title: Cross-resistance to antibiotics of Escherichia coli adapted to benzalkonium chloride or exposed to stress-inducers.
abstract: OBJECTIVE
  To study the effects of adaptation and stress on the resistance to benzalkonium chloride (BC) and cross-resistance to antibiotics in Escherichia coli.
  
  
  RESULTS
  Precultivation of E. coli ATCC 11775 and E. coli DSM 682 in the presence of subinhibitory concentrations of BC or stress inducers (salicylate, chenodeoxycholate and methyl viologen) resulted in higher minimum inhibitory concentration (MIC) of BC and chloramphenicol (CHL). Adaptation to growth in sixfold of the initial MIC of BC resulted in stable BC resistance and enhanced tolerance to several antibiotics and ethidium bromide (EtBr). The MIC of CHL increased more than 10-fold for both strains. Enhanced efflux of EtBr in adapted E. coli ATCC 11775 indicated that the observed resistance was due to efflux. Changes in outer membrane protein profiles were detected in the BC-adapted cells. There were no indications of lower membrane permeability to BC.
  
  
  CONCLUSIONS
  Induction of stress response or gradual adaptation to BC or CHL results in acquired cross-tolerance between BC and antibiotics in E. coli. Enhanced efflux was one of the observed differences in adapted cells.
  
  
  CONCLUSIONS
  Provided not taking due precautions, extensive use of disinfectants could lead to emergence of antibiotic-resistant isolates.
authors.affiliation: MATFORSK, Norwegian Food Research Institute, Oslo, Norway. solveig.langsrud@matforsk.no
authors.forename: S
authors.initials: S
authors.lastname: Langsrud
authors.forename: G
authors.initials: G
authors.lastname: Sundheim
authors.forename: A L
authors.initials: AL
authors.lastname: Holck
mesh_terms: D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000187:drug effects; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D002701:Chloramphenicol / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000502:physiology*; D024901:Drug Resistance, Multiple, Bacterial / Q000502:physiology; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D004996:Ethidium / Q000493:pharmacokinetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D010539:Permeability / Q000187:drug effects; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D000891:Anti-Infective Agents, Local; D001425:Bacterial Outer Membrane Proteins; D001548:Benzalkonium Compounds; D002701:Chloramphenicol; D004996:Ethidium; D013752:Tetracycline