title: Inactivation of endotoxin by polymyxin B.
abstract: The limulus gelation assay was utilized to investigate endotoxin inactivation by a number of antibiotics in vitro. Endotoxin activity was sharply reduced by polymyxin B and sodium colistimethate. The effect of the polymyxin was not significantly inhibited by 0.001 M calcium or 90% serum. Crude endotoxins from a variety of aerobic gram-negative bacteria, including several not previously studied, could be inactivated 1 or more logs by as little as 1 mug of polymyxin B per ml, whereas Bacteroides fragilis endotoxin was poorly detoxified. A 10,000-fold range in the relative susceptibility of different endotoxins to inactivation by polymyxin B was found. The endotoxin most susceptible to polymyxin B was derived from an organism resistant to polymyxin B by disk sensitivity testing, suggesting that the bacteriocidal and endotoxin detoxifying properties of polymyxin need not be directly related.
mesh_terms: D004731:Endotoxins / Q000037:antagonists & inhibitors*; D006090:Gram-Negative Bacteria / Q000737:chemistry*; D011112:Polymyxin B / Q000494:pharmacology*
chemical_list: D004731:Endotoxins; D011112:Polymyxin B