title: Adaptive resistance to benzalkonium chloride, amikacin and tobramycin: the effect on susceptibility to other antimicrobials.
abstract: OBJECTIVE
  To produce strains of antimicrobial-resistant Pseudomonas aeruginosa via adaptation to benzalkonium chloride, amikacin and tobramycin and to then examine the incidence, or otherwise, of cross-resistance between antibiotics and between antibiotics and benzalkonium chloride.
  
  
  RESULTS
  Adaptation was obtained by progressive subculturing in subinhibitory concentrations of the antimicrobials. Pseudomonas aeruginosa NCIMB 10421 adapted to grow in high concentrations of benzalkonium chloride (BC) had lower MIC to antibiotics than the wild type, whereas Ps. aeruginosa adapted to grow in antibiotics had greater MIC to benzalkonium by a small degree.
  
  
  CONCLUSIONS
  Adaptive resistance to BC of Ps. aeruginosa generally produced cultures with a decrease in resistance to several antibiotics. Adaptive resistance to the aminoglycosides Ak and Tm produced a low-level increase in tolerance to BC. The adaptive mechanisms of resistance appear to be different for the different types of antimicrobials used.
  
  
  CONCLUSIONS
  The relationships between biocide and antibiotic resistance are complex. It appears, from this study, that an organism resistant to a common biocide can become sensitive to antibiotics, but the converse was not true. Could this observation be used in a strategy to alleviate antibiotic resistance?
authors.affiliation: Kings College London, Sharnbrook, Bedfordshire, UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Joynson
authors.forename: B
authors.initials: B
authors.lastname: Forbes
authors.forename: R J W
authors.initials: RJ
authors.lastname: Lambert
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects; D000583:Amikacin / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D008055:Lipids / Q000502:physiology; D008826:Microbial Sensitivity Tests; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D014031:Tobramycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D000891:Anti-Infective Agents, Local; D001548:Benzalkonium Compounds; D008055:Lipids; D000583:Amikacin; D014031:Tobramycin