-negative bacteria poly mix-ins are

Known for their activity in gram-negative bacteria it is important to note that poly mix-ins are only active in gram-negative bacteria furthermore poly mix-ins are primarily active against a robes and not anaerobes poly mix-ins are active against santaro bacteria see pseudomonas species and a senior table actor species proteus species and sera tiye species are

Not sensitive to poly mix-ins lastly neisseria species burkholder o species as denote rofl minus species are resistant to poly mix-ins the relatively recent emergence of extensively antibiotic resistant strains including entero bacteria c pseudomonas aeruginosa and asuna toh vom oni has a renewed interest in systemic parental salvage polymyxin therapy topical

Administration of polymyxin such as an application to a superficial cut or scrape is well tolerated the lack of adverse effects after topical administration of poly mix-ins is due to an almost complete lack of systemic absorption from these application sites systemic parental administration of poly mix-ins is toxic and leads to dose dependent nephrotoxicity

Neurological adverse effects can accompany the nephrotoxicity these adverse effects include slurred speech vertigo paras thesis apnea and muscle weakness this concludes the video thanks for watching please direct any questions to me on twitter at cheeky underscore ryan i’ve also included my sources here thanks again

Transcribed from video
Polymyxins By Ryan Sheehy