title: [Isolation and characteristics of polymyxin-resistant mutants of Shigella flexneri].
abstract: Some characteristics of S. flexneri 2a mutants resistant to various concentrations of polymyxin M were studied. The data indicate that mutations resulting in low (50 microgram/ml) and high (300 microgram/ml) levels of the antibiotic resistance were determined by different genes. Polymyxin resistance led to changed permeability of the outer membrane with respect to detergents and some antibiotics, such as aminoglycosides, penicillins, chloramphenicol and amphotericin B but did not change sensitivity of the strains to some bacteriophages, except phage PI. Mutants resistant to 50 microgram/ml of polymyxin M preserved their ability to induce keratoconjunctivitis in guinea pigs. Part of the strains resistant to 300 microgram/ml of the antibiotic lost this property. No correlation between the polymyxin M resistance level, loss of the pathogenic properties and toxicity of the bacterial cells was found. It was confirmed that though inactivation of endotoxin by polymyxins is associated with their capacity for interaction with lipid A, this component does not participate in development of resistance to these antibiotics.
mesh_terms: D000818:Animals; D001435:Bacteriophages; D004305:Dose-Response Relationship, Drug; D004352:Drug Resistance, Microbial; D051379:Mice; D008826:Microbial Sensitivity Tests; D009154:Mutation; D011113:Polymyxins / Q000037:antagonists & inhibitors*; D012763:Shigella flexneri / Q000187:drug effects / Q000302:isolation & purification*; D014774:Virulence / Q000187:drug effects
chemical_list: D011113:Polymyxins
vernacular_title: Poluchenie i kharakteristika polimiksinorezistentnykh mutantov shigell Fleksnera.