RT Journal Article SR Electronic T1 An Instrument-free Method for the Demonstration of Efflux Pump Activity of Bacteria JF In Vivo JO In Vivo FD International Institute of Anticancer Research SP 657 OP 664 VO 20 IS 5 A1 MARTA MARTINS A1 BRUNO SANTOS A1 ANA MARTINS A1 MIGUEL VIVEIROS A1 ISABEL COUTO A1 ALEXANDRA CRUZ A1 THE MANAGEMENT COMMITTEE MEMBERS OF COST B16 OF THE EUROPEAN COMMISSION/EUROPEAN SCIENCE FOUNDATION A1 JEAN-MARIE PAGÈS A1 JOSEPH MOLNAR A1 SEAMUS FANNING A1 LEONARD AMARAL YR 2006 UL http://iv.iiarjournals.org/content/20/5/657.abstract AB The aim of the study was to develop a simple, inexpensive, reproducible ethidium bromide (EB)-agar based method that is independent of any specialized instrumentation, for the demonstration of efflux pump activity, which is responsible for antibiotic resistance of bacteria. Materials and Methods: A series of agar plates containing varying concentrations of EB were swabbed with strains of Escherichia coli or Staphylococcus aureus, which differed with respect to efflux pump activity. The plates were incubated at different temperatures and time periods and the measurements of fluorescence were used to evaluate the efflux activity of each culture. Results: This simple assay allowed us to identify the efflux of EB in different bacteria following an overnight incubation. The minimal concentration of EB that produced fluorescence was significantly greater at 37ÆC than at 4ÆC, suggesting the presence of an energy-dependent pump. The method was shown to simultaneously identify strains of a mixed culture that differed from each other with respect to the activity of their efflux pumps. Conclusion: The method, in conjunction with the use of antibiotic-containing disks, provides an additional advantage for the easy identification and selection of colonies that differ with respect to antibiotic susceptibility and degree of efflux pump activity. Because the method is very reproducible it may form the basis for interlaboratory standardization of efflux pump activity of multi-drug resistant (MDR) clinical isolates. Copyright © 2006 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved