title: Spontaneous antibiotic resistance mutation associated pleiotropic changes in Escherichia coli O157:H7.
abstract: Besides the well-known O157:H7 clone causing enterohaemorrhagic colitis and haemolytic uraemic syndrome in Europe, Japan and North America, the number of Escherichia coli isolates with non-motile (NM) phenotype has considerably increased. We supposed that spontaneous antibiotic resistance mutation could cause this phenotypic change. To model our hypothesis we isolated rifampicin--(Rif) and ampicillin--(Amp) resistant mutants from E. coli O157:H7 prototype strains 7785 and EDL933. Among Rifr mutants we could isolate strains with no or reduced motility, while the Ampr mutants became hypermotile. The biochemical profile of the mutants had not changed but phage sensitivity and generation time of the mutants were altered. Among the representative strains we did not find polymorphism with Southern blot analysis and no polymorphism was found in the fliC gene of the mutants. The described characteristics have proven to be stable. In a mice virulence assay by intravenous infections the virulence of the derivatives was also found to be changed. In summary, we found that the antibiotic-resistant phenotype in E. coli O157:H7 was coexpressed with several other phenotypic changes including motility and virulence. It can be assumed that expression of the involved phenotypes may be under the influence of a common regulatory cascade. Further work is needed to identify the components and mechanism of this regulatory system.
authors.affiliation: Veterinary Medical Research Institute of the Hungarian Academy of Sciences, H-1143 Budapest, Hungária krt. 21, Hungary. tothi@vmri.hu
authors.forename: I
authors.initials: I
authors.lastname: Tóth
authors.forename: Márta
authors.initials: M
authors.lastname: Csík
authors.forename: L
authors.initials: L
authors.lastname: Emódy
mesh_terms: D000372:Agglutination Tests; D000667:Ampicillin / Q000494:pharmacology; D000668:Ampicillin Resistance; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001434:Bacteriophage Typing; D002465:Cell Movement; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D004591:Electrophoresis, Polyacrylamide Gel; D004927:Escherichia coli Infections / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity* / Q000648:ultrastructure; D005408:Flagellin / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012293:Rifampin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D017931:DNA Primers; D004269:DNA, Bacterial; D005408:Flagellin; D000667:Ampicillin; D012293:Rifampin